Human Health Risk Assessment
EPA Has Taken Steps to Strengthen Its Process, but Improvements Needed in Planning, Data Development, and Training Gao ID: GAO-06-595 May 31, 2006Over 100,000 chemicals, pollutants, and toxic substances are used in the United States and regulated by the Environmental Protection Agency (EPA). EPA uses risk assessment to determine the health risk from exposure to these substances, collectively referred to as contaminants. In the last 12 years, independent reviewers have examined this process and made recommendations for how it could be improved. GAO was asked to (1) identify the significant recommendations that have been made to improve human health risk assessment; (2) describe what EPA has done to modify its human health risk assessment process; (3) determine the effects these past modifications have had on the preparation of risk assessments; and (4) identify any additional actions experts believe EPA could take to improve its process, and the barriers it would face in doing so.
Since 1994, independent reviewers recommended that EPA better plan its risk assessments. In doing so, they said EPA should better utilize scientific data it has and identify other data it needs on the potential adverse effects from exposure to contaminants, and prioritize and support research to meet those needs. Furthermore, reviewers recommended that EPA better evaluate the analytic tools it uses and employ more powerful tools when appropriate. Reviewers also recommended that EPA better analyze and characterize the sources of uncertainty in its risk assessments. Finally, they recommended that EPA enhance its analysis of variability in exposure to contaminants and in susceptibility to harm from exposure, and improve how it considers the effects of exposure to multiple contaminants and through many sources. EPA has strengthened its risk assessment process since 1994 and improvement efforts are ongoing. For example, EPA has increased planning for assessments and has initiated actions to develop missing or incomplete scientific data. EPA has also begun to embrace new methodologies, such as ones to predict how the body will react to a contaminant. Furthermore, EPA now uses a tiered approach to conducting uncertainty analysis, employing more sophisticated analysis as warranted. Finally, EPA has made progress in characterizing variability due to differences in both exposure and susceptibility of exposed individuals and has begun to take steps to address exposure to multiple contaminants and through multiple sources. According to EPA's risk assessors, the modifications EPA has made have generally helped improve risk assessments. Many EPA risk assessors believe that agencywide guidance has helped them prepare risk assessments and have resulted in greater consistency across program offices. Furthermore, while most assessors report collaboration with internal and external entities is effective and has improved the quality of risk assessments, some said conflicting priorities and poor communication hindered collaboration among some EPA offices. Finally, while risk assessors said training has helped them gain skills and knowledge, over 70 percent said that more in-depth or relevant training would improve their risk assessment abilities. Experts identified additional actions EPA could take to further improve its risk assessment process, recognizing that it may face barriers in doing so. Experts said EPA could improve its planning process by better focusing on scientific data needs and involving stakeholders early to obtain their concurrence with EPA's approach. Experts also said EPA could more thoroughly evaluate methods and models, transparently document its analytic choices, and enhance internal review. Finally, experts said EPA could provide additional training for risk assessors, managers, and stakeholders on the risk assessment process. Experts, however, said that the scientific complexity of risk assessment, the difficulty of obtaining and applying data, and a cultural resistance to deviating from established methods could act as obstacles to successfully making such changes.
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Report to the Chairman, Committee on Environment and Public Works, U.S.
Senate:
United States Government Accountability Office:
GAO:
May 2006:
Human Health Risk Assessment:
EPA Has Taken Steps to Strengthen Its Process, but Improvements Needed
in Planning, Data Development, and Training:
GAO-06-595:
GAO Highlights:
Highlights of GAO-06-595, a report to the Chairman, Committee on
Environment and Public Works, U.S. Senate
Why GAO Did This Study:
Over 100,000 chemicals, pollutants, and toxic substances are used in
the United States and regulated by the Environmental Protection Agency
(EPA). EPA uses risk assessment to determine the health risk from
exposure to these substances, collectively referred to as contaminants.
In the last 12 years, independent reviewers have examined this process
and made recommendations for how it could be improved. GAO was asked to
(1) identify the significant recommendations that have been made to
improve human health risk assessment; (2) describe what EPA has done to
modify its human health risk assessment process; (3) determine the
effects these past modifications have had on the preparation of risk
assessments; and (4) identify any additional actions experts believe
EPA could take to improve its process, and the barriers it would face
in doing so.
What GAO Found:
Since 1994, independent reviewers recommended that EPA better plan its
risk assessments. In doing so, they said EPA should better utilize
scientific data it has and identify other data it needs on the
potential adverse effects from exposure to contaminants, and prioritize
and support research to meet those needs. Furthermore, reviewers
recommended that EPA better evaluate the analytic tools it uses and
employ more powerful tools when appropriate. Reviewers also recommended
that EPA better analyze and characterize the sources of uncertainty in
its risk assessments. Finally, they recommended that EPA enhance its
analysis of variability in exposure to contaminants and in
susceptibility to harm from exposure, and improve how it considers the
effects of exposure to multiple contaminants and through many sources.
EPA has strengthened its risk assessment process since 1994 and
improvement efforts are ongoing. For example, EPA has increased
planning for assessments and has initiated actions to develop missing
or incomplete scientific data. EPA has also begun to embrace new
methodologies, such as ones to predict how the body will react to a
contaminant. Furthermore, EPA now uses a tiered approach to conducting
uncertainty analysis, employing more sophisticated analysis as
warranted. Finally, EPA has made progress in characterizing variability
due to differences in both exposure and susceptibility of exposed
individuals and has begun to take steps to address exposure to multiple
contaminants and through multiple sources.
According to EPA‘s risk assessors, the modifications EPA has made have
generally helped improve risk assessments. Many EPA risk assessors
believe that agencywide guidance has helped them prepare risk
assessments and have resulted in greater consistency across program
offices. Furthermore, while most assessors report collaboration with
internal and external entities is effective and has improved the
quality of risk assessments, some said conflicting priorities and poor
communication hindered collaboration among some EPA offices. Finally,
while risk assessors said training has helped them gain skills and
knowledge, over 70 percent said that more in-depth or relevant training
would improve their risk assessment abilities.
Experts identified additional actions EPA could take to further improve
its risk assessment process, recognizing that it may face barriers in
doing so. Experts said EPA could improve its planning process by better
focusing on scientific data needs and involving stakeholders early to
obtain their concurrence with EPA‘s approach. Experts also said EPA
could more thoroughly evaluate methods and models, transparently
document its analytic choices, and enhance internal review. Finally,
experts said EPA could provide additional training for risk assessors,
managers, and stakeholders on the risk assessment process. Experts,
however, said that the scientific complexity of risk assessment, the
difficulty of obtaining and applying data, and a cultural resistance to
deviating from established methods could act as obstacles to
successfully making such changes.
What GAO Recommends:
GAO recommends that EPA enhance early planning of each risk assessment,
identify and communicate data needs to the public and private research
community, and support development and implementation of in-depth
training for risk assessors and managers. EPA neither agreed nor
disagreed with our findings and recommendations. However, the agency
provided specific technical comments, which we incorporated as
appropriate.
[Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-06-595].
To view the full product, including the scope and methodology, click on
the link above. To view the results of GAO‘s survey of EPA‘s risk
assessors, click [Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-06-
637SP]. For more information, contact John Stephenson at (202) 512-6225
or stephensonj@gao.gov.
[End of Section]
Contents:
Letter:
Results in Brief:
Background:
Independent Reviewers Have Recommended Improvements to EPA's Risk
Assessment Process Since 1994:
EPA Has Strengthened Many Facets of Its Risk Assessment Process Since
1994, and Efforts Are Ongoing:
EPA Risk Assessors Responding to Our Survey Reported That Process
Modifications Have Helped Them Prepare Better Risk Assessments but That
Collaboration and Training Limitations Hamper Further Progress:
Enhanced Risk Assessment Planning, Improved Analysis and Review, and
Added Training Could Further Improve EPA's Process, but Barriers Could
Limit Progress:
Conclusions:
Recommendations for Executive Action:
Agency Comments:
Appendix I: Objectives, Scope, and Methods:
Appendix II: GAO Contact and Staff Acknowledgments:
Figures:
Figure 1: Typical Sequence of Risk Assessment and Risk Management
Processes:
Figure 2: Helpfulness of Office-Specific Guidance:
Figure 3: Risk Assessors That Generally or Strongly Agree That
Organizations Help Fill Data Needs:
Figure 4: Areas in Which Training Has Moderately or Greatly Improved
Risk Assessor Knowledge and Skills:
Figure 5: Types of Training Taken by Risk Assessors:
Figure 6: Modifications in Training That Would Moderately or Greatly
Improve the Preparation of Risk Assessments:
Abbreviations:
ASPH: Association of Schools of Public Health:
ATSDR: Agency for Toxic Substances and Disease Registry:
BOSC: Board of Scientific Counselors:
Commission: Presidential/Congressional Commission on Risk Assessment
and Risk Management:
CREM: Council for Regulatory Environmental Modeling:
EPA: Environmental Protection Agency:
FQPA: Food Quality Protection Act:
GIS: Geographic Information System:
HEI: Health Effects Institute:
HPV: High Production Volume:
ILSI-RSI: International Life Sciences Institute--Risk Science Institute:
IRIS: Integrated Risk Information System:
NAS: National Academy of Sciences:
NCCT: National Center for Computational Toxicology:
NCEA: National Center for Environmental Assessment:
NCER: National Center for Environmental Research:
NERL: National Exposure Research Laboratory:
NHEERL: National Health and Environmental Effects Research Laboratory:
NHEXAS: National Human Exposure Assessment Survey:
NIEHS: National Institute for Environmental Health Sciences:
NRMRL: National Risk Management Research Laboratory:
OAQPS: Office of Air Quality Planning and Standards:
OMB: Office of Management and Budget:
OP: Office of Pesticides:
OPPT: Office of Pollution Prevention and Toxics:
ORD: Office of Research and Development:
OW: Office of Water:
STAR: Science to Achieve Results:
TRIM: Total Risk Integrated Methodology:
TSCA: Toxic Substances Control Act:
United States Government Accountability Office:
Washington, DC 20548:
May 31, 2006:
The Honorable James M. Inhofe:
Chairman:
Committee on Environment and Public Works:
United States Senate:
Dear Mr. Chairman:
Chemicals play an important role in people's everyday lives. Consumers
use products containing chemicals, such as cleansers and pesticides,
and companies use a variety of toxic substances as solvents or
additives to their industrial processes. Although these substances have
beneficial uses and are important in producing goods and services, some
may adversely affect human health. Over 100,000 chemicals, pollutants,
and toxic substances are used in the United States and regulated by the
Environmental Protection Agency (EPA). These substances, whether
produced in the United States or imported, include 187 hazardous air
pollutants, nearly 20,000 pesticide products on the market, and a
growing number of substances used in industrial processes--over 82,000
as of December 2005. EPA uses a process known as risk assessment to
estimate the health risk from exposure to these substances,
collectively referred to in this report as contaminants.[Footnote 1]
While highly technical by nature, risk assessments, along with other
relevant information, serve as a basis for regulatory decisions that
protect human health. EPA's risk assessments are shaped by available
scientific information and by provisions in major environmental
statutes, such as the Clean Air Act, and they affect a range of
stakeholders, including regulated industries, federal agencies,
environmental advocacy groups, academic and other researchers, and the
public.[Footnote 2]
In 1994, as part of a congressionally mandated review of the methods
used by EPA to estimate the risk of developing cancer from exposure to
hazardous air pollutants, the National Academy of Sciences (NAS) issued
a report entitled Science and Judgment in Risk Assessment. This report
focused primarily on hazardous air pollutants and provided an overview
assessment of EPA's risk assessment methods.[Footnote 3] In providing
this overview, the NAS committee identified several themes, largely
focusing on the quality and availability of essential information, that
serve as a useful framework for discussing the risk assessment process:
* Implementation. EPA faces certain overarching, institutional issues
that affect its implementation of the risk assessment process.
* Data needs. Data necessary to complete scientifically plausible risk
assessments are often unavailable on such topics as the actual levels
of exposure to contaminants and how those exposures affect human
health.
* Default options. In the absence of convincing scientific knowledge or
data, EPA relies on assumptions, often conservative in nature, about
such questions as how exposure to low doses of a contaminant affects
human health.
* Method and model evaluation. The predictive accuracy of methods and
models, such as those used to predict how a contaminant will be
processed once it enters the body, is not always known.
* Uncertainty. The lack of precise knowledge about the type,
likelihood, and extent of adverse effects from exposure to a
contaminant results in uncertainty in risk assessment that can be
reduced only by advances in scientific understanding or the collection
of better data.
* Variability. Variability, in exposure or in the biological
differences among humans that determine how exposure to contaminants
affects health, can be better characterized with more data but cannot
be reduced or eliminated.
* Aggregate and cumulative effects. Aggregate effects are the results
from exposure to a single contaminant by any combination of means--
including inhalation, contact with the skin, and ingestion; cumulative
effects are the results from exposure to multiple contaminants by any
combination of means.
Science and Judgment in Risk Assessment was one of several reports by
NAS that discussed risk assessment in general and made recommendations
for ways to improve it.[Footnote 4] In addition, the Presidential/
Congressional Commission on Risk Assessment and Risk Management issued
a report in 1997 that reviewed risk assessment, as well as risk
management, in regulatory programs.[Footnote 5] Furthermore, the Office
of Management and Budget (OMB) issued guidance related to peer review
and ensuring the quality, objectivity, utility, and integrity of
information released to the public.[Footnote 6] More recently, in
January 2006, OMB issued a proposed bulletin that advocates minimum
standards for the scientific quality of risk assessments to enhance
their technical quality and objectivity.
In the context of these prior reviews, you asked us to (1) identify the
significant recommendations to improve human health risk assessment
that have been made since 1994; (2) describe what EPA has done to
modify its human health risk assessment process over the same period;
(3) determine the effects these past modifications have had on the
preparation of risk assessments; and (4) identify any additional
actions experts believe EPA could take to improve its risk assessment
process in the future, and the barriers EPA would face in doing so.
To identify significant recommendations to improve human health risk
assessment since 1994, we reviewed EPA documents, including those
produced by EPA's Risk Assessment Forum, Science Policy Council,
Council for Regulatory Environmental Modeling, and Science Advisory
Board, as well as each of EPA's program offices. We also reviewed our
own reports and documents produced by NAS and the Presidential/
Congressional Commission on Risk Assessment and Risk Management. We
also spoke with experts in the risk assessment field, who identified
many of these documents in the course of our discussions and provided
insight into some of the recommendations made therein. To describe what
EPA has done to modify its human health risk assessment process, we
interviewed program office managers from EPA's Office of Air and
Radiation, Office of Pesticide Programs, Office of Pollution Prevention
and Toxics, Office of Water, and Office of Research and Development
(ORD). While we recognize that EPA's regional offices and the Office of
Solid Waste and Emergency Response conduct risk assessments, for the
most part their work focuses on site-specific assessments and thus was
not included in this effort. Within ORD, we interviewed managers in two
of EPA's laboratories (the National Health and Environmental Effects
Laboratory and the National Exposure Research Laboratory) and three of
EPA's research centers (the National Center for Environmental
Assessment, National Center for Environmental Research, and National
Center for Computational Toxicology). Furthermore, we attended various
EPA and stakeholder group training sessions and meetings.
To determine the effects these modifications have had on the
preparation of risk assessments, we surveyed risk assessors from the
program offices mentioned above. We sought their views on the
usefulness of many of these modifications, as well as on aspects of
EPA's risk assessment process, including guidance documents, training,
organizational structure, and collaboration. The survey and results can
be viewed at [Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-06-
637SP]. In addition, we interviewed experts in the risk assessment
field and obtained their perspectives on the extent to which these
modifications were helpful to EPA's risk assessment process. To
identify additional actions experts believe EPA could take to improve
its process and to identify barriers to such actions, we contacted
experts representing a range of stakeholders in the process.
Specifically, we contacted risk assessment scientists; toxicologists;
scientific advisers to EPA; state officials; and representatives from
regulated industries, government agencies, and environmental advocacy
groups who have an expertise in risk assessment. We used an iterative
process (often referred to as the "snowball sampling" technique) to
identify these knowledgeable experts and selected for interviews those
who would provide us with a broad and balanced range of perspectives on
EPA risk assessment practices. We used a standard set of questions to
interview each of these experts to ensure we consistently discussed
each aspect of EPA risk assessment policies and practices. (See app. I
for a more detailed description of the methodology we employed.) In
addition, we consulted with NAS's Board on Environmental Studies and
Toxicology at its June 2005 meeting to obtain input on the areas in
which EPA has made the most progress in improving its risk assessment
practices and areas EPA will need to focus on in the future. We used
the experts present at this meeting as a starting point for our
snowball sampling technique used to identify subsequent experts. We
conducted our work from February 2005 through March 2006 in accordance
with generally accepted government auditing standards.
Results in Brief:
Independent reviewers, including NAS, have made a number of significant
recommendations to improve EPA's human health risk assessment process
since 1994 that can be grouped and discussed in terms of the seven
themes originally identified by NAS in 1994. First, reviewers have said
that EPA should improve its overall implementation of the process with
such steps as more thorough planning of its risk assessments and
greater use of independent reviews by scientists (called peer reviews).
Second, to improve the quantity and quality of the data upon which risk
assessments are based, reviewers have recommended that EPA better
utilize the scientific data it has and identify additional data needs
on the potential adverse effects from exposure to contaminants, and
prioritize and support research to meet the data needs identified.
Third, because EPA lacks data to fully assess the health risk from
exposures, reviewers have recommended that when the agency relies on
assumptions--known as default options--it should, among other things,
more clearly indicate when it relies on default options and how it
chooses them. Fourth, to improve the accuracy of EPA's risk
assessments, reviewers have stated that EPA should better evaluate the
methods and models used in its analysis and incorporate newer, more
powerful tools when appropriate. Fifth, to address the inevitable
uncertainties associated with gaps in scientific knowledge and general
unknowns about model and data accuracy, EPA should, according to
reviewers, more explicitly analyze and characterize the sources of
uncertainty in its risk assessments and, when possible, discuss the
uncertainties both descriptively (qualitatively) and numerically
(quantitatively). Sixth, reviewers have also recommended that EPA
enhance its analysis of variability in levels of exposures to
contaminants, as well as differences in individual reactions to
exposure. Finally, because people are typically exposed to a mixture of
contaminants through a variety of means, such as contact with skin and
breathing air, reviewers have recommended that EPA improve how it
considers the effects of combinations of contaminants and all possible
means of exposure.
EPA has strengthened many aspects of its risk assessment process since
1994, and improvement efforts are ongoing. First, EPA has improved
implementation of its risk assessment process by, for example,
beginning to improve risk assessment planning and creating scientific
leadership positions, such as the Office of the Science Advisor.
