Aviation Safety
More Research Needed on the Effects of Air Quality on Airliner Cabin Occupants Gao ID: GAO-04-54 January 16, 2004Over the years, the traveling public, flight attendants, and the medical community have raised questions about how airliner cabin air quality contributes to health effects, such as upper respiratory infections. Interest in cabin air quality grew in 2003 when a small number of severe acute respiratory syndrome (SARS) infections may have occurred on board aircraft serving areas that were experiencing outbreaks of the disease. In 2001, a National Research Council report on airliner cabin air quality and associated health effects recommended that additional research be done on the potential health effects of cabin air. GAO reviewed what is known about the health effects of cabin air, the status of actions recommended in the 2001 National Research Council report, and whether available technologies should be required to improve cabin air quality.
Despite a number of studies of the air contaminants that airline passengers and flight attendants are potentially exposed to, little is known about their associated health effects. Reports on airliner cabin air quality published by the National Research Council in 1986 and 2001 concluded that more research was needed to determine the nature and extent of health effects on passengers and cabin crew. Although significant improvements have been made to aircraft ventilation systems, cabin occupants are still exposed to allergens and infectious agents, airflow rates that are lower than those in buildings, and air pressures and humidity levels that are lower than those normally present at or near sea level. The 2001 National Research Council report on airliner cabin air quality made 10 recommendations, 9 of which directed the Federal Aviation Administration (FAA) to collect more data on the potential health effects of cabin air and to review the adequacy of its standards for cabin air quality. FAA has addressed these 9 recommendations to varying degrees as it attempts to balance the need for more research on cabin air with other research priorities (e.g., passenger safety). However, some in the aviation community, including some of the committee members who produced the report on cabin air, do not feel that FAA's planned actions will address these recommendations adequately. For example, most members were concerned that FAA's plan for implementing the report's key recommendations on the need for more comprehensive research on the health effects of cabin air was too limited. FAA plans to address these recommendations in two parts--the first, which started in December 2003, and the second, which will start in December 2004 and end in late 2006 or early 2007. However, FAA lacks a comprehensive plan, including key milestones and funding needs. In addition, most committee members thought that FAA's response to a recommendation for it to improve public access to information on the health risks of flying was inadequate. We also had difficulty accessing this information on FAA's Web site. Several technologies are available today that could improve cabin air quality, (e.g., increasing cabin humidity and pressure or absorbing more cabin odors and gasses); however, opinions vary on whether FAA should require aircraft manufacturers and airlines to use these technologies. GAO found that one available technology, high-efficiency particulate air (HEPA) filtering, was strongly endorsed by cabin air quality and health experts as the best way to protect cabin occupants' health from viruses and bacteria in recirculated cabin air. While FAA does not require the use of these filters, GAO's survey of major U.S. air carriers found that 85 percent of large commercial airliners in their fleets that recirculate cabin air and carry more than 100 passengers already use these filters. However, the use of HEPA filters in smaller commercial aircraft that carry fewer than 100 passengers is much lower. The cost to retrofit the smaller aircraft to accept the HEPA filter, if it were made mandatory, could be expensive.
RecommendationsOur recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.
Director: Team: Phone:GAO-04-54, Aviation Safety: More Research Needed on the Effects of Air Quality on Airliner Cabin Occupants
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Report to the Ranking Democratic Member, Subcommittee on Aviation,
Committee on Transportation and Infrastructure, House of
Representatives:
January 2004:
AVIATION SAFETY:
More Research Needed on the Effects of Air Quality on Airliner Cabin
Occupants:
GAO-04-54:
GAO Highlights:
Highlights of GAO-04-54, a report to the Ranking Democratic Member,
Subcommittee on Aviation, Committee on Transportation and
Infrastructure, House of Representatives
Why GAO Did This Study:
Over the years, the traveling public, flight attendants, and the
medical community have raised questions about how airliner cabin air
quality contributes to health effects, such as upper respiratory
infections. Interest in cabin air quality grew in 2003 when a small
number of severe acute respiratory syndrome (SARS) infections may have
occurred on board aircraft serving areas that were experiencing
outbreaks of the disease. In 2001, a National Research Council report
on airliner cabin air quality and associated health effects
recommended that additional research be done on the potential health
effects of cabin air.
GAO reviewed what is known about the health effects of cabin air, the
status of actions recommended in the 2001 National Research Council
report, and whether available technologies should be required to
improve cabin air quality.
What GAO Found:
Despite a number of studies of the air contaminants that airline
passengers and flight attendants are potentially exposed to, little is
known about their associated health effects. Reports on airliner cabin
air quality published by the National Research Council in 1986 and
2001 concluded that more research was needed to determine the nature
and extent of health effects on passengers and cabin crew. Although
significant improvements have been made to aircraft ventilation
systems, cabin occupants are still exposed to allergens and infectious
agents, airflow rates that are lower than those in buildings, and air
pressures and humidity levels that are lower than those normally
present at or near sea level.
The 2001 National Research Council report on airliner cabin air
quality made 10 recommendations, 9 of which directed the Federal
Aviation Administration (FAA) to collect more data on the potential
health effects of cabin air and to review the adequacy of its
standards for cabin air quality. FAA has addressed these 9
recommendations to varying degrees as it attempts to balance the need
for more research on cabin air with other research priorities (e.g.,
passenger safety). However, some in the aviation community, including
some of the committee members who produced the report on cabin air, do
not feel that FAA‘s planned actions will address these recommendations
adequately. For example, most members were concerned that FAA‘s plan
for implementing the report‘s key recommendations on the need for more
comprehensive research on the health effects of cabin air was too
limited. FAA plans to address these recommendations in two parts”the
first, which started in December 2003, and the second, which will
start in December 2004 and end in late 2006 or early 2007. However,
FAA lacks a comprehensive plan, including key milestones and funding
needs. In addition, most committee members thought that FAA‘s response
to a recommendation for it to improve public access to information on
the health risks of flying was inadequate. We also had difficulty
accessing this information on FAA‘s Web site.