Second, EPA has initiated actions to develop missing or incomplete
scientific data on the potential adverse effects from exposure to
contaminants. For example, EPA officials told us they have begun to use
the planning and review processes to determine what data are needed and
communicate these needs to both EPA and outside researchers. Third, EPA
has cited the need for risk assessments to be more transparent about
their use of default options. For example, EPA has recently issued
guidance describing default options that are appropriate for certain
purposes and directing risk assessments to disclose the default options
used in a particular risk assessment. Fourth, EPA is enhancing its use
of models and embracing new methodologies. For example, EPA has
established a group--the Council for Environmental Regulatory Modeling-
-to review models and provide guidance in model selection. Furthermore,
some program offices now use more advanced models to predict how a
contaminant will be processed once it enters the body. Fifth, EPA
generally characterizes uncertainty descriptively, but has begun to
incorporate quantitative techniques into its uncertainty analyses. For
example, EPA typically uses a tiered approach to conducting uncertainty
analysis, starting as simply as possible, describing uncertainty
qualitatively, and sequentially employing more sophisticated analysis,
such as probabilistic analysis, as warranted. Sixth, EPA has made
progress in describing variability due to differences in both the
exposure and the susceptibility of exposed individuals to contaminants.
For example, when determining a level of exposure that is unlikely to
be harmful, EPA includes adverse effects for people who might be at
increased risk because of their age or the state of their health.
Finally, EPA has begun to take steps to consider the combined effects
of exposure to multiple contaminants through multiple means of
exposure. For example, EPA has developed a framework to assess the
combined, or cumulative, risk and has directed its program offices to
include cumulative risks when planning major risk assessments.
EPA risk assessors believe the modifications EPA has made over the past
10 years--particularly issuing additional guidance--have generally
helped them improve risk assessments, but collaboration and training
could be improved. Most EPA risk assessors believe that agencywide
guidelines and policy and reference documents have helped them prepare
risk assessments by, for example, providing useful frameworks for
evaluating potential harm from chemicals, and have resulted in greater
consistency among risk assessments prepared by different offices within
EPA. Furthermore, EPA's collaboration with external researchers,
including other federal research entities, academia, and industry, has
improved EPA's ability to conduct risk assessments by providing
expertise and research not always available within the agency,
according to risk assessors. In addition, risk assessors reported that
internal collaboration among EPA offices is moderately to very
effective, but could be improved. For example, a few risk assessors
commented that the program offices' knowledge of the regulatory context
in which research will be used helps the researchers structure their
work. However, risk assessors also reported that collaboration is
hindered within EPA by, for example, conflicting priorities among the
various offices and the poor communication between some of them.
Finally, while risk assessors said improved training has also helped
them gain relevant skills and knowledge, over 70 percent of the risk
assessors responding to our survey stated that more in-depth or
relevant training would improve their ability to prepare risk
assessments. In addition, they believe training for risk assessors and
managers in specific technical and scientific areas, such as emerging
scientific issues and the use of newer models, is lacking.
While the experts we spoke with said the modifications EPA has made
over the past 10 years have been beneficial overall, they identified
additional actions EPA could take to improve its risk assessment
process, recognizing that EPA may face barriers to doing so.
Specifically, experts said EPA could improve the planning it undertakes
prior to starting a risk assessment by better focusing on what data are
needed for the assessment and by involving stakeholders early in this
planning process. For example, several experts said that increased
involvement with a broad range of stakeholders early in the planning
process would help identify alternative methods and models and obtain
stakeholder concurrence with the agency's approach. In addition,
experts said EPA could more thoroughly evaluate methods and models,
transparently document its analytic choices, and enhance internal
review. For example, several experts said that EPA should more
transparently communicate which default assumptions were used in risk
assessments, why the defaults were chosen, and what judgments EPA was
making when it employed certain methods. Finally, experts said EPA
could provide additional training for risk assessors, managers, and
stakeholders on all elements of the risk assessment process, such as
how to use and apply models and how to interpret data from emerging
scientific fields. While these efforts would further improve the risk
assessment process, experts pointed out inherent barriers that EPA may
face in carrying them out, such as the scientific complexity of risk
assessment, the difficulty of obtaining and applying data, and a
cultural resistance to deviating from established methods. For example,
several experts said that EPA's risk assessments have grown more
technically challenging and require risk assessors and managers to have
different skills from what they had in the past.
To further improve the risk assessment process, GAO recommends that EPA
enhance early planning of each risk assessment, identify and
communicate data needs to the research community, and support
development and implementation of in-depth training for risk assessors
and managers.
We provided EPA with a draft of this report for review and comment. EPA
neither agreed nor disagreed with our findings and recommendations.
However, the agency provided specific comments to improve the report's
technical accuracy, which we incorporated as appropriate.
Background:
Risk assessment, as used in public health and environmental settings,
is inherently a complex and highly technical process that provides a
systematic scientific description of potential adverse effects from
exposure to contaminants. Risk assessments are conducted to estimate
whether and how much harm can be expected from exposure to a given
contaminant or mixture of contaminants and to help determine whether
the harm is significant enough to require regulatory or other
corrective action. The adverse effects from exposure can be acute, such
as respiratory illnesses or poisonings, or chronic, such as cancer or
reproductive or genetic abnormalities. The result of a risk assessment
is a statement of the likelihood that an exposed population will be
harmed and to what extent. EPA's human health risk assessment process
generally consists of the four stages recommended in 1983 by the
National Academy of Sciences (NAS): (1) hazard identification
(determining whether a substance could cause adverse affects and what
those adverse affects would be), (2) dose-response assessment
(determining the relationship between the magnitude of exposure to a
contaminant and the probability and severity of adverse effects), (3)
exposure assessment (identifying the extent to which exposure is
predicted to occur), and (4) risk characterization (combining the
information from the preceding analyses into a conclusion about the
nature and magnitude of risk).
Risk assessment plays a critical role in EPA's regulatory decisions,
but the characterization of risk that results from a risk assessment is
only one piece of information used to inform decisions on regulatory
standards for protecting human health. This analysis is integrated with
other information, such as economic information on the costs and
benefits of mitigating the risk, technological information on the
feasibility of managing the risk, and the concerns of various
stakeholders. The combined analysis informs agency officials who
ultimately make regulatory decisions. This overall process is generally
called risk management. (See fig. 1.) According to NAS, the risk
assessment process should be conceptually distinguished from how the
results of that process are used in the risk management process.
However, in practice, maintaining this separation is difficult because
the two processes are fundamentally linked by the complementary needs
of the risk assessors and the risk managers. Specifically, risk
assessors need to be aware of the context in which the assessment will
be used and to communicate their key findings, as well as their
confidence in them, in a way that risk managers can understand and
apply. Risk managers need to ensure that the risk assessment has been
properly performed and can be integrated with other information to make
and justify a sound regulatory decision.
Figure 1: Typical Sequence of Risk Assessment and Risk Management
Processes:
[See PDF for image]
Source: EPA.
[End of figure]
EPA's human health risk assessment process is limited to a great extent
by the amount of scientific data available on contaminants and by the
level of scientific understanding about how contaminants act in the
body to produce adverse effects. Data are often unavailable, and
science cannot always provide definitive answers. The complex and
sophisticated analytic tools used in risk assessment cannot overcome
basic scientific unknowns. As a result, EPA's risk assessments almost
always include assumptions about potential adverse effects. Some
assumptions are conservative--that is, they are intended to help ensure
that the agency does not underestimate health risks. Some critics of
EPA's risk assessment practices believe EPA uses assumptions that are
unjustifiably conservative, given new scientific data and methods, and
thereby produces estimates that overstate actual risks. Other
stakeholders, however, criticize some agency assumptions for not being
conservative enough in the face of scientific uncertainties. These
criticisms often result in legal challenges to EPA's decisions.
EPA's human health risk assessment process is also greatly dependent on
its degree of knowledge about the population's level of exposure to
contaminants. This knowledge includes the extent to which people are
exposed to potentially harmful contaminants in their daily lives, the
chemicals to which they are most often exposed, the levels of such
exposures, how exposures change over time, and the sources of exposure.
Risk assessors, researchers, and policymakers must often rely on
estimates of human exposure that are often derived from data showing
the extent the chemicals are found in the air, water, food, or other
environmental media and assumptions about how and at what rate the body
absorbs the chemicals it contacts. In addition to estimates from
models, extrapolations from experiments involving animals, and
measurements of chemicals in the environment, EPA also relies on more
direct methods to measure exposure and more accurately assess exactly
how much of a contaminant has been absorbed in the body. For example,
EPA uses population activity models--models based on actual human
behavior, such as the time spent outdoors or, for children, the amount
of time spent on the floor--to better estimate an individual's true
exposure.
Risk assessment activities at EPA are carried out by both the agency's
Office of Research and Development (ORD)--its principal scientific and
research arm--and its program and regional offices, including the
Office of Air and Radiation, Office of Pesticide Programs, Office of
Pollution Prevention and Toxics, Office of Solid Waste and Emergency
Response, and Office of Water. ORD carries out all steps of highly
complex, precedent-setting risk assessments for specific contaminants,
such as dioxin. In addition, ORD often has responsibility for the first
two steps of the risk assessment process--hazard identification and
dose-response assessment--in support of the program offices. In such
cases, the last two steps--exposure assessment and risk
characterization--are the responsibility of the various program
offices. Three notable exceptions exist to this division of
responsibility. The Office of Pesticide Programs and the Office of
Pollution Prevention and Toxics often conduct all steps of risk
assessments independently, in part, because the relevant statutes for
these program offices place strict time frames on decision making and
the confidential nature of data provided to the agency under these
programs. Furthermore, the Office of Water also does all of the stages
for some of the assessments for purposes of the Safe Drinking Water
Act.
EPA's approach to risk assessment varies across program offices, often
as a result of different regulatory and legal requirements. For
example, a branch of the Office of Pollution Prevention and Toxics
assesses data submitted by industry applicants on approximately 2000
new chemicals annually under the Toxic Substances Control Act (TSCA) of
1976. TSCA generally requires EPA to evaluate the chemicals within 90
days, but does not require all applicants to conduct laboratory tests
on the potential hazards and risks of the chemicals. In contrast, the
Clean Air Act requires EPA to establish National Ambient Air Quality
Standards, to review the scientific basis for those standards at least
every five years, and to revise the standards as appropriate. As part
of this process, ORD summarizes the most current scientific information
on the pollutant in question. ORD's findings and conclusions are then
combined with other exposure and risk analyses to determine what, if
any, revisions should be made to the standards.
Risk assessment has been the center of numerous reports, analyses, and
regulations over the years. One of the earliest was the National
Academy of Sciences' 1983 report Risk Assessment in the Federal
Government: Managing the Process, often referred to as the "Red Book"
because of the color of its cover. Subsequently, NAS released several
related reports, including Science and Judgment in Risk Assessment
(1994), Understanding Risk: Informing Decisions in a Democratic Society
(1996), and Strengthening Science at the U.S. Environmental Protection
Agency (2000). In addition, Congress, via the Clean Air Act Amendments
of 1990, created the Presidential/Congressional Commission on Risk
Assessment and Risk Management (Commission) and required it to
investigate the policy implications and appropriate uses of risk
assessment and risk management in various regulatory programs designed
to protect people from cancer and other chronic health effects that may
result from exposure to hazardous substances. The Commission published
its two-volume final report in 1997.
In addition, the Office of Management and Budget (OMB) has issued
guidelines, reports, and bulletins that have affected the practice of
risk assessment. For example, in October 2001, OMB issued its
Guidelines for Ensuring and Maximizing the Quality, Objectivity,
Utility, and Integrity of Information Disseminated by Federal Agencies,
which required agencies to issue their own guidelines to ensure the
quality of information being disseminated. Furthermore, in September
2003, OMB issued a report to Congress on the costs and benefits of
federal regulation. As part of this effort, OMB sought public comment
on the practice of risk assessment, many of which were directed at, and
passed along to, EPA. OMB also issued the Final Information Quality
Bulletin for Peer Review in December 2004 that provided guidance to
federal agencies on what information is subject to peer review and
defined a planning process for peer review. Most recently, on January
9, 2006, OMB released a draft bulletin on procedures agencies should
use to conduct risk assessments and information that should be
included. Public comment on this draft will be accepted until June 15,
2006.
Independent Reviewers Have Recommended Improvements to EPA's Risk
Assessment Process Since 1994:
Independent reviewers, including the National Academy of Sciences (NAS)
and the Presidential/Congressional Commission on Risk Assessment and
Risk Management have made a number of significant recommendations to
improve EPA's human health risk assessment process since 1994. These
recommendations cover a range of actions, including improving planning
of what will be required to complete a particular risk assessment and
what key stakeholders need to be involved, supporting development of
new scientific data on the potential adverse effects from exposure to
the contaminant under review, and enhancing analysis of the potential
risk and its uncertainties. All of them can be summarized and discussed
in terms of the seven themes--implementation, data needs, default
options, method and model evaluation, uncertainty, variability, and
exposure to multiple contaminants and routes of exposure--reported in
NAS's report Science and Judgment in Risk Assessment.[Footnote 7]
Improve Planning and Review Process and Ensure an Appropriately Skilled
Workforce to Conduct Risk Assessment:
Independent reviewers made a number of recommendations to EPA to
improve the overall implementation of its risk assessment process. The
reviewers recommended that EPA improve its planning of risk assessments
before beginning the process and adopt an iterative risk assessment
approach. Reviewers also stressed that EPA should increase its use of
risk assessment reviews by independent scientists, known as peer
reviews; increase stakeholder involvement in the risk assessment
process; and ensure it has the workforce needed to conduct quality risk
assessments. Finally, the reviewers recommended that EPA improve the
way it characterizes the risk it finds and strengthen the link between
risk assessment and risk management.
Improve Planning and Adopt an Iterative Risk Assessment Approach:
In 1996, NAS reviewers stressed the importance of planning from the
beginning of a risk assessment to incorporate the perspectives and
knowledge of interested and affected parties.[Footnote 8] Because of
the large number of stakeholders interested in the results of a risk
assessment, it is important to ensure that the risk assessment
addresses all of the stakeholders' needs. NAS pointed out that one way
to do this is to be aware of the stakeholders' concerns from the outset
and incorporate them into the analysis and characterization of risk. By
involving stakeholders early, risk assessors can ensure that they ask
the right questions, make appropriate assumptions, and determine the
best way to summarize information, thereby potentially making the
resulting message more credible to these parties.
In addition to improved planning, NAS suggested in 1994, and the
Commission concurred, that EPA develop the ability to conduct risk
assessments iteratively--that is, begin with a screening analysis to
ascertain the potential risk and refine that analysis as appropriate.
Such an approach would start with relatively inexpensive screening
techniques and move to more resource-intensive data gathering and
modeling as the particular situation warranted. To guard against the
possibility of underestimating risk, these screening techniques should
be constructed to err on the side of caution where there is
uncertainty.
Increase Peer Review and Stakeholder Involvement in the Risk Assessment
Process:
Each of the NAS reports we reviewed, as well as the report by the
Commission, recommended ways EPA could improve its peer review process
and better involve stakeholders in risk assessment. These independent
reviewers said peer review is critical to evaluate the accuracy and
appropriateness of technical information, scientific observations, and
interpretations used in regulatory decision making. The Commission
observed that peer review can also help in the planning stages of a
risk assessment to put a problem in context and draw on the knowledge
of experienced researchers, public health officials, and scientists.
In particular, NAS recommended in 2000 that EPA change its peer review
policy to ensure greater independence of these reviews from the
control, or appearance of control, of the program managers.[Footnote 9]
EPA's Science Advisory Board had expressed concern about potential
conflicts of interest because agency policy allowed the same individual
to serve as both project manager for a particular work product and peer
review leader.[Footnote 10] The NAS committee concurred with this
concern.
In addition, NAS's 1994 report recommended that EPA collaborate more
with outside parties to improve the overall risk assessment process.
For example, EPA could use external advisory groups, such as its
Science Advisory Board, to help ensure that risk assessment decisions
use the best science and incorporate full public discussion and
participation from the scientific community. Such collaboration could
also include a process for public review and comment. The Commission
also said that agencies should use advisory groups, composed of
stakeholders, to periodically evaluate the use of technical
information. In addition, the Commission recommended that agencies
establish clear, written guidelines for peer review and match the use
of peer review to the importance of the decision to be made.
In 1996, NAS commented on the importance of stakeholder involvement in
the risk assessment process. NAS suggested that the risk assessment
process involve the spectrum of interested and affected parties,
including decision makers and specialists in risk analysis, at each
step of the process. According to NAS, such involvement will help
ensure that as much important, relevant knowledge as possible enters
the process and that the process remains open and inclusive. NAS also
mentioned another benefit of involving these stakeholders in the
process: the participation of a spectrum of people helps ensure that
the process will be framed correctly and the resulting risk
characterization will be accurate, balanced, and informative.
Ensure EPA Has the Skilled Workforce Needed to Conduct Quality Risk
Assessments:
Each of the NAS reports we reviewed contained recommendations stressing
the importance of an organization's ability to ensure that it has the
expertise and leadership needed to conduct risk analyses. In addition,
according to current workforce models, agencies need to ensure that
they have effective training and the capability to identify what skills
and competencies the employees and the organization need. In 1994, NAS
recommended that EPA acquire additional expertise, as needed, to better
interpret data and reach sound conclusions about the risks to human
health from a contaminant. For example, many of the conclusions
regarding the potential risks from a particular contaminant rely upon
risk assessment models based on animal data or, when available, human
evidence from epidemiological studies. The quality of the risk
assessment will depend upon how well these data are interpreted to
predict health effects in human populations. NAS recommended that EPA
acquire staff with specialized skills in fields such as toxicology to
successfully complete this type of analysis.
NAS also recommended in 2000 that EPA continue to place high priority
on ORD's graduate fellowship and postdoctoral program. The report
stated that to achieve scientific and technical excellence, EPA must
first attract, retain, and properly support a dedicated professional
staff. NAS also noted that while EPA has many outstanding scientists
and engineers, ORD's workforce is aging and many staff may retire in
the relatively near future. Periodic hiring freezes, combined with high
competition from the private sector, had made it difficult for ORD to
recruit the new talent needed to sustain and enhance the research
workforce. NAS concluded that ORD's graduate fellowships and
postdoctoral programs brought a stream of fresh scientific and
technical talent into EPA's research program and helped train future
researchers in environmental science, engineering, and other
disciplines. NAS urged EPA to continue to place a high priority on
these programs.
In 2000, NAS made a series of recommendations related to scientific
leadership and talent at EPA. Specifically, NAS recommended that EPA
establish a new position--deputy administrator for science and
technology--to address concerns that science at EPA was not perceived
to be strong and that many EPA scientists believed their scientific
knowledge and resources were not effectively used. Traditionally, EPA's
most senior science official had been the assistant administrator for
research and development, but that official lacked agencywide
responsibility or authority to oversee the scientific and technical
basis for regulatory and policy decision making. In addition, EPA's
program offices were not required to follow scientific advice from ORD.
Consequently, the NAS panel concluded that EPA needed an appropriately
qualified science official at a sufficiently high level with both the
authority and responsibility for agencywide scientific performance.
Improve Characterization of Risk and More Closely Link Risk Assessment
with the Needs of Risk Managers:
Finally, reviewers recommended ways EPA could improve its
characterization of risk and better link its risk assessment and risk
management processes to harmonize the scientific aspects of risk
assessment and the broader policy objectives of risk management. NAS's
1996 report, which primarily focused on risk characterization and the
role it plays in risk assessment, stressed that successful risk
characterization can result in better and more widely accepted risk
assessment and risk management decisions. The Commission echoed NAS's
position and recommended that risk characterizations should include
information useful to everyone in the risk management process, such as
information on who is at risk, how they might be affected, what the
severity of an adverse effect might be, and how confident the risk
assessors are about their predictions.