Several technologies are available today that could improve cabin air
quality, (e.g., increasing cabin humidity and pressure or absorbing
more cabin odors and gasses); however, opinions vary on whether FAA
should require aircraft manufacturers and airlines to use these
technologies. GAO found that one available technology, high-efficiency
particulate air (HEPA) filtering, was strongly endorsed by cabin air
quality and health experts as the best way to protect cabin occupants'
health from viruses and bacteria in recirculated cabin air. While FAA
does not require the use of these filters, GAO‘s survey of major U.S.
air carriers found that 85 percent of large commercial airliners in
their fleets that recirculate cabin air and carry more than 100
passengers already use these filters. However, the use of HEPA filters
in smaller commercial aircraft that carry fewer than 100 passengers is
much lower. The cost to retrofit the smaller aircraft to accept the
HEPA filter, if it were made mandatory, could be expensive.
What GAO Recommends:
GAO recommends that FAA develop detailed plans for its research and
surveillance program on cabin air quality, improve the public‘s access
to information on the health risks of flying, and assess the costs and
benefits of requiring HEPA filters in commercial aircraft.
www.gao.gov/cgi-bin/getrpt?GAO-04-54.
To view the full product, including the scope and methodology, click
on the link above. For more information, contact Gerald L. Dillingham
at (202) 512-2834 or dillinghamg@gao.gov.
[End of section]
Contents:
Letter:
Results in Brief:
Background:
Despite a Number of Studies, Data Are Lacking About the Effects of Air
Quality On Cabin Occupants:
FAA has Taken Action to Address Council Recommendations On Cabin Air
Quality, but These Efforts Could Be Improved:
Some Technologies Exist for Improving Cabin Air Quality, but There Are
Questions About Whether They Should be Required:
Conclusions:
Recommendations for Executive Action:
Agency Comments:
Appendixes:
Appendix I: Objectives, Scope, and Methodology:
Appendix II: Biographical Information on the National Research Council
Committee:
Appendix III: Transmission of Severe Acute Respiratory Syndrome (SARS)
on Board Aircraft Is Rare and Associated with Proximity:
Appendix IV: European CabinAir Study: Scope and Methodology:
Appendix V: Surveillance and Research Programs:
Surveillance Program:
Research Program:
Appendix VI: GAO Contacts and Staff Acknowledgments:
GAO Contacts:
Staff Acknowledgments:
Selected Bibliography:
Tables:
Table 1: Potential Air Quality Related Concerns on Aircraft Cited by
the National Research Council in 2001:
Table 2: Status of the National Research Council's 2001 Report
Recommendations on Airliner Cabin Air Quality:
Table 3: Number of Large and Regional Aircraft of Top 28 Airlines That
Do or Do Not Recycle Cabin Air:
Figures:
Figure 1: Passenger Cabin of Commercial Airliner:
Figure 2: Overview of How Air Is Supplied on a Commercial Airliner:
Figure 3: A Typical HEPA Filter for Commercial Passenger Aircraft:
Abbreviations:
AFA: Association of Flight Attendants:
APFA: Association of Professional Flight Attendants:
APL: Applied Physics Laboratory (Johns Hopkins University):
ASHRAE: American Society of Heating, Refrigerating and Air-Conditioning
Engineers:
AsMA: Aerospace Medical Association:
ATA: Air Transport Association:
ATR: Avions de Transport Regional:
BAe: British Aerospace:
BRE: Building Research Establishment:
CAA: Civil Aviation Authority (United Kingdom):
CDC: Centers for Disease Control and Prevention:
CO: carbon monoxide:
CO2: carbon dioxide:
DOT: Department of Transportation:
ECS: Environmental Control System:
EPA: Environmental Protection Agency:
FAA: Federal Aviation Administration:
FARS: Federal Aviation Regulations:
GAO: General Accounting Office:
HEPA: high-efficiency particulate air:
IAPA: International Airline Passengers Association:
IATA: International Air Transport Association:
JAA: European Joint Aviation Authorities:
NEJM: New England Journal of Medicine:
NIOSH: National Institute for Occupational Safety and Health:
NRC: National Research Council:
O3: ozone:
RPM: revenue passenger mile:
SARS: severe acute respiratory syndrome:
TB: tuberculosis:
URI: upper respiratory tract infection:
WHO: World Health Organization
Letter January 16, 2004:
The Honorable Peter DeFazio:
Ranking Democratic Member:
Subcommittee on Aviation:
Committee on Transportation and Infrastructure:
House of Representatives:
Dear Mr. DeFazio:
The quality of air in commercial airliner cabins has long been a
concern of the traveling public, the medical community, and
particularly flight attendants, who fly often. Air quality, in the
context of airliner cabins, refers to the extent to which airflow, low
humidity, and air pressure[Footnote 1] and contaminants such as
pollutants and infectious disease pathogens affect the healthfulness of
the air. Air travelers, flight attendants, and the medical community
have raised questions about the extent to which cabin air contributes
to discomfort, such as dry eyes and nose, and to more serious health
effects, such as upper respiratory infections. Interest in cabin air
quality heightened in 2003, with reports that a small number of severe
acute respiratory syndrome (SARS) infections may have occurred on board
aircraft serving areas with SARS outbreaks.[Footnote 2] In 2001, the
National Research Council[Footnote 3] issued a report that assessed
airborne contaminants in commercial aircraft, including an evaluation
of their toxicity and associated health effects; addressed cabin
pressure (oxygen supply) and ventilation; and recommended approaches to
improving data on cabin air quality.[Footnote 4]
Given this backdrop, you asked us to provide information on steps that
the aviation community is taking to address concerns about cabin air
quality. Specifically, you asked us to address the following questions:
(1) What is known about the major potential health effects of air
quality in commercial airliner cabins on passengers and flight
attendants? (2) What actions has the National Research Council
recommended to improve cabin air quality, and what is the status of
those actions? (3) What technologies are available today to improve the
air quality in commercial airliner cabins, and which, if any, should be
required?
To address these questions we reviewed the December 2001 National
Research Council report on airliner cabin air quality because it was
the most current and comprehensive work of its kind in this area. The
Council is the principal operating agency of the National Academy of
Sciences, which was chartered by Congress to advise the federal
government on scientific and technical matters. To produce the report,
the Council convened a committee of experts in the fields of industrial
hygiene, exposure assessment, toxicology, occupational and aerospace
medicine, epidemiology, microbiology, aerospace and environmental
engineering, air monitoring, ventilation and airflow modeling, and
environmental chemistry. (App. II lists the members of the committee.)
The committee examined the existing literature on this issue and made
recommendations for potential approaches for improving cabin air
quality. We also independently reviewed other studies on issues related
to cabin air quality, paying particular attention to those issued after
the publication of the National Research Council report.[Footnote 5] We
also gathered information from airlines and the governments of
Australia, Canada, and the United Kingdom because of the research these
countries have done on airliner cabin air quality. We also interviewed
officials representing the World Health Organization (WHO), the Centers
for Disease Control and Prevention (CDC), the Federal Aviation
Administration (FAA), the National Institute for Occupational Safety
and Health (NIOSH), the Aerospace Medical Association (AsMA), the Air
Transport Association (ATA), the Association of Flight Attendants
(AFA), the International Airline Passengers Association (IAPA), and
aircraft and air filter manufacturers. We also interviewed several
recognized experts on cabin air quality issues. In addition, we
interviewed 11 of the 13 members[Footnote 6]of the National Research
Council Committee on Air Quality in Passenger Cabins of Commercial
Aircraft that produced the 2001 report to obtain their views on the
status of the report's recommendations and other cabin air quality
issues, including leveraging expertise outside of FAA, such as the
Environmental Protection Agency for its large body of research on
indoor air quality and NIOSH for its role in conducting public health
and air quality research. Finally, we contacted the 14 largest U.S.
airlines that use Airbus, Boeing, or McDonnell Douglas aircraft to
determine the extent to which their aircraft fleets use high-efficiency
particulate air (HEPA) filters[Footnote 7] on recirculated cabin air.
Twelve of these 14 airlines responded, allowing us to determine HEPA
filter usage rates for approximately 90 percent of the aircraft in our
study population. We also obtained information from an aviation
publication and the manufacturers of regional jets (typically aircraft
that seat 100 or fewer passengers) on the extent of HEPA filter usage
in these aircraft. We conducted our work from April 2003 through
December 2003 in accordance with generally accepted government auditing
standards. See appendix I for additional information on our objectives,
scope, and methodology.
Results in Brief:
Despite a number of studies of the air contaminants that passengers and
flight attendants are potentially exposed to in airliner cabins and
complaints by cabin occupants about health effects from poor cabin air
quality, little is known about the extent of associated health effects.
Reports published by the National Research Council in 1986 and 2001 on
what was then known about airliner cabin air quality concluded that
more research was needed to determine the nature and extent of health
effects on passengers and cabin crew and that available air quality
data are not adequate to address critical questions on aircraft cabin
air quality and its possible effects on cabin occupant health. While
aircraft manufacturers have made significant improvements to aircraft
ventilation systems, passengers and cabin crews are still exposed to a
number of air contaminants, such as allergens and infectious agents.
Passengers and crew are also subjected to airflow rates that are lower
than those recommended for buildings and to air pressures and humidity
levels that are lower than those normally present at or near sea level.
This exposure can pose a health risk to passengers with certain medical
conditions, such as lung, heart, and circulatory disorders. In
addition, poor cabin air quality has been associated with such
discomforts as eye and nasal passage irritation.
The 2001 National Research Council report on airliner cabin air quality
made 10 recommendations directed largely to the Federal Aviation
Administration (FAA) to collect more information on the potential
health effects of cabin air quality and to review the adequacy of its
standards for air quality in commercial airliner cabins. To varying
degrees, the agency has addressed the recommendations for which it is
responsible. FAA is attempting to balance the need for additional
research on the potential health effects of cabin air quality with
other research priorities, such as improving passenger safety. However,
some in the aviation community, including members of the Council
committee who prepared the report, do not feel that FAA's planned
actions will adequately address all of its recommendations on cabin air
quality. For example, several of the Council committee members were
particularly concerned about FAA's approach to implementing the
committee's principal recommendations that more comprehensive research
on the health effects of cabin air quality is needed. In response to
the committee's recommendations in this area, FAA is leading the
development of a surveillance and research program intended to relate
perceptions of discomfort or health-related symptoms of flight
attendants and passengers to possible causal factors, such as air
contaminants, reduced air pressures and airflows, jet lag, low
humidity, or inactivity. However, FAA has not yet developed a detailed
plan with key milestones and funding estimates for conducting the
planned surveillance and research program. In addition, of the 8
committee members who discussed the recommendations with us,[Footnote
8] all said that FAA's program was much more limited than the Committee
had envisioned. For example, 2 of the 8 said that FAA's program does
not include an adequate number and cross-section of aircraft types and
flights for accomplishing its objective. One committee member was also
concerned that the program is too heavily tied to the aircraft industry
to ensure objectivity and independence. In addition, another committee
member believes that although FAA has a committee to oversee the
selection of the contractor for the program, it has not assembled an
advisory committee to review the research design and monitor the
implementation of the program. In addition, 3 committee members are
concerned that the research effort may not be adequately funded.