Reviewers also suggested that EPA better link its risk assessment and
risk management processes. EPA had tried to separate these processes
entirely to avoid the possible perception that EPA made scientific
judgments on the risk posed by a contaminant on the basis of its
willingness to regulate the substance rather than on the science.
However, NAS pointed out that while some degree of judgment is
necessary, the science-policy judgments EPA makes in the course of risk
assessment should more clearly be informed by the agency's risk
management priorities and goals. According to NAS, better linkage
between risk assessment and risk management will help ensure that the
risk assessments will be more accurate and relevant to risk managers.
The Commission concurred, stating that risk assessment should be guided
by an understanding of the issues important to risk managers' decisions
about how to protect public health and the environment.
Review Existing Data, Identify Data Gaps, Prioritize Research Needs,
Foster Development of New Data, and Improve Strategic Research Planning
and Collaboration:
In 1994, NAS found, in general, that EPA did not have the full range of
data needed to conduct adequate risk assessments to estimate the health
risks associated with most contaminants--for example, data related to
the effect a contaminant has on the body and the extent of exposure to
the contaminant. These data are essential to ensure the accuracy and
precision of the risk assessment. In addition, NAS recommended that EPA
increase its collaboration with researchers and improve the
transparency of its research priorities.
To help address EPA's dearth of data, NAS recommended, among other
things, that EPA review its existing databases, such as the Integrated
Risk Information System (IRIS), and identify data gaps.[Footnote 11] As
part of its database review, NAS recommended that EPA compile an
inventory of the chemical, toxicological, and epidemiological
literature in the databases to determine what gaps exist. NAS further
suggested that EPA prioritize its future research on the basis of the
significance of the missing data to risk assessments, convey its data
needs to other public and private researchers, such as the Agency for
Toxic Substances and Disease Registry,[Footnote 12] and develop
incentives to expedite the generation of needed data by these entities.
Furthermore, in 2000, NAS recommended, among other things, that EPA
expand the multiyear research planning by its Office of Research and
Development (ORD). For example, ORD had developed plans for research on
topics such as particulate matter, endocrine disruptors,[Footnote 13]
and drinking water. The NAS committee pointed out that these planning
efforts will contribute to research program continuity and the
achievement of strategic goals. In addition, NAS recommended that the
plans be both continued for problem-driven research--research targeted
at a particular environmental problem--and expanded to include core
research--broader, more generic research that will help improve current
and future understanding of a scientific issue. Research should be
balanced between these two types, since core research will help ORD
better understand and anticipate environmental risks and will enable
ORD to provide better problem-specific research and technical
assistance to the agency.
NAS has also made recommendations to EPA in the area of research
accountability. Specifically, NAS recommended that EPA improve the
documentation and transparency of the decision-making process ORD uses
to set research and technical assistance priorities and allocate funds.
For example, NAS pointed to an EPA Science Advisory Board finding that
ORD's lack of transparency in its process for setting research
priorities made it difficult to evaluate the adequacy of proposed
budgets. NAS also recommended that EPA expand on its efforts to create
an inventory of science projects and programs across EPA by documenting
and publishing a comprehensive and detailed inventory. The inventory
should include information such as goals and objectives of each
project, milestones, schedules, and staff allocations and should be
used to ensure that science activities are properly coordinated through
the agencywide science planning and budgeting process and are
appropriately peer reviewed.
Once the research strategy has been established, research
collaborations can help execute it. NAS suggested that EPA should
recognize the limits of its own research capabilities and develop a
strategy to obtain outside support in research areas where ORD is not
pre-eminent. Specifically, NAS recommended EPA enhance its research
collaborations by developing and implementing a strategy to stimulate,
acquire, and apply the results of research conducted or sponsored by
other federal agencies, state agencies, universities, and industry in
this country and abroad. NAS said such collaboration is especially
important given the budget constraints EPA and the federal government
face and the breadth of knowledge required to conduct the full range of
risk assessments. In addition, NAS recommended that EPA develop
additional mechanisms to promote and facilitate research interactions
among grantees in EPA's Science to Achieve Results (STAR) grant program
and ORD research staff.[Footnote 14] For example, NAS suggested that
grant applicants could identify in their proposals how their research
might complement or supplement ongoing or planned research in the ORD
laboratories. NAS also recommended that EPA increase its efforts to
disseminate ORD's research products, explain their significance, and
assist others inside and outside the agency in applying the research.
NAS noted that while EPA's policy and regulatory work receives a great
deal of public attention, the agency's science research typically
receives a similar degree of attention only when the scientific basis
for a decision is questioned. They also pointed out that even internal
EPA offices may be unaware of important benefits from ORD's research
program.
More Clearly Indicate Use of Default Options and How They Were Chosen:
When EPA needs to rely on assumptions--known as default options--
because it lacks data to fully assess the potential health risks from
exposure to a contaminant, reviewers said EPA should, among other
things, more clearly indicate that it relied on these defaults and how
they were chosen. EPA's defaults, which are based on general scientific
knowledge and policy judgment, are, for the most part,
conservative.[Footnote 15] One example of a commonly used default
option is that laboratory animals are a surrogate for humans in
assessing health risks: An adverse effect in the animals is taken as
evidence of a chemical's potential to harm humans.
Independent reviewers agreed with EPA's use of default options as a
reasonable way to cope with the lack of available data. However, NAS
recommended that EPA be clearer about the scientific and policy basis
for each default option and when it uses a default. Furthermore,
reviewers said that EPA should fully explain under what conditions they
would depart from these default options. According to NAS, giving
greater formality to the criteria for a departure would result in
greater guidance for the public and lessen the possibility of
undocumented departures that would undercut the scientific credibility
of a risk assessment. The Commission concurred, stressing that the
defaults used in risk assessments and the uncertainty associated with
their results should be clearly identified and justified.
Better Evaluate Available Methods and Models and Incorporate More
Advanced Tools When Appropriate:
The overall accuracy of a risk assessment largely depends on the
validity of the various analytic methods and models EPA uses to assess
the toxicity of, and exposure to, a particular contaminant. However,
according to NAS, EPA often does not clearly understand the extent to
which the methods or models it chooses accurately predict the toxicity
or exposure to a contaminant. For example, because of limited
scientific information on how contaminants actually work in the body to
produce adverse effects in humans, EPA frequently uses a method that
relies on studies involving laboratory animals to understand the
toxicity of a substance. The concentrations of the contaminant
introduced into the animals as part of these studies are higher and
administered for shorter periods of time than humans would normally
experience. Consequently, to determine the expected response in people,
EPA extrapolates the response from laboratory animals to humans. While
such extrapolations are useful to predict potential harmful effects of
a contaminant, different analytic methods may better predict the
effect.
In 1994, NAS recommended, among other things, that EPA evaluate the
accuracy of its methods and models for assessing toxicity and, when
appropriate, incorporate more advanced tools. For example, models that
are based on the underlying mechanisms at the cellular or molecular
level can more accurately estimate the dose of the contaminant that
would have an adverse biological effect on a specific part of the body.
Regarding the risk of cancer from a particular contaminant, NAS
recommended that EPA continue to both use methods involving animal
studies to evaluate the possibility of adverse effects in humans and
explore, when appropriate, mechanistic models. Furthermore, to better
convey the cancer risk associated with a particular substance, NAS
recommended that EPA develop a classification scheme that provides
narrative statements regarding the hazards posed by carcinogens and a
descriptive evaluation of the strength and nature of the evidence used
to estimate the substance's potential for causing cancer.
Regarding exposure, NAS noted that EPA had traditionally characterized
exposure according to two criteria: exposure of the total population
and exposure of a specified highly exposed subpopulation. While these
two criteria can help assess whether any particular exposure might
occur above a regulatory threshold, only considering the highly exposed
subpopulation is likely to overestimate the exposures of most of the
population. Consequently, NAS recommended, and the Commission
concurred, that EPA consider the entire range of a population's
exposure, rather than just the exposures of a highly exposed
subpopulation. The Commission also recommended that EPA identify and
evaluate highly exposed populations separately. Moreover, NAS
recommended that EPA use population-activity models--models based on
actual human activity patterns--to better estimate an individual's true
exposure and expand efforts to use personal monitoring data to better
understand actual exposures and variances across the population.
More Explicitly Analyze and Characterize the Sources of Uncertainty in
Risk Assessments:
To address the inevitable uncertainties associated with gaps in
scientific knowledge and general unknowns about model and data
accuracy, reviewers recommended that EPA more explicitly analyze and
characterize the sources of uncertainty in its risk assessments.
Numerous gaps in scientific knowledge exist regarding the health
effects of various contaminants, such as the exact amount of exposure
to a particular contaminant that can cause an adverse effect or the
biological effect of a contaminant on the body. In addition, knowledge
is often lacking about which model or method might be most appropriate
to estimate risks to human health from a particular contaminant. NAS
recommended that EPA develop guidelines for how to analyze and report
the different types of uncertainty, both for the overall assessment and
for the different stages of the risk assessment, such as hazard
identification and exposure assessment. For example, during hazard
identification, uncertainty can be related to the quality, type, and
results of scientific studies; however, during exposure assessment,
uncertainty can be related to model choice or available data.
NAS also recommended in 1994 that EPA conduct uncertainty analysis of
the risk estimate and present the identified uncertainties as
explicitly, accurately, and fully as feasible. Analysis of the effects
of uncertainties can help inform EPA decision makers and the public
about the extent of uncertainty associated with the risk assessment.
The analysis can also show where additional research might resolve
major uncertainties and where it might not. NAS recommended that the
uncertainty analysis be presented both descriptively (qualitatively)
and, where possible, numerically (quantitatively). For example, some
sources of uncertainty, such as those related to estimating exposures,
can be reduced through the use of more advanced statistical methods.
Other types of uncertainty, such as those associated with extrapolating
data from animal testing to predict the effect on humans, are more
difficult to quantify. The Commission concurred and recommended that
risk characterizations include narrative descriptions of the primary
reasons for uncertainty, as this information is likely to be more
understandable and useful than quantitative estimates or model results.
Enhance Analysis of Variability in Exposure Levels and Health Risks to
Exposed Individuals:
Variability, which refers to the natural diversity in a population, can
be better understood or described, but not reduced. To address the two
main categories of variability--one related to differences in levels of
individual exposures to contaminants and the other related to
differences in individual reactions to exposure--reviewers recommended
that EPA enhance its analysis of both types and carefully state in each
risk assessment what assumptions it made about what is and is not
accounted for. Specifically, variability related to different exposures
depends on the various concentrations of a contaminant as it disperses
in the environment, different breathing rates, and different food
consumption and personal activity patterns. For example, infants and
children generally consume more fruits, vegetables, and fruit juices
per body weight than adults, and some people, such as agricultural
workers, are more exposed to pesticides through breathing and skin
contact. The Commission recommended that risk assessments identify
groups of people who are likely to have higher exposures to
contaminants and consult these groups in the early stages of an
assessment to obtain information about all known sources of exposure.
Reviewers also recommended that EPA revise the way it estimates how
long a person is exposed to a contaminant. NAS and the Commission
recommended that EPA move away from estimates of exposure based on a
hypothetical "maximally exposed individual," who was assumed to be the
person at greatest risk in a worst-case scenario, because these
estimates do not account for a number of other factors that may affect
exposure patterns and rates, such as the time the person spends indoors
or going to work. Furthermore, estimates based on the hypothetical
maximally exposed individual likely overestimate the exposures of most
of the population and underestimate the exposures of subpopulations,
such as agricultural workers, who may be more highly exposed than the
general population. While EPA's 1992 exposure assessment guidelines
suggest the use of ranges and high-end exposure estimates chosen from
the high end of those ranges, according to NAS, EPA had not
sufficiently documented the reliability of such estimates when data are
limited.
The second type of variability--differences in human susceptibility--is
related to inherent differences among people, such as age, physiologic
characteristics, lifestyle, genetics, sex, and ethnicity. Reviewers
found that EPA's approach for reducing risks associated with chemical
exposures generally did not include information on differences in
individual susceptibility or encourage gathering evidence to identify
these differences. The reviewers recommended, among other things, that
EPA consider this "interindividual" variability and adopt a default
option for differences in susceptibility among humans. In addition, NAS
recommended that EPA assess risks to infants and children whenever it
appears that their risks might be greater than those of adults. For
example, the developing brains of infants and young children have an
increased susceptibility to contaminants that harm the nervous system,
such as lead. NAS specifically recommended that EPA sponsor research to
examine the causes and extent of interindividual variability in
susceptibility to cancer and the possible connection between
susceptibility and age, race, ethnicity, and sex. The Commission
generally concurred, adding that risk assessments should also identify
especially susceptible subpopulations, such as people with asthma who
may have an increased responsiveness to allergens and respiratory
irritants. The Commission also stated that, where possible, available
information about the range of the population's susceptibility should
be considered and used in place of default assumptions.
Better Consider the Human Health Effects of Exposure to Multiple
Contaminants and Routes of Exposure:
Reviewers recommended that EPA improve how it considers the effects of
combinations of contaminants (cumulative exposure) and all possible
paths of exposure to a single contaminant (aggregate exposure). People
are typically exposed to a mixture of contaminants through a variety of
pathways, such as contact with skin or eating food, each of which might
be associated with an increased probability of one or more health
effects. However, most risk assessments address a single contaminant
and often focus on a single pathway of exposure, such as inhalation. As
a result, NAS recommended that EPA should consider all possible
exposure pathways. For example, when assessing risk from mercury, EPA
should consider the risk to residents from inhaling mercury emitted
from a nearby industrial smoke stack, as well as the possibly greater
health risk of consuming mercury that has accumulated in the tissue of
fish that are caught and eaten locally after mercury from the smoke
stack was deposited into water.[Footnote 16]
When assessing the risks of exposure to chemical mixtures, most risk
assessments estimate the risks from individual contaminants, then
calculate the combined risk by simple addition. However, this method
ignores potentially synergistic interactions that may make the effects
more damaging to human health than anticipated or antagonistic
interactions that may make the effects less damaging than anticipated.
Consequently, this method could either under-or overestimate the total
risk. NAS said that simple addition of the risks from multiple
contaminants may be appropriate for screening-level risk estimates.
However if a more refined quantitative estimate is needed, EPA should
consider using statistical procedures to combine the risks from
exposures to multiple contaminants, which would help produce a more
comprehensive estimate of risk. The Commission concurred but stressed
that combining risks may not always be feasible; the risk analyses for
exposure to each contaminant may not be compatible because the risk
assessments may differ in accuracy. Further, the Commission recommended
that for risk assessments involving exposures to low concentrations of
multiple chemicals, the risks from each exposure should be added in the
absence of information on exactly how the chemicals affect the body.
However, if the multiple chemicals affect the body in different ways--
for example, if one chemical affected development while another
affected the nervous system--the impact of each chemical on the body
should be considered independently and not added together.
EPA Has Strengthened Many Facets of Its Risk Assessment Process Since
1994, and Efforts Are Ongoing:
EPA has modified its human health risk assessment process since 1994 in
several ways. First, the agency enhanced implementation of its risk
assessment process by, for example, issuing guidance and realigning
staff resources. In addition, EPA has taken steps to identify the
scientific data it has on the potential adverse effects from exposure
to various contaminants and has established collaborative relationships
with external researchers to foster the development of needed
additional data. Furthermore, EPA has begun to improve its use of
default options, enhance its modeling capabilities, and explore new
methodologies. EPA has also begun to characterize uncertainty
quantitatively and analyze and communicate variability more thoroughly.
Finally, EPA is more often considering the combined effects of exposure
to multiple contaminants through multiple pathways. Most of these
efforts are ongoing and can be discussed in terms of the themes
presented in the previous section.
EPA Has Enhanced Implementation of Key Aspects of Its Risk Assessment
Process:
EPA has taken a number of steps to improve implementation of its risk
assessment process. Specifically, EPA has developed guidance and policy
documents at the agency and program office levels; built scientific
capacity; modified components of its approach to risk assessment; and
refined its peer review and quality-assurance practices.
EPA Has Issued Many Agencywide and Program Office-Specific Guidance and
Policy Documents to Improve Risk Assessment Practices:
The guidance and policy documents EPA has issued over the past decade
were intended to help staff develop and use risk assessments and to
provide basic information to the public about EPA's risk assessment
methods. While some of these documents have remained unchanged over
time, many have been revised, or will be revised, as science,
knowledge, and analytic methods have improved. Among these documents
are the guidelines issued by EPA's Risk Assessment Forum, a committee
of senior EPA scientists established to promote agencywide consensus on
risk assessment issues, which cover such topics as
neurotoxicity,[Footnote 17] exposure assessment, and carcinogenic risk
assessment. Each of the original five guideline documents created in
1986 has been updated at least once, and some are slated to be revised
again. For example, the exposure guidelines were revised in 1992 and
revisions are currently being planned. In addition, the forum has
issued two entirely new sets of guidelines since 1994--Guidelines for
Reproductive Toxicity Risk Assessment and Guidelines for Neurotoxicity
Risk Assessment--and has developed a number of policies on, among other
things, risk characterization, peer review, and evaluating risk to
children. EPA has also issued interim policy memorandums and position
papers on scientific issues such as genomics and endocrine disruption.
Similarly, much of EPA's agencywide guidance issued since 1994 has
undergone revision and has its origins in earlier policy documents. For
example, EPA's Risk Characterization Handbook, issued in 2000, has its
roots in the 1995 Policy for Risk Characterization. The handbook
stresses that risk characterization should be transparent, clear,
consistent, and reasonable. EPA's policy on the use of peer review was
originally issued in 1994 and was followed up by issuance of peer
review handbooks in 1998 and again in 2000.[Footnote 18] The peer
review policy was recently updated in January 2006. EPA has also issued
technical guidance, such as its review of the processes to estimate a
daily or continuous exposure to humans that is likely to be without
appreciable adverse effects during a lifetime.
In addition to the EPA-wide guidance, many of the program offices have
also issued guidance documents that support their particular risk
assessment efforts. In general, the office-specific guidance documents
provide risk assessors with analytic tools and exposure scenarios
pertinent to the statutory responsibilities of the office. For example,
the Office of Pollution Prevention and Toxics created guidance in the
form of an analytic tool to screen chemicals in the absence of data,
which frequently occurs because of the lack of a requirement for
industry to develop extensive data on new chemicals or new uses of
existing chemicals. In addition, the Office of Pesticide Programs has
issued pesticide-specific guidance documents. For example, to help
ensure consistency in pesticide chemical risk assessments, the Office
of Pesticide Programs issued guidance for developing residential
exposure assessments and developed a template for making and
documenting registration eligibility decisions.
EPA Has Built Scientific Capacity through Increased Focus on Scientific
Leadership, Greater Reliance on Research Advisory Groups, and
Development of Future Scientific Talent:
EPA enhanced its scientific leadership through the creation of the
position of science advisor in 2002 and the Office of the Science
Advisor in 2003, the increased reliance on research advisory groups
composed of senior EPA scientists and external experts, and the
continuation of its research fellowship programs. The overarching
responsibility of the science advisor is to coordinate and oversee the
scientific activities of the program offices at EPA to ensure the best
use of science. The Office of the Science Advisor provides further
leadership by establishing specific mechanisms to ensure that
scientific results, combined with technical evaluation and peer review,
play a prominent role in regulatory decisions and that EPA staff
interpret and enforce regulations consistent with the science
supporting them.