Furthermore, 6 of the committee members felt that FAA's approach for
addressing its recommendation that increased efforts be made to provide
cabin crew, passengers, and health professionals with information on
health issues related to flying by creating links on the FAA Web site
to relevant information from health organizations was inadequate
because the links are difficult to navigate and need to be supplemented
with other information dissemination methods, such as providing
physicians with brochures to share with patients who are planning air
travel.
Several technologies are available today that could improve cabin air
quality (e.g., by filtering or removing contaminants, increasing cabin
humidity and raising cabin pressure, or absorbing more cabin odors and
gasses), but opinions vary on whether FAA should require aircraft
manufacturers and airlines to use these technologies. Aircraft
manufacturers contend that unless future research proves otherwise, the
ventilation systems in the aircraft that they have produced provide
ample amounts of relatively clean air. Most aircraft currently in
production have ventilation systems that recirculate cabin air. In
addition, all of the new large commercial airliners in production that
carry more than 100 passengers and have ventilation systems that
recirculate cabin air come equipped with high-efficiency particulate
air (HEPA) filters, which are highly effective (99.97 percent) at
capturing airborne contaminants, such as viruses, when properly fitted
and maintained. According to our survey of major U.S. air carriers, 85
percent of commercial airliners in the current U.S. fleet that
recirculate cabin air and carry more than 100 passengers use HEPA
filters. However, we found that only a small portion of the smaller
regional jets that recirculate cabin air are using these filters.
According to the manufacturers, most of these aircraft have no
provision for installing any type of filter for their recycled air and
could not be retrofitted with HEPA filters without extensive
modifications. Nevertheless, given the proven effectiveness of HEPA
filters, some National Research Council committee members and health
officials believe that FAA should require them on all aircraft with
recirculation systems. GAO also found that HEPA filters are relatively
low cost when their use does not require modifying the existing
ventilation system. In addition, airflow rates could be increased in
some aircraft by adjusting settings on the ventilation system to reduce
the effects of some airborne contaminants by diluting their
concentration. However, this would be done at the expense of higher
fuel consumption, increased engine emissions, and lower cabin humidity.
Finally, both Boeing and Airbus--the world's two largest airframe
manufacturers--are considering using air quality improvement
technologies (e.g., increasing cabin humidity) to improve passenger
comfort on the long-range commercial aircraft that they are developing.
To help ensure that FAA's research and surveillance efforts on airliner
cabin air quality answer critical outstanding questions about the
nature and extent of potential health effects of cabin air quality on
passengers and flight attendants, GAO recommends that the FAA
Administrator (1) develop a detailed plan for the research and
surveillance efforts, including key milestones and funding estimates;
(2) appoint a committee of acknowledged experts in the fields of
aircraft ventilation and public health, including representatives of
EPA and NIOSH, to assist in planning and overseeing the research and
surveillance efforts; (3) leverage the findings of international
counterparts' research on airliner cabin air quality to inform FAA's
surveillance and research efforts; and (4) report to Congress annually
on the progress and findings of the research and surveillance efforts
and funding needs.
In addition, to help improve the healthfulness of cabin air for
passengers and cabin crews, GAO also recommends that the FAA
Administrator assess the costs and benefits of requiring the use of
HEPA filters on commercial aircraft with ventilation systems that
recirculate cabin air. GAO also recommends that FAA should go farther
in addressing the Council recommendation to increase efforts to provide
the public with information on the health risks of flying by taking
additional steps to improve its methods for disseminating this
information, such as improving the ease with which the public can
access this information on FAA's Web site and systematically
disseminating such information to physicians and their patients through
various medical associations.
Background:
Since people began traveling in pressurized, climate-controlled
aircraft more than 40 years ago, questions have arisen about the
quality of air inside aircraft cabins and its effect on the health of
passengers and cabin crews. In addition, the number of people traveling
by commercial aircraft has increased dramatically over the years, with
more than 600 million passengers flown by U.S. carriers in 2002 alone.
Despite a downturn in air travel following the events of September 11,
2001, FAA expects demand to recover and then continue a long-term trend
of 3.6 percent annual growth. As air travel has become more accessible,
the flying public mirrors the general population more closely than in
years past. Therefore, it includes more young and elderly passengers
who can be more susceptible to potential health risks associated with
air travel. This diverse group of passengers, as well as the cabin
crew, experiences an environment in the aircraft cabin that in some
ways is similar to that of homes and buildings but in other ways is
distinctly different. The National Research Council (the Council)--the
principal operating agency of the National Academy of Sciences--has
issued two reports at the request of Congress on the air quality in
aircraft cabins, one in 1986 and another in 2001.[Footnote 9] The 2001
Council report notes that the aircraft cabin is a unique environment in
which the occupants are densely confined in a pressurized space. The
report goes on to note that airline passengers encounter environmental
factors that include low humidity, reduced air pressure, and potential
exposure to air contaminants, including ozone, carbon monoxide,
pesticides, various organic chemicals, and biological agents that can
have serious health effects. The report concluded that there are still
many unanswered questions about how these factors affect cabin
occupants' health and comfort and about the frequency and severity of
incidents in which heated oils or hydraulic fluids release contaminants
into the cabin ventilation system. Figure 1 shows the passenger cabin
of a commercial aircraft.