In addition to enhancing its scientific leadership, EPA has also
increased its reliance on research advisory groups since 1994. The
Science Policy Council and the Risk Assessment Forum play key roles in
advancing the practice of risk assessment at EPA. The council reviews
the adequacy of existing policies, establishes science policy as
needed, and coordinates EPA efforts related to methods, modeling, risk
assessment, and environmental technology. The Science Policy Council
staff facilitate ad hoc work groups, encourage communication and
consensus building within the agency, and participate in technical work-
group activities and deliberations.
The Risk Assessment Forum is a standing committee of senior EPA
scientists established to promote agencywide consensus on difficult and
controversial risk assessment issues and to ensure that this consensus
is incorporated into guidance. According to an agency official, the
forum is designed as a venue where staff can meet and discuss common
risk assessment issues across program offices. One of the forum's main
contributions to risk assessment at EPA has been the issuance of a
series of risk assessment guidelines. The forum is currently working on
new guidelines, such as one related to adverse effects on the immune
system. When more specificity is needed on an existing guideline, the
forum issues companion pieces, known as "purple books" because of the
color of their cover, that provide additional or updated information.
The Board of Scientific Counselors (BOSC) provides objective and
independent advice, information, and recommendations about ORD's
research program to ORD's assistant administrator. BOSC is composed of
scientists and engineers from academia, industry, and environmental
organizations who are recognized as experts in their fields. In 1998,
BOSC completed a peer review of ORD's laboratories and
centers.[Footnote 19] BOSC completed a second review of the
laboratories and centers in 2002 and 2003 that identified key
accomplishments of the laboratories and centers, as well as areas for
future improvement. In addition, after EPA's Office of the Science
Advisor issued its 2004 staff paper,[Footnote 20] it asked BOSC to host
a workshop for EPA staff and other interested stakeholders, such as
industry, environmental groups, and researchers, to provide feedback to
refine EPA's current practices and to suggest alternative approaches
for specific aspects of risk assessment.
EPA has also worked to foster scientific excellence and enhance the
skills of its existing workforce through its graduate and postdoctoral
fellowship programs. One such program, the EPA/ORD Postdoctoral
Fellowship Program, began in 1998, and, as of May 2003, 205 individuals
had participated in the program. One benefit of the program is that it
helps provide a ready pool of talented candidates for EPA vacancies. In
fact, according to a study of the program conducted by the National
Council for Science and the Environment, nearly half of the former
postdoctoral participants had taken permanent positions at EPA. The
Science to Achieve Results (STAR) fellowship program is designed to
encourage masters and doctoral students to pursue careers in an
environmental field. The STAR fellowship program has provided new
environmental research in the biological and health sciences, two
fields related to the development of human health risk assessment. EPA
has also partnered with the Association of Schools of Public Health
(ASPH) to offer 1-year placements of graduates in EPA laboratories,
centers, and program offices to work on public health issues. In the
announcement of opportunities for the 2006 ASPH Fellows Program, a
dozen fellowships are being offered in areas related to human health
risk assessment. For example, the National Center for Environmental
Assessment is offering a fellowship to develop health assessments for
various chemicals, and the National Center for Environmental Research
is offering a position for someone interested in working on developing
models or analyzing uncertainty in risk assessments.
EPA Has Begun to Incorporate Planning Activities and Stakeholder Input
into Its Risk Assessment Approach:
To improve planning, which is a part of all risk assessments to some
degree, EPA has issued various guidance documents and held workshops
for staff. One of EPA's earliest related guidance documents,[Footnote
21] released in 1997, was designed to help risk assessors and risk
managers plan and document the scope of risk assessments and to
consider input from appropriate stakeholders and experts, especially in
those assessments involving the effects of combinations of
contaminants.[Footnote 22] EPA followed up this guidance with workshops
to help staff apply it in risk assessments. In January 2002, EPA issued
a handbook to reflect some of the lessons learned from implementation
of the 1997 guidance to make risk assessments more useful to decision
makers and other stakeholders. These lessons, conveyed through case
studies, include that planning can be particularly valuable when the
assessment is complex, controversial, or precedent setting, and that
explaining uncertainty to stakeholders can help develop trust,
credibility, and support for the decision-making process.
The 2000 Risk Characterization Handbook also strongly advocates the use
of planning and presents a number of topics for both risk managers and
risk assessors to consider, such as identifying the stakeholders in the
process; scope of the effort; relevant management goals, issues, and
policies; available data; and data needs. For example, during planning,
risk assessors, risk managers, and stakeholders need to identify the
key data gaps and discuss how best to fill them, such as whether to use
existing data or conduct additional short-or long-term tests to
evaluate exposure and effects. The Office of Air and Radiation
recognized the need for planning and developed planning guidance as
part of its Air Toxics Risk Assessment Reference Library, issued in
2004. EPA acknowledged in its 2004 staff paper that it needs to
continue to stress the importance of concerted and conscious planning
with risk assessors and risk managers before a risk assessment is
started. According to EPA, risk assessors need to outline early in the
development of a risk assessment what will and will not be addressed
and how they will develop the risk assessment.
Stakeholders and the public play a key role in the planning, as well as
at later stages in the development of a risk assessment. Stakeholders,
at various levels and in various forms, can help ensure better
understanding of the risk assessment results and may promote support
for the selected risk reduction strategies. Program offices involve
stakeholders in various ways. For example, the branch of the Office of
Air Quality Planning and Standards (OAQPS) responsible for setting
certain air quality standards for six principal pollutants solicits
input from stakeholders in the planning phase of its periodic updates
to the standards it sets.[Footnote 23] In addition, the public may
officially comment on draft air quality standards once they are
publicly released. The Office of Water pursues stakeholder and public
involvement that includes working with the environmental community,
industry, trade associations, risk assessor organizations, states, and
bordering countries. In addition, the office's periodic reviews of
water quality standards and other nonregulatory actions, such as health
advisories, are all open processes that allow for public input on
various stages of the analysis.
For risk assessments involving the reregistration of pesticides, the
Office of Pesticide Programs (OPP) established a process that provides
several opportunities for public participation.[Footnote 24] Depending
on the potential health risks posed by a pesticide product, the public
has anywhere from one to four separate opportunities to comment. For
example, if risk assessors estimate that the product poses little risk
to human health, the public will have one opportunity to comment before
OPP decides whether to approve the pesticide product. For higher-risk
products, the public will have as many as four opportunities to
comment. The first opportunity to comment occurs after OPP has
completed a preliminary risk assessment. This preliminary assessment
contains all of the elements of a risk assessment and has undergone
internal review, but is not yet finalized. Notice of the opportunity to
comment is distributed to people who have elected to sign up for such
notifications, as well as through a "notice of availability" published
in the Federal Register. The public can also comment on risk
assessments prepared by the Office of Pesticide Programs through the
office's Science Advisory Panel--which holds periodic public meetings
on pesticide-related risk assessment issues, such as methods to assess
skin sensitivity to exposure to pesticides or models used to estimate
dietary exposures.
EPA has also adopted an iterative approach to many of its risk
assessments. An iterative approach begins with a screening assessment
and progressively grows in depth and scope in relation to the estimated
risks to human health. When a screening assessment identifies a
potential for a nontrivial risk, EPA decides if pursuing that risk is
appropriate based on its current priorities and available resources. If
EPA decides to pursue the risk, a more detailed, refined risk
assessment is performed. The degree of refinement is based on the type
of decision, the available resources, and the needs of the risk
manager. After refinement of the estimate, EPA reviews it to see if it
will be sufficient to answer the questions posed. Refinements proceed
iteratively until the assessment provides an adequate answer for the
decision maker within the resources available. Both the revised cancer
guidelines and EPA's 1995 Policy for Risk Characterization support an
iterative approach to risk assessment. Some program offices have also
adopted an iterative--or tiered--approach to risk assessment. For
example, the air toxics program follows a tiered approach, beginning
with an analysis that includes few data and many conservative
assumptions. If this analysis indicates that the risk may be relatively
high, assessors pursue more intensive analysis to determine if the risk
is realistic or an artifact of the lower tier's conservative
assumptions. Despite this move toward greater use of an iterative
approach, EPA acknowledges it could be clearer about when it is taking
such an approach. For example, EPA could be more transparent about when
and why it makes a risk management decision based on a screening-level
assessment rather than a more detailed assessment.
EPA Has Refined Its Peer Review and Quality-Assurance Practices:
In the years since the issuance of Science and Judgment in Risk
Assessment, EPA has made strides to improve its peer review practices.
EPA uses peer review to help ensure the quality of its risk assessments
and keep them as objective and consistent as possible. EPA's Peer
Review Policy states that scientifically and technically based work
products related to agency decisions should be peer reviewed. In 2000,
EPA issued its revised Peer Review Handbook, an update of the original
1998 edition. In the intervening 3 years, EPA's Science Advisory Board,
EPA's Office of Inspector General, the National Research Council, and
GAO scrutinized the peer review process. In response, in part, to
recommendations made by many of these groups, EPA issued the current
edition of the handbook. Among other things, it instructs EPA to
balance peer review panels in terms of expertise and biases to help
ensure a reasonable and scientific review.
In addition to issuing the Peer Review Handbook, EPA has undertaken a
number of actions to help ensure the quality of its data and
information. In May 2000, EPA established an agencywide quality-
assurance system and issued the EPA Quality Manual for Environmental
Programs. Key components of this system include assigning a quality-
assurance manager to conduct independent oversight of data quality,
developing a management plan, and conducting an annual assessment of
the quality system. In addition, the system calls for an assessment of
the data EPA used to support agency decisions to verify that they were
of sufficient quantity and quality for their intended use. In 2002, EPA
developed its information-quality guidelines in response to those
issued by OMB, which stated that agencies must ensure the quality,
objectivity, utility, and integrity of information released to the
public.[Footnote 25] EPA's guidelines outline its policy and procedures
to ensure and maximize the quality of the information it disseminates
and describe the mechanisms by which EPA reviews information prior to
dissemination. EPA issued a complement to these guidelines in 2003 to
raise awareness among the public about EPA's ongoing interest in high-
quality data and to serve as an additional resource for staff as they
evaluate the quality and relevance of information.[Footnote 26]
EPA Has Enhanced Its Strategic Planning and Refocused Staff Resources
to Initiate Review of Existing Data and Development of Needed Data:
Since 1994, EPA has initiated a number of actions to develop missing or
incomplete scientific data on the potential adverse effects from
exposure to contaminants, including refocusing and expanding the Office
of Research and Development human health risk assessment program,
improving strategic research planning, increasing collaboration with
outside researchers, and enhancing databases.
EPA Restructured and Augmented Its Research Office:
In 1995, EPA restructured ORD to more effectively generate and gather
information needed for the risk assessment process, combining 12
existing laboratories into 3 national laboratories and 2 national
centers--the National Health and Environmental Effects Research
Laboratory (NHEERL), National Exposure Research Laboratory (NERL),
National Risk Management Research Laboratory (NRMRL), National Center
for Environmental Research (NCER), and National Center for
Environmental Assessment (NCEA).[Footnote 27] Specifically, one
laboratory, NHEERL, conducts research on the effects of various
exposure routes and rates, dose levels and duration, and cumulative
doses on health outcomes. Its main research areas, all of which help
improve risk assessments, target (1) the use of mechanistic
information--how a substance causes an effect at a biological level--to
reduce uncertainties in risk assessment; (2) the cumulative risks posed
by exposure to contaminant mixtures; (3) the health risks to
particularly susceptible populations; and (4) the evaluation of public
health outcomes to determine the effectiveness of actions designed to
reduce health risks. This research is developed in coordination with
the program offices to target issues in risk assessment for air
pollutants, safe foods and pesticides, water, and contaminated lands.
A second laboratory, NERL, researches and develops improved methods and
models to assess and predict human exposures to harmful contaminants in
air, water, soil, and food. For example, it developed methods to better
characterize pollution sources, and models to quantify the effects on
exposure from various individual behaviors. NERL works closely with the
program offices to set research priorities and help ensure that its
results are useful to the program offices. For example, NERL
coordinated with OAQPS to format data from several studies on airborne
particulate matter in a comparable manner that allowed NERL and OAQPS
staff to develop more powerful analytic results than would have been
possible from the individual studies alone. NERL also developed tools
to enhance the exposure assessment portion of the risk assessment, such
as a database of human activities by age, sex, and location, to better
characterize exposure risk based on personal activities. The third
laboratory, NRMRL, focuses its research more on ways to minimize
exposure to contaminants that cause health risks than on ways to
improve the preparation of risk assessments. For example, NRMRL
researches sources of chemicals that disrupt the endocrine system and
strategies to minimize exposure to such chemicals.
The two centers, NCER and NCEA, serve as focal points for external
researchers and risk assessors, respectively. NCER funds innovative
environmental research by academic scientists to reduce uncertainty in
risk assessment. Specifically, NCER has sponsored research to develop
data for use in models, thereby helping to reduce the model's
uncertainties. NCER also coordinates with EPA's laboratories and
program offices to develop its research topics. The Science to Achieve
Results (STAR) program, one of NCER's grant programs, funds competitive
research proposals and graduate fellowships in environmental science
and engineering fields to complement ORD's research in its strategic
and research plans, such as the health effects of contaminants on
airborne particulate matter and in drinking water, and, more generally,
on children's health. For example, the STAR program has funded research
to generate data on human exposures that will improve risk estimates.
NCER has also established academic research centers in such areas as
children's health. NCEA, EPA's national resource center for human
health risk assessment, supports EPA's work in three main ways. First,
NCEA conducts risk assessments of national significance--for example,
assessments of dioxin and diesel emissions--and prepares the air
quality criteria documents that reflect the state of the science for
six principal air pollutants. Second, it develops scientifically sound,
defensible risk assessment methods to improve the use of science in
risk assessment, such as software to estimate a benchmark dose--the
dose that produces change in the risk of an adverse effect. Third, it
provides guidance and support to risk assessors and risk managers
through such means as its management of the Integrated Risk Information
Systems (IRIS), a database of the potential human health effects of
exposure to various chemicals in the environment.
In addition to the six labs and centers, EPA in 2005 established the
National Center for Computational Toxicology (NCCT) to coordinate and
implement EPA's research on computational toxicology, a cutting-edge
field that uses mathematical models to predict adverse effects and to
better understand the mechanisms through which a given contaminant
causes harm. Given advances in such newly emerging disciplines as the
study of genes and their functions, computational toxicology offers the
potential for scientists to develop a more detailed understanding of
the risks posed by a much larger number of chemicals than is currently
possible. NCCT research is designed to develop tools to conduct
quantitative risk assessments more rapidly and to improve the
identification of chemicals that may pose substantial health risks.
NCCT staff have begun to collaborate with other ORD laboratories and
centers to effectively target their research efforts.
EPA Has Enhanced Strategic Research Planning:
Since 1994, EPA has undertaken a number of strategic activities to more
closely link the data needs of program offices to research agendas of
EPA and ORD.[Footnote 28] In connection with the goals presented in
EPA's and ORD's strategic plans, ORD defined 16 high-priority research
areas such as human health, endocrine disruption, airborne particulate
matter and other air pollutants, and safe pesticides. Research
strategies for each area are either in place or under development. For
example, EPA's Human Health Research Strategy identifies four broad,
overarching research areas to guide ORD's human health research over
the next 5 to 10 years.[Footnote 29]
To carry out its 16 research strategies, ORD began in 2000 to develop a
multiyear implementation plan for each. The first plans emerged in
2001, with most finalized by 2003 following widespread participation
and input from many stakeholders as well as review by senior ORD
managers. ORD invites input on the plans from ORD and program office
staff, federal research partners, and outside peer groups, such as
EPA's Science Advisory Board, the Board of Scientific Counselors, and
the National Research Council. These plans establish the short-and long-
term goals and timelines required for ORD's laboratories or centers to
implement each of the strategies. The National Program Director, a
newly established position for each major ORD research area including
human health, helps ensure that ORD's time and staff resources are used
strategically and that the overall planning effort links to the needs
of the program offices.
Program offices use various planning and review approaches to determine
data needs. For example, the Office of Air Quality Planning and
Standards develops a research-needs paper at the conclusion of each
periodic review of the air quality standards it establishes to inform
the research agenda for the next review, which occurs about every 5
years. Each paper helps ensure that research in key areas will be
available for the next review. In contrast, the data needs of the
Office of Pesticide Programs are defined by law.[Footnote 30]
Applicants who wish to register a pesticide product must submit the
data defined in the statute and regulations, and OPP staff determine
whether the data are of sufficient quality and quantity to assess the
risk from the pesticide product.[Footnote 31] This list of required
data is currently undergoing revision and additional data requirements
may be added.
EPA Program Offices Have Established Collaborative Relationships with
External Researchers:
Since 1994, EPA has strengthened and formalized collaboration with a
range of other federal researchers to better leverage its limited
research dollars and foster the development of data to improve human
health risk assessments. Specifically, EPA has developed relationships
with agencies such as the National Institute for Environmental Health
Sciences (NIEHS) and the Agency for Toxic Substances and Disease
Registry (ATSDR). For example, in 1998, EPA established a cooperative
agreement with NIEHS to develop a body of research on the relationship
between exposures and children's health. This collaboration jointly
funded Children's Environmental Health Research Centers at seven U.S.
universities and one medical center to research children's asthma and
other respiratory diseases, as well as ways to reduce farm children's
exposure to pesticides. In addition, EPA works closely with ATSDR to
help fill research gaps and develop chemical-specific toxicological
assessments used in risk assessments. In 2004, EPA and ATSDR entered
into a formal agreement to ensure close collaboration to avoid
duplicating efforts to fill data gaps. Under the agreement, the two
agencies formed a work group to coordinate their efforts to develop
toxicological assessments for ATSDR's work at specific highly
contaminated locations and for EPA's Integrated Risk Information System
(IRIS) database.
EPA, NIEHS, and ATSDR also jointly develop and annually review a list
of approximately 275 hazardous substances commonly found at the
nation's highly contaminated sites and for which ATSDR will prepare
toxicological assessments. At each annual review, agency staff may add
chemicals to the list and identify priority research to fill gaps in
knowledge. Of these 275 chemicals, approximately 150 have been
identified by EPA as high-priority needs. Each toxicological assessment
contains almost everything that is known about the chemical, including
its potential to harm human health or the environment. A key difference
between these toxicological assessments and the ones in EPA's IRIS
database is that ATSDR includes chronic cancer and noncancer effects,
as well as acute effects, while IRIS generally includes only chronic
cancer and noncancer effects.