Figure 1: Passenger Cabin of Commercial Airliner:
[See PDF for image]
[End of figure]
As depicted in figure 2, supplying air to modern jet airliner cabins is
a complex process that varies somewhat among airplane models but has
essential characteristics that are shared by most airliners. Basically,
some of the outside air that enters the aircraft engines is diverted
and processed for use in the cabin in order to achieve an air pressure
and temperature closer to that experienced on the earth's surface. FAA
requires that air supplied to aircraft be designed to maintain a cabin
pressure equivalent to that at an elevation of no more than 8,000 feet,
which is similar to the elevation of Mexico City (7,500 ft.).
Nevertheless, the air pressures inside aircraft cabins are much higher
than the extremely low outside air pressures at normal cruising
altitudes of 25,000 to 40,000 feet. After flowing through the engines,
the air enters an intricate system of cooling devices and ducts and is
distributed throughout the cabin and cockpit. Airlines that fly in
areas where ozone levels are high[Footnote 10] are required to take
steps to ensure that ozone levels do not exceed prescribed standards
(e.g., by having a device that converts the ozone pollutant into oxygen
before it enters the cabin and cockpit). The Council reported that
unacceptable high ozone levels can occur in passenger cabins of
commercial aircraft in the absence of effective controls. On most
modern aircraft, an average of about 56 percent of the outside air
supplied to the cabin is vented out of the aircraft through valves that
help regulate cabin pressure. The remaining air is then recirculated
through the cabin; this recirculation allows the engines to use less
fuel for air supply and pressurization. In addition to less fuel and
pressurization, recirculation also provides the benefit of higher
airplane cabin humidity, improved airflow patterns, and minimized
temperature gradients. On most large aircraft, the recirculated air
typically passes through filters that are designed to remove harmful
particulates, such as viruses and bacteria.[Footnote 11] FAA requires
that aircraft ventilation systems for aircraft designs certified after
June 1996 be designed to supply at least 10 cubic feet per minute of
outside air per person under standard operating conditions. This
compares with the standard minimum rate of 15 cubic feet per minute per
person for buildings recommended by the American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE).[Footnote 12]
However, according to FAA officials, there is currently no standard for
cabin ventilation rate, and it has yet to be determined if it is
appropriate to compare building and aircraft ventilation rates because
outside air at altitude is very clean, while air sources for buildings
are often contaminated by pollution. Furthermore, in rare instances,
oil leaks or other engine malfunctions can cause contaminants such as
carbon monoxide to be released into the cabin ventilation system. The
2001 Council report noted that questions about the frequency and
significance of such incidents remain unanswered. In February 2002, FAA
published a report that discussed many of the issues in the Council
report, including an estimate of 416 air contaminant events (or 2.2
events every 1,000,000 aircraft hours) that may have taken place in
commercial transports within the United States between January 1978 and
December 1999.
Figure 2: Overview of How Air Is Supplied on a Commercial Airliner:
[See PDF for image]
(1) Outside air continuously enters the engine, where it is compressed.
(2) It then passes through a catalytic ozone converter (in some
aircraft) to air-conditioning packs.
(3) The air passes through cooling packs to a mixing manifold.
(4) Outside air entering the mixing manifold is mixed with recirculated
air that has been cleaned with high-efficiency filters.
(5) The makeup of air in the mixing manifold is approximately 50
percent outside and 50 percent filtered, recirculated air.
(6) Air from the mixing manifold is then supplied to the cabin on a
continuous basis from overhead outlets.
(7) As outside air enters the airplane, air is continuously exhausted
from the airplane.
(8) Mixed outside and filtered recirculated air is provided to the
flight deck from the mixing manifold.
[End of figure]
FAA is responsible for setting design standards for aircraft
ventilation systems. To fulfill its responsibilities, FAA requires that
manufacturers design and build their large commercial airplanes to meet
specific engineering standards, which limit the amounts of certain air
quality contaminants (e.g., carbon monoxide, carbon dioxide, and ozone)
that can be present in an airliner cabin. Manufacturers comply with
these engineering standards in order to have FAA certify their
airplanes as airworthy.[Footnote 13] However, while FAA monitors
overall aircraft system operations, it does not require airlines to
monitor cabin air quality during their operations to determine if air
quality during routine flight operations is meeting the agency's
engineering standards. According to FAA, the certification requirements
combined with the monitoring of overall aircraft system operations are
sufficient. However, the 2001 Council report stated that because of a
lack of data it was not able to answer questions about the extent to
which aircraft ventilation systems are operated properly.
Despite a Number of Studies, Data Are Lacking About the Effects of Air
Quality On Cabin Occupants:
Passengers and flight attendants have had long-standing concerns about
negative health effects from the quality of air in airliner cabins;
however, research to date, including two reports by the Council, has
not been able to definitively link the broad, nonspecific health
complaints of passengers and flight attendants to possible causes,
including cabin air quality. In its most recent report, the Council
concluded that critical questions about the potential effect of cabin
air quality on the health of cabin occupants remain unanswered because
existing data are inadequate, and it recommended further research to
narrow this knowledge gap.
Passengers and flight attendants (cabin occupants) have long complained
of acute and chronic health effects during and after flying. Many
complaints made by cabin occupants are relatively minor, such as dry
eyes and nose, or the onset of colds soon after flying, but others are
much more serious. According to the Association of Flight Attendants,
its members have reported such health problems as respiratory diseases,
nausea, dizziness, muscle tremors, nervous system damage, and memory
loss.[Footnote 14] The association notes that these illnesses are
consistent with exposure to carbon monoxide, pesticides, reduced oxygen
levels, neurotoxins, and ozone gas, all of which can be present in the
cabin itself or in cabin air supplies, depending on the flight. In
addition, passengers with certain medical conditions can be at higher
risk from the quality of cabin air than the general population due to
air contaminants, lowered oxygen levels in the body (hypoxia), and
changes in cabin pressure. Such medical conditions include limited lung
capacity (e.g., asthma) and cardiovascular and circulatory disorders.
Those who fly soon after surgery are particularly vulnerable to changes
in cabin pressure. However, according to the Council report, many of
the complaints made by cabin occupants are so broad and nonspecific
that they could have many causes, and it is difficult to determine a
specific illness or syndrome.
Although numerous studies have been conducted on cabin air quality
issues, there are insufficient data to determine the nature and extent
of cabin air quality's effect on cabin occupants. Council reports
published in 1986 and 2001 reviewed the literature on cabin air quality
issues and concluded that the studies had not collected data in a
systematic manner that would conclusively address many of the questions
about potential exposures in aircraft cabins and their health effects.
Both reports recommended actions for improving what is known about
cabin air quality, including the need to collect better data on the
potential effect of cabin air quality on passenger and cabin crew
health. The 2001 report concluded that available data on air quality
and its possible negative effects on cabin occupant health have left
three critical outstanding questions unaddressed and that additional
research is needed:
* Do current aircraft as operated comply with FAA design and
operational limits for ventilation rate and for chemical contaminants,
including ozone, carbon monoxide, and carbon dioxide, and are the
existing air quality regulations adequate to protect health and ensure
the comfort of passengers and cabin crew?
* What is the association, if any, between exposure to cabin air
contaminants and reports or observations of adverse health effects in
cabin crew and passengers?
* What are the frequency and severity of incidents when air
contaminants enter the cabin due to nonroutine conditions such as oil
leaks or other engine malfunctions?
Following the 1986 report, the Department of Transportation sponsored a
study to evaluate the health risks posed by exposures to contaminants
on randomly selected flights. In addition, various researchers
conducted a number of studies of cabin air quality issues, including
eight investigations of biological agents, such as viruses and
bacteria, on commercial aircraft. However, these and other studies were
not able to link the broad, nonspecific health complaints that
passengers and cabin crew continued to make to possible causes,
including cabin air quality.
Recognizing the need for more data on the issue, Congress directed FAA,
in AIR-21,[Footnote 15] to request that the Council perform another
independent examination of cabin air quality. The Council's report,
issued in 2001, concluded that when operated properly, the
environmental control system[Footnote 16] should provide an ample
supply of air to pressurize the cabin, meet general comfort conditions,
and dilute or reduce normally occurring odors, heat, and contaminants.
However, the Council also found that the design standard for
ventilation rates[Footnote 17] in aircraft required by FAA was less
than one-half to two-thirds the rate recommended by ASHRAE for
buildings. The Council noted that whether the building ventilation
standard is appropriate for the aircraft cabin environment has not been
established.[Footnote 18] Studies have shown that low ventilation rates
in buildings have contributed to "sick building syndrome," which causes
fatigue, headache, and throat irritation. However, FAA officials told
us that a sick building syndrome comparison is not applicable, in part
because HEPA filtration results in much cleaner recirculated air than
in a building environment.
The 2001 Council report also found that although the environmental
control system in aircraft is designed to provide adequate air pressure
and minimize the concentration of contaminants in the cabin, passengers
and cabin crew are potentially exposed to air quality-related health
risks. The Council was particularly concerned about two cabin air
characteristics and suggested that they be given high priority for
further investigation. The first is reduced oxygen partial pressure,
which results from the lower air pressures present in aircraft cabins
at cruise altitudes. Most healthy individuals are unaffected by reduced
oxygen partial pressure, but those with health problems such as
cardiopulmonary disease and infants can experience serious health
effects from a lack of oxygen (e.g., respiratory stress). The other
concern of the Council was elevated concentrations of ozone, which can
occur at high cruise altitudes over certain areas of earth, such as the
Arctic. The Council reported that unacceptably high ozone levels could
occur in passenger cabins of commercial aircraft in the absence of
effective controls. FAA allows aircraft operators to maintain cabin
ozone concentrations at or below prescribed limits through flight
planning that avoids areas with ozone concentrations exceeding those
limits or the installation of devices that convert ozone to oxygen.
However, FAA does not have a process in place to ensure that ozone
converters are installed in all aircraft that fly routes where ozone
may pose a risk or that converters in service are operating properly.