In addition, EPA has begun to establish collaborative relationships
with scientific and industry-related researchers. For example, EPA has
cooperative agreements with the International Life Sciences Institute's
Risk Science Institute (ILSI-RSI), an organization that researches
critical scientific issues in risk assessment, such as the development
of risk assessment methodologies.[Footnote 32] These cooperative
agreements were specifically designed to engage the scientific
community and bring together scientists from different affiliations
(including academia, other parts of government, and the private sector
including industry) to address risk assessment issues. Under one
agreement, ILSI-RSI is to research risk assessment approaches for
cumulative and aggregate exposures. In addition, EPA has used research
provided by CIIT Centers for Health Research, a chemical research
laboratory funded by EPA, industry, and other federal agencies, to
provide information for its formaldehyde IRIS assessment. Furthermore,
EPA and industry jointly fund the Health Effects Institute (HEI)--an
organization that researches the health effects of various air
pollutants, including airborne particulate matter and ozone. HEI has
provided data for risk assessments and convened panels of experts to
review and issue reports related to risk assessment, recently on diesel
exhaust. In its 2004 staff paper, EPA noted that it needs to continue
to encourage development of the specific data necessary to more
accurately assess potential risks, particularly with researchers
responsible for generating appropriate data, such as those seeking
approval to manufacture or use a chemical.
The Office of Pollution Prevention and Toxics has two programs to work
with industry to develop data on contaminants that can be used to
better understand risks. The first is the High Production Volume (HPV)
Challenge Program. This program was officially launched in late 1998 to
ensure that a baseline set of data would be made available to the
public on approximately 2,800 chemicals that are manufactured or
imported in amounts greater than 1 million pounds per year. Diverse
stakeholders, including the American Chemistry Council, Environmental
Defense, and the American Petroleum Institute participate in the
program. The HPV Challenge Program provides an opportunity for all
stakeholders, including the public, to comment on the tests and data
summaries from the chemical sponsors--companies and consortia that
volunteered to make publicly available screening-level data that allow
EPA, industry, and other stakeholders to more effectively gauge the
potential hazards of HPV chemicals. All comments are publicly available
on the World Wide Web. As of January 2006, EPA had commitments from
industry sponsors to provide data for 2,247 of the chemicals. The
second program, the Voluntary Children's Chemical Evaluation Program,
is designed to provide data that will allow the public to better
understand the potential health risks to children associated with
certain chemical exposures. EPA asked companies that manufacture or
import 23 chemicals that have been found in human tissues in various
biological monitoring programs to voluntarily sponsor the evaluation of
specific chemicals in a pilot program. Thirty-five companies and 10
consortia volunteered to sponsor 20 chemicals. This program was
developed only after considering comments and concerns from
stakeholders. Of the 23 chemicals chosen for this pilot, data gathering
has been completed for 9 and is under way for another 11. The remaining
3 chemicals in the pilot program have no sponsors.
EPA Maintains Databases of Information Related to Risk Assessment:
EPA maintains both an agencywide and several program-specific databases
of information to help in the development of risk assessments. The
primary database used by risk assessors in the program offices is the
Integrated Risk Information System (IRIS), an electronic database of
descriptive and quantitative information on human health effects that
may result from exposure to various chemicals in the environment.
Program office staff combine the IRIS data with exposure information
they develop to characterize the health risks of a given chemical in a
given situation.
Since 1994, EPA has changed the IRIS assessment process in several
ways. For example, each IRIS file now contains a discussion of the key
studies, as well as a description of the decisions and default
assumptions used in the assessment. EPA has also expanded the review
that IRIS assessments undergo. For example, internal peer reviewers,
including EPA senior health scientists representing program offices and
regions, review the IRIS summary and accompanying detailed technical
information. After this review, ORD releases the document for external
peer review. EPA makes draft assessments available to the public at
this time and, following peer review, the IRIS assessment discusses the
key issues reviewers raised and EPA's response. In addition, EPA has
added a tracking system that allows IRIS users to readily determine
where an individual assessment is in its development.
In September 2003, EPA completed a congressionally requested review to
assess the need to update information in IRIS, based on concerns that
EPA and state regulators rely on potentially outdated scientific
information. Input from EPA program and regional offices, the public,
and other stakeholders indicated that EPA should, among other things,
increase the number of new or updated assessments completed each year
to 50. To date, EPA has fallen considerably short of this goal.
According to a program official, EPA completed 8 IRIS assessments in
2005, plans to complete 16 in 2006, and has approximately 75
assessments under way. EPA officials said a number of factors, such as
the complexity of the assessment process, resource limitations, and
extensive peer review, had limited EPA's ability to complete more
assessments last year. EPA has increased the number of staff working on
IRIS assessments from 6 to 23 and may ultimately increase the number to
29. The review also indicated that EPA needs to assign staff to develop
health assessments for IRIS, and provide funding for extramural
research and contracts to develop IRIS files and subject them to
external peer review.
EPA also changed how it sets priorities for which chemicals need new or
updated IRIS assessments.[Footnote 33] Annually, EPA asks its program
offices, regions, and the public to identify contaminants for which it
should develop or revise IRIS assessments. EPA publishes the list in
the Federal Register and requests the public and scientific community
to submit any relevant data on substances undergoing review. EPA is
currently reviewing ways to increase coordination with other
governmental agencies that develop chemical assessments, outreach to
stakeholders earlier in the development of IRIS assessments, and
consultation with independent external reviewers. In 2004, the IRIS
program also initiated a review of available scientific literature for
the 460 chemicals in the database that are not under active
reassessment to determine whether a reassessment based on new
literature could significantly change existing toxicity information.
For 63 percent of the chemicals reviewed, no major new health effects
studies were found. Such literature reviews will be conducted annually
and the findings noted in the IRIS database.
In addition, some program offices maintain databases to enhance their
risk assessments. For example, the Office of Air Quality Planning and
Standards (OAQPS) maintains a database of dose-response values
developed by various sources, including IRIS, ATSDR, and the California
Environmental Protection Agency, as an aide for its risk assessors.
OAQPS staff update this database as better data become available. As
part of its National Air Toxics Assessment--an ongoing comprehensive
evaluation of hazardous air pollutants in the United States--EPA
assessed 32 air pollutants plus particulate matter in diesel exhaust in
1996. The national assessment is designed to identify air pollutants
with the greatest potential to harm human health, and the results will
help set priorities for collecting additional data. As part of its
assessment, EPA compiled a national emissions inventory of hazardous
air pollutants from outdoor sources, estimated population exposures to
the pollutants, and characterized the potential cancer and noncancer
health risks from breathing the pollutants.
ORD also maintains personal monitoring data on the chemicals in the
air, foods and beverages, water, and dust in an individual's personal
indoor and outdoor environments. For example, in its National Human
Exposure Assessment Survey (NHEXAS) program, which was completed in
1998, ORD collected human exposure data from hundreds of subjects from
several areas of the country. NHEXAS provided data on background levels
of total exposure to environmental contaminants that can be used as a
baseline in exposure and risk assessments to estimate whether specific
populations are exposed to increased levels of environmental
contaminants.
EPA Has Improved Its Choice and Communication of Default Options:
EPA has explicitly stated the need for risk assessors to identify when
they relied on a default option, why they chose it, and when they
departed from using a standard default option, but the agency
acknowledges more could be done. To carry out its mission to protect
human health, EPA's risk assessment procedures, including its default
options, are protective of human health. In three recent guidance
documents--the 2004 staff paper, the 2005 cancer guidelines, and the
risk characterization handbook--EPA advocated more transparency in the
choice of default options. These documents summarize a significant
change in EPA's approach. Specifically, EPA first critically examines
all relevant and available data to assess health risks, then uses the
default options only in the absence of adequate contaminant-specific
data. EPA also states in its staff paper that it bases its default
assumptions on peer reviewed published studies, empirical observations,
extrapolation from related observations, and scientific theory.
Moreover, the cancer guidelines include an appendix that defines the
basis for each of the default options that may be used in a cancer risk
assessment. The Risk Characterization Handbook notes that risk
assessments should describe the full range of default options that were
used, including ones to address uncertainty. Moreover, the handbook
states that when defaults are used, the risk assessment should
reference the relevant EPA guidance that explains them.
EPA program offices also advocate greater transparency when using
default options. Specifically, the majority of IRIS assessments
completed since 1997 describe the defaults used in the analysis and any
departures from those defaults. The Office of Air Quality Planning and
Standard's Air Toxics Risk Assessment Reference Library contains a
number of references to defaults that should be used in the course of
preparing a human health risk assessment.[Footnote 34] For example, to
estimate an individual's exposure to an air pollutant, the guidance
presents the default option to use for exposure in a screening-level
assessment, namely that the individual remains at a single location and
continuously breathes polluted air.
Despite the increased focus on more transparency in the use of
defaults, EPA acknowledges it could more consistently describe how the
default was developed and explain why it is a reasonable assumption. In
its staff paper, EPA acknowledges it needs to ensure that the defaults
are supported by the best available data and should look for
opportunities to increase certainty and confidence in the defaults and
extrapolations used. EPA also acknowledges it may need to re-examine
older risk assessments that relied on defaults that can now be replaced
with relevant data. To a large degree, the use of defaults is
intertwined with EPA's ability to get the data it needs. As was
discussed previously, EPA has targeted research, both within EPA and
through its grant programs, to understand variability and uncertainty
in the data derived from studies of laboratory animals, and this
research may further reduce EPA's need to rely on default options.
EPA Has Taken Steps to Enhance Its Modeling Capabilities and Embrace
New Methodologies:
Since 1994, EPA has taken several steps to enhance its modeling
capabilities and embrace new methodologies for risk assessment through
improved guidance and workshops. To help improve its models, EPA's
Agency Task Force on Environmental Regulatory Modeling published a
report that concluded a need existed for, among other things, training
and technical support, agency guidance on external peer review of
environmental regulatory modeling, and creation of a Committee on
Regulatory Environmental Modeling.[Footnote 35] Also in 1994, EPA's
Risk Assessment Forum developed a draft protocol to evaluate models for
exposure assessments.[Footnote 36] In 1997, ORD and program offices
conducted an agencywide conference, called the Models 2000 Workshop, to
facilitate adherence to existing guidance on modeling, to define and
implement improvements in how the agency developed and used models, and
to recommend an implementation plan for improving modeling within the
agency.
EPA followed up these activities in 2000 by creating the Committee on
Regulatory Environmental Modeling (CREM) to promote consistency and
consensus within the agency on modeling issues (including modeling
guidance, development, and application) and to enhance internal and
external communications on modeling activities. CREM supports and
enhances the existing modeling activities in the program offices and
provides EPA with tools to support environmental decision making. CREM
also provides the public and EPA staff with a central point of inquiry
about EPA's use of models. In 2000, CREM launched agencywide activities
designed to enhance the development, use, and selection of regulatory
environmental models at EPA. One such activity--a workshop to
facilitate discussion of good modeling practices--resulted in the
development of modeling guidance.
In 2003, CREM developed guidance and created a database--called the
Models Knowledge Base--of the models most frequently used in
EPA.[Footnote 37] The guidance recommends best practices to help
determine when a model, despite its uncertainties, can be appropriately
used to inform a decision. Specifically, it recommends that model
developers and users subject their model to credible, objective peer
review, assess the quality of the data they use as inputs, and perform
sensitivity and uncertainty analysis to determine which of the model
inputs has the greatest impact on the modeled results.
EPA has also incorporated efforts to improve models in its research
strategies and implementation plans. For example, in its plan for
research on hazardous air pollutants, EPA established a long-term goal
to reduce uncertainties in risk assessments through methods, data, and
models of acute and chronic exposures and exposures through multiple
pathways at both the national and regional levels. In addition, one of
ORD's laboratories established an exposure modeling research branch and
develops population exposure models, such as the Stochastic Human
Exposure and Dose Simulation model for inhalation and exposures of
general and sensitive subpopulations through multiple pathways. EPA has
also begun to use geographic information systems (GIS) to present risk
information spatially. For example, a GIS system is being developed
that maps all of the drinking water intakes in the United States and
their associated watersheds, so that the agency can better assess risks
to drinking water supplies stemming from activities in the related
watershed. For risk assessments of hazardous air pollutants, GIS can
display and analyze data during planning, scoping, and problem
formulation, during the exposure assessment, and during the
characterization of risks. GIS can also help communicate information to
risk managers and other stakeholders.
In addition to models, EPA is beginning to embrace such new risk
assessment methodologies as probabilistic risk assessment and mode of
action analysis. Probabilistic risk assessment characterizes the
variability or uncertainty in risk estimates as the range or
distribution of the number of times each possible outcome will occur.
In probabilistic risk assessment, one or more variables in the risk
equation, such as the exposure rate, is defined as a distribution
rather than as a single number. A primary advantage of probabilistic
risk assessment is that it provides a quantitative description of the
degree of variability or uncertainty. EPA's 1997 policy states that
probabilistic techniques, such as Monte Carlo analysis, can be viable
statistical tools to analyze variability in risk assessments, when they
are based on adequate supporting data and credible
assumptions.[Footnote 38] The guidance presents a general framework and
broad set of principles to ensure the use of good scientific practices
when conducting probabilistic analyses of variability and uncertainty.
EPA currently uses a number of models that include probabilistic
analyses and is developing a new modeling framework, known as the
Multimedia Integrated Modeling System, that will further enhance the
agency's ability to probabilistically model uncertainty.
EPA's recently revised cancer guidelines advocate the use of a mode of
action analysis--based on the sequence of biological events that must
occur to produce a harmful effect--to improve the accuracy of risk
assessments. As a general rule, EPA assumes that toxic responses
observed in laboratory animals indicate that the same responses are
likely to occur in people even though differences in such areas as
metabolic rates can result in different sensitivities between
laboratory animals and humans. Mode of action analysis will more
clearly indicate whether a difference exists between animals and humans
in their response to contaminants. In addition, the guidelines present
a new cancer characterization system consisting of five summary
descriptors, to be used in conjunction with narrative, to describe the
extent to which available data support the conclusion that a
contaminant causes cancer in humans and to justify the summary
descriptor selected. For noncancer risk assessments, EPA has used, and
continues to refine, the benchmark dose methodology, which identifies
the dose or concentration of a contaminant that slightly increases the
likelihood of an adverse effect.
EPA Is Introducing More Quantitative Characterization of Uncertainty
into Its Risk Assessments:
Uncertainty is inherent in all phases of risk assessment, from hazard
identification through risk characterization. Over the years, EPA has
relied more on qualitative, or descriptive, characterizations of
uncertainty and less on quantitative, or numeric, characterizations.
EPA's practice now is to use a tiered approach to analyze uncertainty.
That is, EPA starts with a simple description of uncertainty and
sequentially employs more sophisticated quantitative analysis, such as
sensitivity analysis, provided the additional analysis reduces the
uncertainty. To characterize risk quantitatively, EPA has typically
used approaches that produce a single number to characterize the risk
in terms of the level of a contaminant that does not cause harm, as
opposed to presenting a range of possible values.
Although EPA is beginning to use probabilistic approaches in exposure
assessments, and has done so for six principal air pollutants, it does
not typically do so to analyze uncertainty in its dose-response
analyses, though its Science Advisory Board encouraged development of
such approaches in 2000. EPA acknowledged in its 2004 staff paper that
probabilistic risk assessment could be used more frequently and could
provide useful information beyond screening-level assessments. However,
the staff paper said probabilistic analysis may not be appropriate in
all situations and the accuracy of the analysis will depend largely on
the availability and quality of the data used in the analysis.
Another quantitative approach to uncertainty is the use of uncertainty
factors to account for such unknowns as variation in sensitivity among
members of the human population or the appropriateness of extrapolating
animal data to humans. EPA routinely uses uncertainty factors when it
estimates the daily exposure to the human population that is likely to
be without appreciable risk of adverse effects during a lifetime. This
daily exposure estimate is called a reference dose for contaminants
that are consumed and a reference concentration for inhaled
contaminants. EPA states in its 2004 staff paper that it applies
uncertainty factors in health assessments based on available data and
the scientific judgment of EPA risk assessors and peer reviewers.
According to EPA, most IRIS toxicological assessments, which contain a
chemical's reference dose and reference concentration, provide
justifications for the uncertainty factors applied to a particular
chemical. Moreover, the factors undergo rigorous internal, and
independent, external scientific peer review before being used in IRIS
assessments.
EPA has issued a number of documents that delineate the need to clearly
and consistently characterize uncertainty in risk assessments. In 1995,
EPA issued a risk characterization policy that stated that the risk
assessment should fully, openly, and clearly characterize risks, and
should disclose the scientific analyses, uncertainties, assumptions,
and policies underlying the decisions. This policy was followed in
December 2000 by the Risk Characterization Handbook, which includes
guidance on how to address, among other things, uncertainty in risk
assessment and describes the need and methods to present the sources
and magnitude of uncertainty to the risk manager. More recently, the
2005 revised cancer guidelines discuss each of the major uncertainties,
such as model uncertainty or uncertainty related to human variation,
and stress that assessments should discuss the significant
uncertainties encountered in the analysis. For example, the guidance
calls for the assessments of hazard, dose-response, and exposure to
have accompanying technical characterizations covering the strengths
and limitations of data and a discussion of uncertainty.
EPA Better Analyzes and Communicates Variability in both Exposure and
Susceptibility:
EPA has made progress in describing variability due to differences in
both the exposure individuals receive and the susceptibility of exposed
individuals to adverse effects. A key document EPA risk assessors use
to account for variation in exposure is its Exposure Factors Handbook,
originally issued in 1989 and revised in 1997. The handbook summarizes
data on human behaviors and characteristics that influence exposure to
environmental contaminants and recommends values to account for those
factors in assessing risk. Specifically, the handbook contains a series
of over 150 data tables that provide information on how much time
individuals spend at various activities and in various environments.
Assessors can use these data to develop exposure duration estimates for
exposure scenarios. For example, the tables contain statistics--broken
down by age, gender, race, education, and some medical conditions, such
as asthma or emphysema--for time spent in various outdoor locations.
The handbook also provides general guidance to risk assessors on the
types of variability relevant to a risk assessment and ways variability
can be analyzed and addressed.
All program offices address exposure variability in their risk
assessments, although they do so in different ways. For example, risk
assessors in the Office of Air Quality Planning and Standards who set
certain air quality standards for six principal pollutants said they
consider individual activity patterns for sensitive populations like
children or asthmatics in exposure modeling by including a distribution
of breathing rates to reflect variability inherent in the population.
Furthermore, by modeling to protect the most sensitive or at-risks
groups, they are assured of protecting the rest of the population.
Variability in exposure to the six principal pollutants is generally
described qualitatively in scientific summaries for each pollutant. The
Office of Water includes an analysis of risks to various subpopulations
and a narrative discussion of the strengths and weaknesses of the
studies it used to estimate exposure, but generally does not include a
quantitative analysis. The Office of Pesticide Programs considers 24
different population subgroups in its exposure estimates, including
differences in age, gender, ethnicity, and geographic dispersion. When
data allow, the Office of Pesticide Programs develops a distribution of
exposures and risks for its more refined risk assessments.
To further its understanding of variability in exposure, EPA has
undertaken a number of research projects. For example, one of ORD's
laboratories conducted the National Human Activity Pattern Survey to
provide detailed human exposure information for specific populations
and allow EPA to better understand actual human exposure to pollutants
in real-world situations. The survey results are stored in the
Consolidated Human Activity Database to help risk assessors estimate
the time that exposed people spend in various environments and their
inhalation, ingestion, and dermal absorption rates while in those
environments. This laboratory also conducts research to define,
quantify, and reduce the uncertainty associated with the exposure and
risk assessments, to develop improved methods to more accurately
measure exposure and dose, and to develop technical information and
quantitative tools to predict the nature and magnitude of human
exposures to environmental contaminants. A recent EPA study was
designed to identify chemicals commonly used in homes or day care
centers, and whether children in these environments encountered the
chemicals in the course of their daily activities.[Footnote 39] The
research sought to identify the major routes (i.e., breathing and
ingestion) and sources (i.e., dust, food, air, soil, and water) through
which children come into contact with chemicals.