The Council also had what it termed moderate concern about several
other potential air quality-related exposures on aircraft, but it noted
that there were little data available on the frequency at which they
occur. For example, according to the Council, infectious agents, such
as viruses and bacteria, were likely present on aircraft, and high
occupant densities could increase the risk of transmittal. The Council
observed, however, that air recirculation did not increase the risk of
transmittal, especially in systems using HEPA filters. Likewise, the
Council noted that airborne allergens, such as cat dander, could pose
problems for passengers with sensitivities. In addition, when aircraft
are on the ground, according to the Council, passengers can be exposed
to contaminants from engine exhaust, such as carbon monoxide and other
outdoor air pollutants, including ozone and particulate matter, when
they are pulled into the aircraft through the ventilation system. Also
of some concern to the Council were incidents when lubricating and
hydraulic fluids seep into the aircraft ventilation system during
engine and other system malfunctions. Although such occurrences are
rare, and the actual exposure to contaminants resulting from them is
unknown, lubricating and hydraulic fluids contain substances that can
pose neurological health risks to passengers and cabin crew if they are
present in sufficient concentrations and for a sufficient length of
time. Finally, the Council was somewhat concerned about exposures to
the pesticide spraying that takes place on some international
flights,[Footnote 19] which can cause skin rashes and other health
effects. Table 1 summarizes information presented by the Council on the
potential air quality-related exposures on aircraft.
Table 1: Potential Air Quality Related Concerns on Aircraft Cited by
the National Research Council in 2001:
High concern:
Characteristic: Cabin pressure:
Potential health impacts: Serious health effects may occur in infants
and those with cardio-respiratory diseases from lack of oxygen.
Temporary discomfort or pain from gas expansion in middle ears or
sinuses;
Exposure frequency: Reduced cabin pressure occurs on nearly all
flights;
Availability of information: Reliable measurements are available;
health effects in some sensitive groups are uncertain.
Characteristic: Ozone:
Potential health impacts: Airway irritation and reduced lung function;
Exposure frequency: Elevated concentrations are expected primarily on
aircraft without ozone converters;
Availability of information: Few systematic measurements made since
1986 Council report.
Moderate concern:
Characteristic: Airborne allergens:
Potential health impacts: Irritated eyes and nose, sinusitis, acute
increases of asthma, or anaphylaxis;
Exposure frequency: Not known;
Availability of information: Only self- reported data are available.
Characteristic: Carbon monoxide:
Potential health impacts: Headaches and lightheadedness occur at low
concentrations, more serious health effects result from higher
concentrations;
Exposure frequency: High concentrations could occur during air-quality
incidents. Frequency of incidents is highly uncertain but is believed
to be low;
Availability of information: Reliable measurements are available for
normal operating conditions, but no data are available for incidents.
Characteristic: Hydraulic fluids:
Potential health impacts: Mild to severe health effects can result
from exposure to these fluids;
Exposure frequency: Frequency of incidents in which these fluids enter
the cabin is uncertain but is expected to be relatively low;
Availability of information: No quantitative data are available.
Little information is available on health effects related to smoke,
mists, or odors in aircraft cabins.
Characteristic: Pesticides:
Potential health impacts: Skin rashes can result from skin or
inhalation exposure;
Exposure frequency: Exposure likely on some international flights;
Availability of information: Only self-reported data are available.
Low Concern:
Characteristic: Carbon dioxide:
Potential health impacts: Indicator of ventilation adequacy. Elevated
concentrations associated with increased perceptions of poor air
quality;
Exposure frequency: Concentrations are generally below FAA regulatory
limits;
Availability of information: Reliable measurements are available only
for normal operating conditions.
Characteristic: Nuisance odors:
Potential health impacts: Annoyance and mucous membrane irritation can
occur;
Exposure frequency: Can be present on any flight;
Availability of information: Reliable information is available from
surveys of cabin occupants.
Characteristic: Relative humidity:
Potential health impacts: Temporary drying of skin, eyes, and mucous
membranes can occur at relative low humidity (10 to 20%);
Exposure frequency: Relative low humidity occurs on most flights;
Availability of information: Reliable and accurate measurements in
aircraft are available.
Source: National Research Council.
[End of table]
Since the issuance of the 2001 Council report, some limited studies
have examined specific air quality issues, such as infectious disease
transmission, but they have raised as many questions as they have
answered. For example, according to a revised 2003 WHO report on
tuberculosis (TB) and air travel, as of August 2003, no case of active
TB has been identified as resulting from exposure while on a commercial
aircraft.[Footnote 20] The report did note, however, that there is some
evidence that transmission of TB may occur during long flights (i.e.,
more than 8 hours) from an infectious source (passenger or crew) to
other passengers or crewmembers. In 2002, the American Medical
Association[Footnote 21] did not find any evidence that aircraft cabin
air recirculation increases the risk for upper respiratory tract
infection (URI) symptoms in passengers traveling aboard commercial
jets. However, passengers had higher incidents of URI infections than
the general public within a week after completing their trips. One of
the study's authors noted that the research indicated that while flying
increases the risk of getting colds or other infections, an aircraft's
ventilation system may not be a key factor. A 2003 study appearing in
the New England Journal of Medicine found that SARS transmissions may
occur on flights carrying people in the symptomatic stages of the
disease. (See app. II for more details on this study.[Footnote 22]):
FAA has Taken Action to Address Council Recommendations On Cabin Air
Quality, but These Efforts Could Be Improved:
The December 2001 Council report on airliner cabin air quality made 10
recommendations about air quality standards for the cabins of
commercial airliners and the need for more information concerning the
health effects of cabin air. Nine of these recommendations were
directed to FAA, and it has implemented them to varying degrees. The
Council report's 10 recommendations focused on five aspects of cabin
air quality and its environment: (1) the establishment of cabin air
quality surveillance and research programs, (2) FAA's oversight of the
operation of aircraft ventilation systems, (3) exposures on aircraft
due to the transport of small animals in aircraft cabins, (4)
distribution of health related information, and (5) recommended
procedures as a result of a ventilation system shutdown. Although one
recommendation asked Congress to designate a lead federal agency for
conducting airliner cabin air quality research, most of the
recommendations were directed at or involved FAA. Table 2 describes
each of the Council report recommendations and FAA's response.