Variability also exists with regard to susceptibility to adverse
affects because of inherent differences among humans. EPA most recently
addressed variability in susceptibility in the 2005 revision of its
cancer guidelines, which describe the importance of separate risk
assessments for all potentially sensitive life stages, including adults
and children. The supplementary cancer guidelines for children address
issues pertaining to cancer risks associated with early-life exposures.
Legislation can also require EPA to consider potentially susceptible
populations and life stages. For example, the Safe Drinking Water Act
Amendments mandate that EPA consider risks to groups within the general
population that are at greater risk of adverse health effects,
including children, the elderly, and people with serious illnesses. In
addition, the Food Quality Protection Act contains special provisions
for the consideration of risks to children from pesticides. In 1995,
EPA's Science Policy Council called for EPA to consider the risks to
infants and children consistently and explicitly as part of its risk
assessments. In 1997, the White House issued an executive order that
required EPA and other federal agencies to identify and assess
environmental health and safety risks that may disproportionately
affect children and to ensure that policies, programs, activities, and
standards address such disproportionate risks.[Footnote 40]
In its 2004 staff paper, EPA acknowledges that characterizing
variability for susceptible populations and life stages is an area
where it could improve, although the absence of data limits its
efforts. In 2002, EPA pointed out that data are limited to identify
susceptible populations and life stages for many contaminants.[Footnote
41] In these situations, EPA typically relies on default options, such
as the use of uncertainty factors to account for variations in
susceptibility. Many of the exposure assumptions and default values
used to assess plausible current and future exposure scenarios can be
found in EPA's 1997 Exposure Factors Handbook, and recent updates to
the handbook are available online.
Another way EPA addresses variability is through research. One of ORD's
four strategic research directions in its Human Health Research
Strategy is designed to improve the understanding of why some people
and groups are more susceptible and highly exposed than others.
According to this strategy, ORD's research on subpopulations will focus
on three factors--life stage, genetic factors, and pre-existing
diseases--that have been identified by a program office and the
scientific community as having a high priority for risk assessment. In
2000, ORD released its Strategy for Research on Environmental Risks to
Children to strengthen the scientific foundation of risk assessment and
management decisions that affect children and guide EPA's research
needs and priorities over the following 5 to 10 years. Approximately 75
percent of the funding for this strategy will be dedicated to research
grants under the STAR program, such as those designed to evaluate
children's exposure to pesticides.
EPA Has Begun to Consider the Combined Effects of Exposure to Multiple
Contaminants through Multiple Pathways:
To help risk assessors analyze the health effects of exposure to
multiple contaminants (cumulative exposure) and through multiple routes
(aggregate exposure), EPA has issued guidance, developed methods and
models, and supported research. In 1997, EPA's Science Policy Council
issued guidance on cumulative risk assessment. This guidance directs
each office to consider cumulative risk in planning major risk
assessments and, where relevant data are available, to broaden the
scope of the assessment to integrate multiple sources, effects,
pathways, stressors, and populations for cumulative risk analyses. The
guidance also highlights the need to ensure that the public and other
stakeholders have an opportunity to help define the way EPA assesses an
environmental or public health problem and calls for ongoing
communication and coordination among EPA's risk assessors, risk
managers, economists, engineers, and other technical experts.
In 2000, EPA updated its 1986 guidance on chemical mixtures, to
generate a consistent agencywide approach to assess health risks from
exposures to multiple chemicals.[Footnote 42] The guidance is organized
according to the type of data available to risk assessors, ranging from
data-rich to data-poor situations, to help risk assessors select an
appropriate methodology. For example, if data are of poor quality or
quantitative data are very limited on chemical mixtures, the risk
assessor may choose to perform a qualitative analysis of the potential
human health impacts from exposure to the mixture. The guidance also
contains procedures to develop toxicity equivalency factors, based on
the toxicity of components of the mixture, to assess the risk from
mixtures in the absence of data on the specific mixture.
In 2003, EPA's Risk Assessment Forum developed a simple, flexible
framework to help risk assessors consistently conduct and evaluate
cumulative risk assessments.[Footnote 43] The framework is conceptually
similar to the one used in human health assessments of a single
contaminant in that it follows a three-stage approach of (1) planning,
scoping, and problem formulation; (2) analysis; and (3) risk
characterization. In addition, the document also highlights needed
areas of research and methods development that may be important to the
evaluation of cumulative risks, such as understanding how the sequence
and timing of exposure may influence the ultimate risk for effects.
EPA risk assessors use a number of models and methodologies to analyze
multiple routes of exposure. For example, the branch of the Office of
Air Quality Planning and Standards that regulates hazardous air
pollutants employs the Multiple Pathways of Exposure model to assess
and predict the movement and behavior of chemicals in the environment.
For example, the Multiple Pathways of Exposure model includes
procedures to estimate human exposures and health risks that result
from the transfer of pollutants from the air to soil and surface water
bodies and the subsequent uptake of the pollutant by plants, animals,
and humans. The model specifically addresses exposures from breathing;
consuming food, water, and soil; and contact with skin. More recently,
EPA developed the Total Risk Integrated Methodology (TRIM) and created
the TRIM Fate, Transport, and Ecological Exposure model that describes
the movement of air pollutants emitted from any type of stationary
source as well as their transformation over time in water, air and
soil.
Some program offices have also taken steps to explicitly consider the
risks associated with more than one route of exposure or more than one
chemical. Specifically, the Office of Pesticide Programs issued
guidance in 2001 and 2002 in response to statutory requirements to
assess the risk of aggregate exposure--exposure to a single chemical by
multiple pathways and routes.[Footnote 44] The first set of guidance
focuses on how to assess aggregate risk in those cases where more
extensive data and more sophisticated exposure assessment methods and
tools are available; this guidance also emphasizes, when data are
available, the use of distributional data--aggregate exposures of many
individuals in the population of interest--for all pathways of
exposure.[Footnote 45] This approach allows the risk assessor to more
fully evaluate exposure and resulting risk across the entire
population, rather than the exposure of a single highly exposed
individual. The second set of guidance describes a framework to assess
potential human health risks from all pathways of exposure to multiple
pesticides that share a common mechanism of toxicity--that is, the
pesticides produce a similar toxic effect on the same organ or
tissue.[Footnote 46]
In addition, the branch of the Office of Air Quality Planning and
Standards that regulates hazardous air pollutants developed the
Integrated Urban Air Toxics Strategy, which is used to consider
cumulative risks presented by exposures to hazardous air pollutants
emitted from various sources. Staff can assess risk at both a national
and an urban or a neighborhood scale. Furthermore, the hazardous air
pollutant office developed guidance on multipathway risk assessments
that are particularly important for hazardous air pollutants, such as
mercury and dioxins, because human exposure occurs both from breathing
air containing the toxins and from consuming plants, water, and soil
where the pollutants were deposited. Moreover, these pollutants persist
in the environment for long periods of time and may also accumulate in
the tissues of commonly consumed plants and animals to levels that are
harmful to humans.[Footnote 47] The guidance, maintained in the Air
Toxics Risk Assessment Reference Library, describes how to plan, scope,
and formulate the problem, conduct the analysis, and characterize the
risk for such cases.
The extent to which program offices assess the effects of cumulative
and aggregate exposures is related to the regulatory responsibilities
of each office and by the availability of data. For example, the
hazardous air pollutant office routinely analyzes a mix of chemicals
from various emitting sources, such as petroleum refineries, to
regulate hazardous air pollutants.[Footnote 48] Similarly, as mentioned
above, the Office of Pesticide Programs is required to consider
exposure to pesticides from various pathways, such as food, drinking
water, and residential uses, and various routes, such as eating,
breathing, and contact with skin. In contrast, the Toxic Substances
Control Act does not require the Office of Pollution Prevention and
Toxics to assess the risks of a new chemical that may occur through its
interaction with other chemicals. The office also assesses the risks of
existing chemicals but cannot conduct cumulative risk assessment for
classes of chemical that share a common mode of action because no data
exist. Program managers hope such data will become available in the
future.
In its 2004 staff paper, EPA commented that while it has increased its
emphasis on evaluating cumulative risks, it needs to expand on
approaches to do so, and it needs to produce a rigorous scientific base
to support such evaluations. To that end, one of ORD's four strategic
research directions in its Human Health Research Strategy is to improve
assessments of aggregate and cumulative risks. Specific research
objectives are to develop exposure models and methods, provide a
scientific basis to predict interactive effects of contaminants in
mixtures, and determine the most appropriate approaches to combine
effects and risks from mixtures.
EPA Risk Assessors Responding to Our Survey Reported That Process
Modifications Have Helped Them Prepare Better Risk Assessments but That
Collaboration and Training Limitations Hamper Further Progress:
EPA risk assessors responding to our survey reported that some
modifications to its risk assessment processes, such as new or updated
EPA guidance issued over the last 10 years, have been helpful. They
also said that although collaboration among internal and external
researchers has improved, problems remain with communication and
coordination. Finally, risk assessors said that the training they've
taken in the last 5 years has been beneficial, but they need additional
training on analytic tools, such as modeling, and on other scientific
disciplines related to risk assessment.
EPA Has Issued Numerous Guidance Documents That Have Been Generally
Helpful to Risk Assessors:
At least two-thirds of risk assessors responding to our survey who
reported using guidelines or reference documents indicated that these
documents were moderately to very helpful in preparing risk
assessments.[Footnote 49] In addition, between one-third and two-thirds
of respondents who reported using policy documents said these documents
were moderately to very helpful in preparing risk assessments. More
specifically, many risk assessors said agencywide guidelines and
reference documents provide a framework to assess risks to human health
that help make risk assessments more consistent. For example, some risk
assessors noted the usefulness of agency reviewed or approved
procedures to support their assessments. In addition, some risk
assessors said the guidelines and reference documents helped clarify
issues, and several assessors said they were a good source for data
needed to conduct assessments. Risk assessors responding to our survey
cited the Guidelines for Carcinogen Risk Assessment as the document
most frequently used when preparing human health risk assessments. More
specifically, several risk assessors noted that the carcinogen
guidelines provide a useful framework for preparing risk assessments.
Many risk assessors commented that agencywide guidelines and reference
documents are helpful or provide useful examples. For example, a few
risk assessors stated that the Exposure Factors Handbook helps provide
consistency among EPA offices that conduct exposure assessments because
it defines standard values for exposure, and the rationale behind those
values. Another assessor said that the Review of the Reference Dose and
Reference Concentration Processes provides comprehensive guidance on
setting reference values and contains a case study that serves as a
model for concise and well-written hazard identification. Although risk
assessors responding to our survey reported that guidance documents are
generally helpful, many expressed concerns about them. For example,
some risk assessors consider the documents too general or too difficult
to decipher.
In addition, 82 percent of the risk assessors whose offices have office-
specific guidance said that the guidance is very or moderately helpful
with regard to preparing risk assessments. (See fig. 2.) According to
many risk assessors, office-specific guidance provides information in a
format relevant to each office's specific needs. For example, the
Office of Pesticide Programs periodically issues "hot sheets" that
describe how to apply general guidance to pesticide product risk
assessments. In addition, the Office of Air and Radiation created the
Air Toxics Risk Assessment Reference Library that provides information
on how to analyze the risks from hazardous air pollutants. Over 65
percent of risk assessors reported that EPA and program offices were
moderately to very effective at disseminating guidance.
Figure 2: Helpfulness of Office-Specific Guidance:
[See PDF for image]
Source: GAO analysis of survey data.
Note: Percentages do not total to 100 because of some risk assessors
did not respond to this question.
[End of figure]
Collaboration Has Improved EPA's Ability to Conduct Risk Assessment,
but Problems Remain:
To prepare risk assessments, EPA relies on external peer review and
scientific data from a variety of sources on the potential health risks
from exposure to contaminants. Collectively, this collaboration has
improved EPA's ability to conduct those assessments. For example, 35
percent of risk assessors responding to our survey reported that
external peer review, which is often conducted by independent
researchers, has definitely helped improve the overall quality of EPA's
risk assessments, with an additional 48 percent noting that it has
probably helped improve the overall quality. Furthermore, at least 32
percent noted that peer review has definitely helped ensure that the
science used in risk assessments is appropriately characterized, helped
advance the use of new scientific methods or models, and helped EPA
produce risk assessments that are more defensible. Another 38 percent
said that peer review has probably helped with these improvements. In
addition, responding EPA risk assessors rely primarily on other federal
research entities, academia, and industry, and to a slightly lesser
extent, ORD's research laboratories, to meet their offices' research
needs. (See fig. 3.)
Figure 3: :
[See PDF for image]
[End of figure]
Figure 4: Risk Assessors That Generally or Strongly Agree That
Organizations Help Fill Data Needs:
[See PDF for image]
Source: GAO analysis of survey data.
[End of figure]
More specifically, 63 percent of risk assessors generally or strongly
agreed that they relied on other federal research entities, such as the
National Toxicology Program; [Footnote 50] the National Institute for
Environmental Health Sciences (NIEHS) and the National Cancer
Institute--both within the National Institutes of Health; and the
Agency for Toxic Substances and Disease Registry (ATSDR) to help fill
their offices' needs for scientific data. EPA has established formal
collaborative agreements with both NIEHS and ATSDR to research
children's health and to develop toxicological data useful to both
agencies, respectively. In addition, EPA has also collaborated with the
U.S. Geological Service to identify contaminants in ground and surface
waters.
In addition to federal research entities, over 57 percent of
respondents generally or strongly agreed that their offices rely on
research from academia and industry to meet their research needs. For
example, EPA has formal agreements with the International Life Sciences
Institute's Risk Science Institute and the Health Effects Institute to
develop research on approaches to analyze cumulative and aggregate
exposures and the health effects of various air pollutants,
respectively. EPA also relies heavily on industry-generated research on
specific chemical substances. For example, under the laws that govern
registration of pesticide products and new chemicals, applicants must
supply specific data for relevant EPA offices to review when deciding
whether to approve the pesticide products or chemicals in question.
Furthermore, 46 percent of risk assessors said they relied on ORD's
laboratories to generate research that helps fill scientific data
needs. For example, some risk assessors said scientists from ORD's
laboratories provide useful technical guidance on scientific issues or
the risk assessment process. Another risk assessor commented that ORD's
expertise is very useful to help interpret unusual findings or to
advise on emerging issues. One risk assessor stated that ORD helped
develop a specific model to use in probabilistic risk assessments.
Other types of collaboration with ORD's laboratories include help to
develop models for assessing dose and response relationships, to
interpret toxicity data, to conduct epidemiological studies, and to
develop scientific summaries for risk assessments of priority air
pollutants.
Overall, of the risk assessors who said they often or always
collaborate with other EPA offices, at least 46 percent said that the
collaboration was very effective. A few risk assessors commented that
collaboration has become more effective in recent years, in part
because staff in the various offices have more contact with one other,
established scientist-to-scientist relationships, or learned whom to
contact to address a particular question. For example, one risk
assessor pointed out that cross-agency workgroups help to facilitate
agencywide collaboration. Furthermore, a few risk assessors commented
that the program offices' knowledge of the regulatory context in which
research will be used helps ORD's researchers structure their work. For
example, NERL collaborated with the Office of Air to fund studies that
coordinated the format of data produced by different researchers to
enhance the consistency of research approaches, which created more
powerful results and made the data more useful to program offices.
Finally, because some chemicals may be assessed by more than one
office, collaboration across program offices helps ensure the
consistency of risk assessments across EPA. For example, the Office of
Pesticide Programs and the Office of Water may both prepare risk
assessments for certain contaminants that may be found on food and in
drinking water.
Despite the improvements to collaboration at EPA, some risk assessors
pointed out two barriers that limit collaboration. Specifically,
assessors noted that conflicting priorities or goals among EPA offices
and poor communication between some offices hinder the effectiveness of
collaboration. For example, although some chemicals are studied by more
than one office within EPA, the approaches and timelines differ among
offices because the laws and responsibilities for each program office
can differ significantly. As a result, what may be a priority chemical
in one program office may not be a priority in another, thereby
hindering timely collaboration. Furthermore, a couple of risk assessors
found collaboration challenging because they could not find the right
person in another office to communicate with on a specific issue.
Several risk assessors suggested ways to improve and increase
communication among program offices, ORD, and non-EPA organizations.
For example, some risk assessors suggested more interagency work groups
or meetings as a way to address research needs and foster information
exchange on the development of methods. A few risk assessors suggested
that a central library of risk assessment information would facilitate
collaboration and avoid duplicating work already done by others.
Specifically, one risk assessor said EPA could provide centralized
databases of work conducted by different agencies and organizations,
such as chemical-specific toxicity data, specific exposure or other
values, and points of contact at each office.
EPA's Training Has Been Helpful, but Risk Assessors and Managers Lack
Sufficient Training on Analytic Tools and Emerging Issues:
At least 80 percent of risk assessors responding to our survey said
that the training they received, whether on the job, self-directed,
office specific, or agencywide, was moderately to very useful.
Moreover, over half of these risk assessors said that training improved
their ability to prepare risk assessments. Nevertheless, risk assessors
surveyed and agency officials interviewed reported that both risk
assessors and managers would benefit from more in-depth training on
subjects such as analytic tools and emerging scientific issues.
Risk Assessors Have Enhanced Their Skills through Training in Various
Areas:
Over half of the risk assessors reported that training had moderately
or greatly improved their abilities in at least seven different risk
assessment skill and knowledge areas. More specifically, over 75
percent of risk assessors reported that training has helped them learn
about a particular risk assessment method or model, enhance the quality
of risk assessments or risk characterizations they prepare, and
maintain or refresh their existing knowledge (see fig. 4). To a
slightly lesser extent, training also helped risk assessors apply EPA
guidance and policies, more effectively prepare risk assessments, and
understand EPA's four-stage paradigm for risk assessment.
Figure 5: Areas in Which Training Has Moderately or Greatly Improved
Risk Assessor Knowledge and Skills:
[See PDF for image]
Source: GAO analysis of survey data.
[End of figure]
Over three-quarters of risk assessors reported that they participated
in on-the-job (82 percent) or self-directed (77 percent) training to
enhance their skills. (See fig. 5.) According to risk assessors in the
office that reviews new chemical applications, training is primarily on
the job, largely because the office makes risk assessment decisions
under tight time frames, which limits the time available for formal
training, according to program officials. Similarly, workload
constraints affect opportunities for formal training at the Office of
Water, which instead relies primarily on self-directed or on-the-job
training. Some on-the-job training takes the form of mentoring, such as
in the Office of Research and Development, where senior staff are
expected to mentor newer staff.
Figure 6: Types of Training Taken by Risk Assessors:
[See PDF for image]
Source: GAO analysis of survey data.
[End of figure]
In addition, over 70 percent of risk assessors who responded to our
survey reported that they participated in office-specific training to
enhance their risk assessment skills. For example, the Office of
Pesticide Programs (OPP) has a comprehensive risk assessment training
program focusing mostly on scientific issues, but also on other issues
to improve the overall quality of risk assessments. This training
features speakers, including some from outside OPP, such as from other
EPA offices, academia, and industry. These biweekly sessions are
broadcast live over the office's internal computer system and taped for
future use as well as broader distribution, so that staff can access
them as needed. Moreover, OPP's training program includes having
experienced risk assessors nearing retirement share their knowledge
with other staff. Of the risk assessors responding to our survey that
work in OPP, over 90 percent took advantage of its office-specific
training. A similarly high percentage of staff in the hazardous air
pollutant branch of the Office of Air and Radiation reported that they
took that office's training on preparing risk assessments.
In addition, 50 percent of risk assessors said they attended external
training, such as professional society meetings sponsored by the
Society for Risk Analysis, Health Effects Institute, and the Society of
Toxicology and university courses related to scientific methods and
disciplines. Finally, 46 percent of risk assessors said they
participated in agencywide training. According to an EPA official, the
agency offers a broad array of agencywide risk assessment training. For
example, EPA's Risk Assessment Forum develops training to accompany the
agency's risk assessment guidelines. More specifically, forum staff
conducted briefings and orientation sessions on the 2005 cancer risk
assessment guidelines. In addition, the forum sponsors colloquia
approximately twice a year for staff to exchange information on risk
assessment issues. Recent colloquia dealt with dermal exposure
assessment and whether additional guidance is needed on the use of
Monte Carlo analysis. Colloquia usually result in reports that
summarize the findings and may inform future guidance documents.
Additional Training Is Needed:
While risk assessors reported taking advantage of and benefiting from
various forms of training, they also said additional training would
improve their ability to prepare risk assessments, a belief echoed by
agency officials we spoke with. Over 70 percent of risk assessors
stated that more in-depth or relevant training would improve their
ability to prepare risk assessments. More specifically, some risk
assessors expressed the need for training on analytic tools, such as
modeling the dose-response relationship and statistical analysis and
software. Several risk assessors also expressed a strong interest in
training on scientific topics, including toxicology and such emerging
issues as genomics, as well as nonscientific topics, such as public
communications and public relations. Some risk assessors suggested EPA
provide formal, comprehensive training for new risk assessors to
educate them on how to use the guidance documents and more advanced
courses for experienced risk assessors. Furthermore, many risk
assessors reported that more time (69 percent) and more funds (65
percent) for training would moderately or greatly improve their ability
to prepare risk assessments. (See fig. 6.)
Figure 7: Modifications in Training That Would Moderately or Greatly
Improve the Preparation of Risk Assessments:
[See PDF for image]
Source: GAO analysis of survey data.
[End of figure]
In addition to our survey respondents, some program officials we
interviewed pointed out the need for additional training for both risk
assessors and risk managers. For example, risk assessors need training
in emerging issues, such as genomics, so that they can use these types
of data in risk assessments, according to one agency official. In
contrast, risk managers need training on the elements of risk
assessment, so that they will be better able to interpret the
information provided and apply it to risk management decisions.
According to one program manager, risk managers often want the "bottom
line" (numerical) results of a risk assessment without understanding
the nature of the uncertainties in the assessment, or the potential
value of obtaining more information to help clarify those
uncertainties.
Finally, the changing nature of the workforce may have implications for
training at EPA. According to an agency official, many experienced risk
assessors who possess years of institutional knowledge are retiring or
nearing retirement age. Consequently, the agency needs to educate newer
risk assessment staff as quickly and thoroughly as possible to help
ensure that the agency's ability to accurately and effectively produce
risk assessments does not decline. While recently hired risk assessors
come to EPA with specialized knowledge in fields related to risk
assessment, they may not understand the broader context of risk
assessment. For example, a new employee with degrees in biology and
toxicology may not know how to integrate that knowledge with other
scientific information to prepare a risk assessment. Furthermore, one
EPA official noted that the agency has no formal training course, or
set of courses, to help develop staff's ability to prepare risk
assessments.
Enhanced Risk Assessment Planning, Improved Analysis and Review, and
Added Training Could Further Improve EPA's Process, but Barriers Could
Limit Progress:
The experts we spoke with, including representatives of federal and
state agencies, regulated industry, environmental advocacy groups, and
outside researchers and consultants, said the modifications EPA has
made over the past 10 years have been beneficial overall. However, they
identified additional actions EPA could take to improve its risk
assessment process, recognizing that EPA would face barriers to doing
so. Specifically, EPA could improve its planning process of what will
be required to complete a risk assessment by better identifying the
scientific data it has and data it needs on the potential adverse
effects from exposure to a contaminant and by seeking stakeholder input
early in this planning process. In addition, EPA could more thoroughly
evaluate methods and models, transparently document its analytic
choices, and enhance internal review. Finally, experts believe EPA
could provide additional training for risk assessors, managers, and
stakeholders. While these efforts would further improve the risk
assessment process, EPA could face barriers in carrying them out, such
as the scientific complexity of risk assessment, the difficulty of
obtaining and applying data, and a cultural resistance to deviating
from established methods.
Enhance Planning by Increasing Focus on Data Needs and Involving a
Broad Range of Stakeholders:
In order to ensure that EPA has the data needed for risk assessment, it
needs to better identify data that are available, prioritize its data
needs, and collaborate with the external research community during the
planning phase. For example, several experts said EPA should generate a
searchable database of studies conducted by different agencies and
organizations related to the chemicals being evaluated, so that
researchers and risk assessors could more easily identify what studies
are available and what additional research is needed. Experts also
suggested several ways for EPA to prioritize its data needs. For
example, sensitivity analysis can be used within individual risk
assessments to determine which data gaps are the most critical to the
risk assessment result. Some experts also said EPA could better
prioritize its data needs by increasing its use of data on the amounts
of contaminants in people's bodies to help concentrate its research on
the chemicals to which humans are actually exposed. Finally, several
experts suggested that EPA increase its collaboration with external
researchers, in part because the agency lacks the resources to
independently generate all of the data that are needed. If EPA more
effectively collaborated with other federal research organizations,
such as the National Toxicology Program and the National Institute of
Environmental Health Sciences, federal research dollars could be better
harnessed to help EPA protect the public from exposure to contaminants.
For example, the National Toxicology Program has the technology to
assist the Office of Pesticide Programs with its screening of inert
ingredients, which are all of the "other" chemicals in a pesticide
product. In addition, experts said EPA should use all relevant data,
including data from industry research laboratories, provided EPA takes
steps to ensure the data are generated in an unbiased and
scientifically defensible way. For example, experts suggested that EPA
could subject studies to independent peer review and evaluate the
sufficiency of data produced by these organizations to increase
confidence about using these data in EPA risk assessments.
Experts also said that EPA could improve the quality of risk
assessments if the agency enhanced its planning by more consistently
involving stakeholders, especially early in the process. Several
experts said that increased involvement with a broad range of
stakeholders early in the planning process would help identify
alternate methods and models to use and obtain stakeholder concurrence
with the agency's approach. Although all stakeholders might not agree
on the methods chosen, some experts believe that by seeking stakeholder
input on these issues early in the process, EPA may minimize arguments
later. In addition to stakeholder involvement with early planning,
several experts recommended that EPA increase coordination with
stakeholders throughout the process. For example, one expert said EPA
could more transparently acknowledge and address comments from the
public and other stakeholders, regardless of whether the agency planned
to implement their suggestions.
More Thoroughly Evaluate and Transparently Document Analytic Choices,
and Increase Internal Review:
EPA could more thoroughly evaluate its analytic choices and incorporate
or develop a wider variety of analytic tools. Some experts said that,
with regard to EPA's use of default options, risk assessors should more
thoroughly document why available data are insufficient to allow EPA to
use another analytic approach and commented that the revised cancer
guidelines may provide a useful framework for making this decision.
Furthermore, several experts said EPA could use a tool like sensitivity
analysis to assess and clearly communicate the extent to which the
choice of a method or default assumption affects the risk assessment
outcome. For example, if sensitivity analysis demonstrated that the
impacts were significant, EPA could use the analysis to identify the
critical areas where additional studies might reduce the need to rely
on a default assumption for that assessment. One expert pointed out
that the Office of Pesticide Programs uses sensitivity analysis in its
exposure assessments to estimate which uses of a pesticide present the
greatest risk to workers and how to mitigate those risks. In addition,
several experts recommended that EPA make better use of existing
analytic tools and develop new ones, where needed. For example, some
experts said EPA should more frequently employ probabilistic analyses
in risk assessments and incorporate the latest scientific tools, such
as genomics and computational toxicology, to better assess uncertainty
and variability. In addition, several experts noted that EPA needs to
develop tools and methodologies to better analyze certain aspects of
risk assessment, such as the combined effects of exposure to multiple
chemicals through multiple pathways.
Experts also said EPA risk assessments should clearly describe the
sufficiency of the data and the scientific basis for its choice of a
default assumption, method, or model. Some experts pointed out that
risk assessments should identify and clearly discuss any data that are
not available for the analysis, including the form the data need to be
in and the most appropriate study design or methodology to obtain the
needed data. In addition, several experts said EPA needs to more
explicitly communicate which default assumptions were used in a risk
assessment and why the defaults were chosen. For example, one expert
said that even though a risk assessment may be perfect, if the public
does not understand the rationale behind the agency's choices, the risk
assessment might be seen as flawed. Furthermore, in individual risk
assessments, the agency could more transparently identify which
critical studies would help the agency avoid relying on default
assumptions. Some experts also suggested that EPA use as case studies
completed assessments for which the agency had sufficient data to use
models and other analytic tools rather than default assumptions to more
accurately assess risks. Finally, some experts said that EPA should
more transparently consider alternate methods and models in each risk
assessment. For example, EPA should be more transparent about the
judgments it makes when it employs certain methods, such as the
benchmark dose method, which identifies the dose that produces a small
increase in the risk of an adverse effect.
Finally, experts suggested that EPA increase internal reviews of risk
assessments by staff members with extensive risk assessment experience.
Internal reviews could improve the risk assessment process in two ways:
first, to assure the quality of risk assessments and second, to ensure
that the design of its risk assessments match the needs of risk
managers. For example, one expert suggested EPA reinstate a senior peer
review group, composed of experienced risk assessors from throughout
the agency. Others suggested that EPA could also internally peer review
risk assessments prepared by less experienced staff to ensure that
default assumptions are applied appropriately and transparently
explained. In addition to increased review of individual risk
assessments, some experts also felt the risk assessment process could
benefit from additional examination of agencywide cross-cutting issues
applicable to all program offices. For example, one expert said that
some analytic tools, such as Monte Carlo analysis, were not developed
specifically for use in risk assessments and suggested that EPA work
with ORD's National Center for Computational Toxicology to define how
these tools could be used in risk assessments across EPA. Moreover,
according to several experts, agencywide discussions and activities
promote consistency in risk assessment practices. For example, some
experts thought EPA could benefit from a systematic agencywide
discussion of the sources of uncertainty in risk assessment.
More Training Could Improve Risk Assessor, Risk Manager, and
Stakeholder Understanding of the Process:
Experts emphasized the importance of training for risk assessors, risk
managers, and the stakeholder community on all elements of the risk
assessment process. Several experts said risk assessors are not
adequately trained in basic risk assessment principles, such as
available default assumptions and when they should be used or replaced.
Some experts also suggested risk assessors receive training in using
and applying models and in how to interpret data from emerging
scientific fields to improve their ability to use these data, as
appropriate, in risk assessments. Several experts also believe that
training for risk managers would help improve risk assessments because
risk managers need to better understand the role risk assessment plays
in risk management. According to some experts, risk managers who are
more familiar with the process are better equipped to support risk
assessors and ensure that the risk assessment considers all appropriate
factors. Finally, a few experts also suggested that EPA hold training
for stakeholders in the risk assessment process. For example, one
expert suggested that EPA develop Web-based training for both the
regulated community and regulators themselves to help ensure
consistency in how they understand the process. As part of this
training, EPA could explain how risk assessment fits into the overall
risk management process.
EPA Faces Barriers to Improving Its Risk Assessment Process, Such as
the Complexity of Risk Assessment, Difficulty of Acquiring and Applying
Data, and a Culture Resistant to Change:
While experts identified a number of actions EPA could take to improve
the risk assessment process, they said EPA may face barriers such as
the highly complex, technical, and time-intensive nature of preparing
risk assessments, challenges in acquiring and applying data from all
available sources, and a general reluctance to deviate from its
established methods and assumptions. Several experts pointed out that
EPA's risk assessments have grown more technically challenging and
require risk assessors and managers to possess different skills than in
the past. For example, some experts told us risk managers have
different levels of expertise and background in risk assessment, and
may not fully understand how risk assessment helps inform regulatory
decisions. Moreover, some experts said that because risk assessment is
just one piece of information used to make a regulatory decision, it is
difficult to explain to stakeholders and the public the impact of risk
assessments on risk management decisions. Experts also pointed out that
scientific knowledge on subjects, such as uncertainty and variability,
is limited and analytic tools are still being developed. For example,
several experts said that while it would be useful for EPA to more
fully consider the risks of exposure to a single chemical from all
exposure pathways, at present it is an emerging science with few well
developed analytic tools to use in risk assessments. In addition, using
tools, such as probabilistic analysis, to assess variability requires
large amounts of data that are seldom available. Finally, several
experts said that improving the process by such steps as incorporating
new analytic techniques and conducting thorough internal review
requires more time and coordination. For example, one expert pointed
out that EPA does not always have the staff and time to analyze all
sets of data or to examine alternative methods or models that might
provide a more robust risk estimate.
In addition to barriers attributable to the complexity of preparing
risk assessments, experts also said EPA may face barriers in acquiring
and applying data from all available sources. Many experts commented
that data are expensive to obtain, and EPA has limited financial
resources to devote to such activities. For example, some experts
pointed out that some of the more direct studies of human exposure,
such as epidemiological or biomonitoring studies, are quite expensive
to conduct. Furthermore, EPA may be reluctant to use available data
from all sources. As several experts pointed out, data from industry-
sponsored researchers might be perceived as biased, potentially
subjecting EPA to criticism. Despite potential perceptions of bias,
some experts thought EPA should have the ability to use all available
data, regardless of its source, as long as the data in question have
been appropriately peer reviewed. In addition, some experts said
statutory requirements may limit EPA's ability to use certain data. For
example, the Toxic Substances Control Act limits EPA's authority to
require extensive data from industry before deciding whether to approve
a new chemical. Some experts also pointed out that research does not
always produce clear-cut results. For example, one expert commented
that epidemiological studies of the general population may not account
for confounding factors, such as exposure to other chemicals, which
complicate efforts to draw conclusions about the effects of a single
chemical. In addition, some experts said that variability, an important
but scientifically complicated issue, often creates inconsistencies
across studies because many factors such as geography, lifestyle, and
food intake affect an individual's response.
Finally, experts said that EPA has a general reluctance to deviate from
using methods and assumptions it has used in the past. As a result,
experts said EPA prefers to use techniques that have been generally
accepted in the scientific community than to use methods that rely on
recent scientific advances. For example, some experts told us EPA is
often reluctant to deviate from its established default assumptions.
Furthermore, some experts also commented that risk assessors may not
have an incentive to deviate from methods and assumptions they have
used in the past because it may make the risk assessment more easily
challenged by those who disagree with it. In addition, some experts
said the level of comfort in using new methods varies throughout the
agency. For example, one expert believes that probabilistic models have
been applied inconsistently because some risk assessors have been
unwilling to deviate from the standard models.
Conclusions:
While technical and difficult to understand by nature, risk assessment
is a key element in EPA's efforts to protect human health from the
potentially harmful effects of chemicals, pollutants, and toxic
substances that people encounter in their everyday lives. Since 1994,
EPA has taken a number of steps, including greater involvement by the
public and other stakeholders, to strengthen and improve its process
for preparing assessments of the risks posed by contaminants in the
environment. Independent reviewers as well as the experts and EPA risk
assessors we contacted said overall EPA's efforts have improved the
agency's risk assessments. However, the agency itself and the
individuals we contacted acknowledge that EPA needs to do more. While
some barriers to further improvement depend on scientific advances that
are largely beyond EPA's control, other actions to improve its risk
assessment process are within its control. Specifically, when EPA
engages the stakeholder and research communities after the risk
assessment has largely been completed, it misses opportunities to
benefit from their expertise. By working with stakeholders early and
periodically throughout the process to identify key issues, studies,
methods, and default assumptions that need to be considered in the
analysis, EPA would help ensure consistent, transparent, and high-
quality risk assessments. On the other hand, failure to take full
advantage of stakeholders' knowledge and points of view is likely to
contribute to the perception among stakeholders that their concerns are
not adequately represented in the risk assessments and that EPA's
decisions lack transparency. While EPA has issued a number of guidance
and policy documents advocating the benefits of early planning, it
acknowledges it could do more to ensure that such planning and
consultation take place and involve relevant stakeholders. Furthermore,
EPA does not always systematically communicate its data needs to the
research community. While EPA has begun to better identify and
prioritize its specific data needs, it has not been able to
consistently develop data it needs in a timely manner. A more proactive
approach to communicating its research needs to outside public and
private researchers would help EPA more efficiently use the limited
resources it has to obtain the data it needs. Furthermore, this
approach would increase the likelihood that EPA would have data it
needs to complete risk assessments now and into the future and that
appropriately designed research projects would be conducted.
Transparently communicating its research needs would also enhance EPA's
ability to produce high-quality, scientifically defensible risk
assessments and reduce the uncertainty associated with the effects of
many contaminants on human health. Although experts we interviewed said
EPA may hesitate to seek and use data from a wide range of sources
because it could be seen as biased, EPA could take steps to ensure the
quality of data generated by others. By doing so, EPA would expand its
cache of available data and, potentially, reduce its reliance on
default assumptions. Finally, current workforce models of high-
performing organizations stress the need to formally and
comprehensively assess the skill and competency requirements for staff
and to identify related training and developmental needs to ensure that
the workforce retains a high level of needed skills. In recent years,
EPA's emphasis on training for its risk assessors and managers has
declined in the areas risk assessors and experts say are needed to
improve the quality of risk assessments and take advantage of recent
scientific and analytic advances. Without an agencywide training
program for its risk assessment and risk management workforce, the
quality, consistency, and transparency of risk assessments and risk
management decisions will likely continue to be challenged by
stakeholders and the public.
Recommendations for Executive Action:
To improve the overall quality, consistency, and transparency of its
risk assessments, we recommend that the Administrator of EPA direct the
appropriate agency entities to take the following three actions:
* Develop a strategy to ensure that offices engage in early planning to
identify and seek the expertise needed, both within the EPA workforce
and from external subject matter experts. The strategy should delineate
such things as how EPA could use the available expertise to determine
the needed data, the relevant default assumptions, the extent of
internal and external review that needs to be included in the
assessment, and the approach used to consistently involve a broad range
of stakeholders--including the public, regulated industry, federal
agencies, and advocacy groups--as appropriate to the risk assessment.
* More proactively identify the data most relevant to the current risk
assessment needs, including the specific studies required and how those
studies should be designed, and communicate those needs to the research
community. Increased collaboration among program offices in identifying
needed data would help ensure that the resulting data will meet the
needs of multiple offices. In addition, EPA should better communicate
these data needs and better coordinate research planning with the
external public and private research community to help focus EPA's
limited resources.
* Ensure that risk assessors and risk managers have the skills needed
to produce quality risk assessments by developing and implementing in-
depth training. This training should address the needs of risk
assessors and managers with varying levels of expertise by including
basic courses, such as an overview of risk assessment, as well as more
advanced courses on topics such as modeling, toxicology, and other
advanced scientific techniques.
Agency Comments:
We provided EPA with a draft of this report for review and comment. EPA
neither agreed nor disagreed with our findings and recommendations.
However, the agency provided specific comments to improve the report's
technical accuracy, which we incorporated as appropriate.
As agreed with your office, unless you publicly announce the contents
of this report earlier, we plan no further distribution until 30 days
from the report date. At that time, we will send copies to the
Administrator, EPA, as well as to appropriate congressional committees,
and other interested Members of Congress. We also will make copies
available to others upon request. In addition, the report will be
available at no charge on the GAO Web site at [Hyperlink,
http://www.gao/gov].
If you or your staff have questions about this report, please contact
me at (202) 512-6225 or stephensonj@gao.gov. Contact points for our
Offices of Congressional Relations and Public Affairs may be found on
the last page of this report. GAO staff who made key contributions to
this report are listed in appendix II.
Sincerely yours,
Signed by:
John B. Stephenson:
Director, Natural Resources and Environment:
[End of section]
Appendix I: Objectives, Scope, and Methods:
Our objectives for this review were to (1) identify the significant
recommendations to improve human health risk assessment that have been
made since 1994; (2) describe what the Environmental Protection Agency
(EPA) has done to modify its human health risk assessment process over
the same period; (3) determine the effects these past modifications
have had on the preparation of risk assessments; and (4) identify any
additional actions experts believe EPA could take to improve its risk
assessment process in the future, and the barriers EPA would face in
doing so.
To identify significant recommendations to improve human health risk
assessment since 1994, we reviewed EPA documents, including those
produced by EPA's Risk Assessment Forum (RAF), Science Policy Council
(SPC), Council for Regulatory Environmental Modeling (CREM), and
Science Advisory Board (SAB) as well as each of EPA's program offices.
We also reviewed our own reports and documents produced by the National
Academy of Sciences and the Presidential/Congressional Commission on
Risk Assessment and Risk Management. To gain an external perspective,
we spoke with experts in the risk assessment field, who identified many
of these documents in the course of our discussions and provided
insight into some of the documents' recommendations.
To describe what EPA has done to modify its human health risk
assessment process, we interviewed program office managers from the
Office of Air and Radiation (OAR), Office of Pesticide Programs (OPP),
Office of Pollution Prevention and Toxics (OPPT), Office of Water (OW),
and Office of Research and Development (ORD). We did not include the
site-specific risk assessment activities of the Office of Solid Waste
and Emergency Response in our review. Within ORD, we interviewed
managers in two of EPA's laboratories (the National Health and
Environmental Effects Laboratory and the National Exposure Research
Laboratory) and three of EPA's research centers (the National Center
for Environmental Assessment, National Center for Environmental
Research, and National Center for Computational Toxicology). We also
interviewed officials from RAF, SPC, CREM, SAB, and the Office of the
Science Advisor. Furthermore, we attended various EPA and stakeholder
group training sessions and meetings. Since we limited our review to
the human health aspects of risk assessment since 1994, our analysis
does not highlight EPA's modifications prior to 1994, including
publication of guidance documents that are highly relevant to risk
assessment practices, and does not address issues specifically related
to ecological risk assessment.
To assess the effects these modifications have had on the preparation
of risk assessments, we conducted a Web-based nonprobability survey of
all human health risk assessors from ORD and four EPA program offices
that conduct human health risk assessment (OAR, OPP, OPPT, and OW). We
used the survey to obtain an internal perspective on the usefulness of
many of the modifications EPA made since 1994, as well as on aspects of
EPA's risk assessment process, including guidance documents, training,
organizational structure, and collaboration. In developing the Web-
based questionnaire, we met with EPA officials from the five offices
surveyed to gain a thorough understanding of the risk assessment issues
specific to each office and identify the sampling frame. In order to
identify human health risk assessors--a label that is not an EPA job
series--we obtained from EPA officials in each program office being
reviewed the names of agency staff who worked on any part of the human
health risk assessment process since January 2001. Our sampling frame
consisted of 270 staff that met this criterion. This report does not
contain all the results from the survey. The survey and results can be
viewed at [Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-06-637SP].
The practical difficulties of conducting any survey may introduce
nonsampling error. For example, differences in how a particular
question is interpreted, the sources of information available to
respondents, or the types of people who do not respond can introduce
unwanted variability into the survey results. In order to reduce
nonsampling error, we pretested the questionnaire with five risk
assessors, one from each of the offices surveyed. During these
pretests, we asked agency officials to complete the survey as we
observed the process. We then interviewed the respondents to ensure
that (1) the questions were clear and unambiguous, (2) the terms used
were precise, (3) the questionnaire did not place an undue burden on
the agency officials completing it, and (4) the questionnaire was
independent and unbiased. On the basis of the feedback from the
pretests, we modified the questions, as appropriate. Information about
accessing the questionnaire was provided via e-mail for all survey
participants. The survey was activated, and staff informed of its
availability on October 17, 2005; it was available until January 13,
2006. To ensure security and data integrity, we provided all
participants with a personal password that allowed them to access and
complete a questionnaire. No one else could access that questionnaire
or edit its data. We included steps in both the data collection and
data analysis stages for the purpose of minimizing such nonsampling
errors. To reduce survey nonresponse, we sent e-mail reminders and
conducted follow-up telephone calls with nonrespondents. Overall, 82
percent of the 270 risk assessors in our sampling frame responded to
our survey, and all offices had a response rate of at least 80 percent.
We used general modifiers (i.e., many, several, some, a few, and a
couple) to characterize written responses to some open ended survey
questions. We used the following method to assign these modifiers to
our statements about risk assessor's survey responses: "many"
represents 22 to 44 respondents (roughly 10 to 20 percent), "several"
represents 12 to 21 respondents (5 to 10 percent), "some" represents 4
to 11 respondents, "a few" represents 3 respondents, and "a couple"
represents 2 respondents. These divisions do not represent technically
established categories; rather, we chose these divisions because they
aligned with natural breaks in response "themes" highlighted in the
report.
To assess further actions EPA could take to improve its risk assessment
process and to identify barriers it may face in doing so, we
interviewed experts representing a range of stakeholders in the
process. Specifically, we contacted risk assessment scientists;
toxicologists; scientific advisers to EPA; state officials; and
representatives from regulated industries, government agencies, and
environmental advocacy groups who have an expertise in risk assessment.
We used an iterative process (often referred to as the "snowball
sampling" technique) to identify these knowledgeable experts and
selected for interviews those who would provide us with a broad and
balanced range of perspectives on EPA risk assessment practices.
We first contacted the National Academy of Sciences' Board of
Environmental Studies and Toxicology, which is the academy's principal
study unit for environmental pollution problems affecting human health
and the assessment and management of related risks to human health and
the environment. We presented our engagement to the board and sought
its input on the areas in which EPA has made the most progress
improving its risk assessment practices and areas EPA will need to
focus on in the future. We also asked members if they would be willing
to participate in a future interview and solicited the names of other
experts who would be appropriate for us to contact about this
engagement. We selected for interviews experts who would provide us
with a broad and balanced range of perspectives on EPA risk assessment
practices. We continued interviewing and soliciting names until we
determined we had appropriate coverage from all the relevant
stakeholder groups. Our sampling identified 22 experts, listed
alphabetically, as follows: Elizabeth L. Anderson, Ph.D; Gail Charnley,
Ph.D; Harvey J. Clewell, M.A; Shannon Cunniff; Kerry Dearfield, Ph.D;
Michael L. Dourson, Ph.D; Elaine M. Faustman, Ph.D; Paul Gilman, Ph.D;
Gary Ginsberg, Ph.D; Sherri Goodman, Esq; Judith A. Graham, Ph.D; Dan
Greenbaum; Leslie J. Hushka, Ph.D; Annie M. Jarabek, B.S; James H.
Johnson, Ph.D; Elizabeth Julien, Ph.D; Dorothy Patton, Ph.D; Jonathan
M. Samet, Ph.D; Jennifer Sass, Ph.D; Chris Whipple, Ph.D; Richard
Wiles, M.A; and Lauren Zeise, Ph.D.
We used a standard set of questions to interview each of these experts
to ensure we consistently discussed each aspect of EPA risk assessment
policies and practices. To develop the questions, we reviewed
documentation on EPA's risk assessment process and reports prepared by
the National Academy of Sciences. We pretested our questions with two
of the experts and refined the questions accordingly. We used content
analysis to identify the main themes among their responses. In
addition, we asked the experts for their opinions about the many risk
assessment modifications EPA has made since 1994, and used content
analysis to synthesize their comments.
We conducted our work from February 2005 through March 2006 in
accordance with generally accepted government auditing standards.
[End of section]
Appendix II: GAO Contact and Staff Acknowledgments:
GAO Contact:
John B. Stephenson, (202) 512-6225 or stephensonj@gao.gov:
Staff Acknowledgments:
In addition to the contact named above, Cheryl Williams (Assistant
Director), Jennifer Cook, Michelle Cooper, Elizabeth Erdmann, and
Rebecca Shea made key contributions to this report. Also contributing
to this report were Nancy Crothers, Richard Frankel, and Roderick
Moore.
FOOTNOTES
[1] Although other regulatory agencies, such as the Food and Drug
Administration, also use risk assessments as part of regulatory
decision making, this report discusses only the risk assessment process
used by EPA.
[2] EPA's mission is to protect human health and to safeguard the
natural environment--air, water, and land--upon which life depends.
This report focuses only on EPA's efforts to protect human health.
[3] Pollutants are generally categorized as hazardous air pollutants
under the Clean Air Act if they cause or may cause cancer or other
serious health effects, such as reproductive effects or birth defects,
or adverse environmental and ecological effects. Currently, the Clean
Air Act regulates 187 chemicals and chemical categories as hazardous
air pollutants.
[4] National Academy of Sciences, Risk Assessment in the Federal
Government: Managing the Process (Washington, D.C., 1983).
[5] The Presidential/Congressional Commission was created by Pub. L.
No. 101-549 (1990).
[6] Peer review is a documented critical review of a specific
scientific or technical work product, conducted by qualified
individuals who are independent of those who performed the work, but
who are collectively equivalent in technical expertise--for example,
EPA's Science Advisory Board or the National Academy of Sciences.
According to EPA's 2006 Peer Review Policy, peer review can be
internal, in which the reviewers are independent experts from inside
EPA, or external, in which the reviewers are independent experts from
outside EPA.
[7] National Academy of Sciences, Science and Judgment in Risk
Assessment (Washington, D.C., 1994).
[8] National Academy of Sciences, Understanding Risk: Informing
Decision in a Democratic Society (Washington, D.C., 1996).
[9] National Academy of Sciences, Strengthening Science at the U.S.
Environmental Protection Agency (Washington, D.C., 2000).
[10] EPA's Science Advisory Board provides independent advice and peer
review on scientific and technical aspects of environmental problems
and issues. Experts, including scientists, engineers, and economists,
provide independent, balanced, and scientifically sound advice to EPA.
[11] IRIS contains information on the human health effects that may
result from exposure to various chemicals in the environment and helps
provide consistent information on chemical substances for use in risk
assessments.
[12] The Agency for Toxic Substances and Disease Registry is the
primary public health agency involved with hazardous waste issues and
works to prevent or reduce the harmful effects of exposure to hazardous
substances on human health by, for example, supporting research that
assists with risk assessment.
[13] Endocrine disrupting chemicals are thought to mimic natural human
hormones that influence important regulatory and development mechanisms
such as blood pressure, metabolism, and reproduction. Important
endocrine glands include the thyroid, pancreas, and male and female
gonads (testes and ovaries).
[14] The STAR program funds peer reviewed competitive grants on
research topics selected by ORD and postgraduate training for
scientists in environmental fields.
[15] EPA's defaults represent a choice that, although scientifically
plausible given the existing uncertainty, is more likely to result in
overestimating than underestimating human health risk.
[16] Contaminants can progressively accumulate in the tissues of an
organism, such as a human or a fish, as a result of uptake by the body
from all routes of exposure. This process, called bioaccumulation,
occurs because the rate of intake exceeds the organism's ability to
eliminate the substance from the body.
[17] Neurotoxicity is an adverse change in the structure or function of
the central or peripheral nervous system following exposure to a
chemical, physical, or biological agent.
[18] U.S. Environmental Protection Agency, Peer Review Handbook
(Washington, D.C., 2000).
[19] ORD's laboratories and centers are the National Center for
Environmental Assessment (NCEA), National Health and Environmental
Effects Research Laboratory (NHEERL), National Exposure Research
Laboratory (NERL), National Center for Environmental Research (NCER),
National Risk Management Research Laboratory (NRMRL), and National
Homeland Security Research Center.
[20] U.S. Environmental Protection Agency, Risk Assessment Principles
and Practice (Washington, D.C., 2004).
[21] U.S. Environmental Protection Agency, Guidance on Cumulative Risk
Assessment--Part 1: Planning and Scoping (Washington, D.C., 1997).
[22] U.S. Environmental Protection Agency, Lessons Learned on Planning
and Scoping for Environmental Risk Assessments (Washington, D.C.,
2002).
[23] These six principal pollutants, known as "criteria pollutants,"
are carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter,
and sulfur dioxide.
[24] EPA is reviewing older pesticides (those initially registered
prior to November 1984) under the Federal Insecticide, Fungicide, and
Rodenticide Act to ensure they meet current scientific and regulatory
standards. EPA is also reassessing tolerances (pesticide residue limits
in food) to ensure they meet safety standards established under the
Food Quality Protection Act (FQPA) of 1996. Under FQPA, EPA must
reassess all tolerances established before August 3, 1996, within 10
years. The Office of Pesticide Programs reviews the registrations of
all pesticide products every 15 years to determine whether they still
meet safety standards as part of its registration review process.
[25] Office of Management and Budget, Guidelines for Ensuring and
Maximizing the Quality, Objectivity, Utility, and Integrity of
Information Disseminated by Federal Agencies (Washington, D.C., 2002).
[26] U.S. Environmental Protection Agency, A Summary of General
Assessment Factors for Evaluating the Quality of Scientific and
Technical Information (Washington, D.C., 2003).
[27] In September 2002, EPA formed the National Homeland Security
Research Center to, among other things, provide appropriate,
affordable, effective, and validated technologies and methods for
assessing risks posed by chemical, biological, and radiological terror
attacks.
[28] To comply with the Government Performance and Results Act (GPRA),
EPA every 3 years generates an agencywide 5-year strategic plan that
highlights high-level environmental issues. The most recent plan for
fiscal years 2003-2008 identified key research needs related to EPA's
mission.
[29] The four strategic research directions are harmonizing cancer and
noncancer risk assessments, assessing aggregate and cumulative risk,
determining risk to susceptible human subpopulations, and conducting
research to enable evaluation of public health outcomes from risk
management decisions.
[30] The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), 7
U.S.C. §§ 136-136y.
[31] Applicants must submit data on the acute and chronic toxicity of
the pesticide product under different conditions, such as how and at
what rate it can be applied. See 40 C.F.R. Part 158 (2005).
[32] ILSI-RSI is primarily funded through cooperative agreements with
regulatory agencies such as EPA and Health Canada, but also receives
financial support from the European Commission, the National Institute
of Environmental Health Sciences, and industry trade groups.
[33] EPA uses four criteria to prioritize chemicals for IRIS reviews:
(1) EPA statutory, regulatory, or program needs; (2) availability of
new scientific information that might significantly change the current
information; (3) interest from state and local government or the
public; and (4) the amount of additional information that would be
needed to complete the review. Ultimately, the decision to assess any
given substance hinges on available agency resources.
[34] The Air Toxics Risk Assessment Reference Library is a multivolume
technical resource manual that provides information on the fundamental
principles of risk-based assessment for hazardous air pollutants and
how to apply those principles in different settings.
[35] U.S. Environmental Protection Agency, Report of the Agency Task
Force on Environmental Regulatory Modeling--Guidance, Support Needs,
Draft Criteria and Charter (Washington, D.C., 1994).
[36] U.S. Environmental Protection Agency, Model Validation for
Predictive Exposure Assessments (Washington, D.C., 1994).
[37] U.S. Environmental Protection Agency, Draft Guidance on the
Development, Evaluation, and Application of Regulatory Environmental
Models (Washington, D.C., 2003).
[38] U.S. Environmental Protection Agency, Policy for Use of
Probabilistic Analysis in Risk Assessment (Washington, D.C., 2003).
[39] U.S. Environmental Protection Agency, Children's Total Exposure to
Persistent Pesticides and Other Persistent Organic Pollutants
(Washington, D.C., 1999).
[40] Exec. Order No. 13045, 62 Fed. Reg. 19885 (Apr. 21, 1997).
[41] U.S. Environmental Protection Agency, Review of the Reference Dose
and Reference Concentration Processes (Washington, D.C., 2002).
[42] U.S. Environmental Protection Agency, Supplementary Guidance for
Conducting Health Risk Assessment of Chemical Mixtures (Washington,
D.C., 2000).
[43] U.S. Environmental Protection Agency, Framework for Cumulative
Risk Assessment (Washington, D.C., 2003).
[44] See § 405 of the Food Quality Protection Act of 1996, amending 21
U.S.C. § 346a(b)(2)(D)(vi).
[45] U.S. Environmental Protection Agency, General Principles for
Performing Aggregate Exposure and Risk Assessments (Washington, D.C.,
2001).
[46] U.S. Environmental Protection Agency, Guidance on Cumulative Risk
Assessment of Pesticide Chemicals That Have a Common Mechanism of
Toxicity (Washington, D.C., 2002).
[47] For example, metals released into the air may be deposited on the
ground, where they remain in surface soils for long periods of time.
The chemicals in the soil may be taken up into plants through the roots
and accumulate in the tissues of foraging animals.
[48] By statute, hazardous air pollutants are regulated not as
individual pollutants but by emission sources that consist of a group
of similar industrial processes or industries that release multiple
pollutants.
[49] Guidelines refer to the Guidelines for Carcinogen Risk Assessment,
Guidelines for Neurotoxicity Risk Assessment, Guidelines for
Reproductive Toxicity Risk Assessment, and Supplemental Guidelines for
Chemical Mixtures. Reference documents refer to the Assessment Factors
Handbook, Exposure Factors Handbook, Framework for Cumulative Risk
Assessment, Guiding Principles for Monte Carlo Analysis, Peer Review
Handbook, Review of Reference Dose and Reference Concentration
Processes, Risk Assessment Principles and Practices, and Risk
Characterization Handbook. Policy documents refer to the Policy on
Evaluating Health Risks to Children, Policy for Use of Probabilistic
Analysis in Risk Assessment, Interim Genomics Policy, and Interim
Position on Environmental Endocrine Disruption.
[50] The National Toxicology Program is an interagency program
established by the Department of Health and Human Services that
provides information about potentially toxic chemicals to health,
regulatory, and research agencies, scientific and medical communities,
and the public.
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