Table 2: Status of the National Research Council's 2001 Report
Recommendations on Airliner Cabin Air Quality:
Cabin Air Quality Surveillance and Research Request:
Council Report Recommendations: Surveillance program; To be consistent
with FAA's mission to promote aviation safety, an air quality and
health- surveillance program should be established. The objectives and
approaches of this program are summarized in appendix V of this
report. The health and air quality components should be coordinated so
that the data are collected in a manner that allows analysis of the
suggested relationship between health effects or complaints and cabin
air quality; FAA's Response: FAA is addressing this recommendation
through a joint research effort combining the resources of FAA and the
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE).
Council Report Recommendations: Research program; To answer specific
questions about cabin air quality, a research program should be
established. See appendix V of this report for a summary of research
questions, objectives, and research program approach; FAA's Response:
FAA is addressing this recommendation through a joint research effort
combining the resources of FAA and ASHRAE.
Council Report Recommendations: Research program lead agency; The
Council committee recommends that Congress designate a lead federal
agency and provide sufficient funds to conduct or direct the research
program recommendation (see above), which is aimed at filling major
knowledge gaps identified in this report. An independent advisory
committee with appropriate scientific, medical, and engineering
expertise should be formed to oversee the research program to ensure
that its objectives are met and the results publicly disseminated;
FAA's Response: Congress has designated FAA as the lead agency to
direct the cabin air quality research program, but, according to FAA
officials, has not appropriated sufficient funds to support it.
FAA Oversight of Aircraft Ventilation Systems:
Council Report Recommendations: Air quality regulations; FAA should
rigorously demonstrate in public reports the adequacy of current and
proposed Federal Aviation Regulations (FARs) related to cabin air
quality and should provide quantitative evidence and rationales to
support sections of the regulations that establish air quality-related
design and operational standards for aircraft (standards for carbon
monoxide, carbon dioxide, ozone, ventilation, and cabin pressure). If
a specific standard is found to be inadequate to protect the health
and ensure the comfort of passengers and crew, FAA should revise it.
For ventilation, the committee recommends that an operational standard
consistent with the design standard be established; FAA's Response:
Necessary data to implement this recommendation will be available upon
completion of the ASHRAE study in late 2006 or early 2007.
Council Report Recommendations: Regulations for ozone; FAA should take
effective measures to ensure that the current FAR for ozone (average
concentrations not to exceed 0.1 ppm above 27,000 ft; and peak
concentrations not to exceed 0.25 ppm above 32,000 ft.) is met on all
flights, regardless of altitude. These measures should include a
requirement that either ozone converters be installed, used, and
maintained on all aircraft capable of flying at or above those
altitudes, or strict operating limits be set with regard to altitudes
and routes for aircraft without converters to ensure that the ozone
concentrations are not exceeded in reasonable worst-case scenarios. To
ensure compliance with the ozone requirements, FAA should conduct
monitoring to verify that the ozone controls are operating properly
(see also surveillance program recommendation); FAA's Response:
Necessary data to implement this recommendation will be available upon
completion of the ASHRAE study.
Council Report Recommendations: Air cleaning equipment; FAA should
investigate and publicly report on the need for and feasibility of
installing air cleaning equipment for removing particles and vapors
from the air supplied by the environmental control system (ECS) on all
aircraft to prevent or minimize the introduction of contaminants into
the passenger cabin during ground operation, normal flight, and air
quality incidents; FAA's Response: Necessary data to implement this
recommendation will be available upon completion of the ASHRAE study.
Council Report Recommendations: Carbon monoxide monitoring; FAA should
require a carbon monoxide monitor in the air supply ducts to passenger
cabins and establish standard operating procedures for responding to
elevated carbon monoxide concentrations; FAA's Response: Necessary
data to implement this recommendation will be available upon
completion of the ASHRAE study.
Exposures on Aircraft, Health Information, and Ventilation Shutdown
Procedures:
Council Report Recommendations: Allergens; Because of the potential
for serious health effects related to exposures of sensitive people to
allergens, the need to prohibit transport of small animals in aircraft
cabins should be investigated, and cabin crews should be trained to
recognize and respond to severe, potentially life-threatening
responses (e.g., anaphylaxis, severe asthma attacks) that
hypersensitive people might experience because of exposure to airborne
allergens; FAA's Response: FAA issued an advisory circular providing
guidance regarding air carrier passenger handling procedures for
allergen-sensitive people, but did not prohibit the transport of
animals on aircraft, particularly service animals. Agency officials do
not think that a prohibition on animals in the cabin would be
effective in minimizing animal allergens because they believe that
these allergens are brought on board aircraft primarily on the clothes
of passengers.
Council Report Recommendations: Health information; Increased efforts
should be made to provide cabin crew, passengers, and health
professionals with information on health issues related to air travel.
To that end, FAA and the airlines should work with such organizations
as the American Medical Association and the Aerospace Medical
Association to improve health professionals' awareness of the need to
advise patients on the potential risks of flying, including risks
associated with decreased cabin pressure, flying with active
infections, increased susceptibility to infection, or hypersensitivity; FAA's Response: The FAA's Office of Aerospace Medicine made health information and recommendations available to passengers and crews through its Web site and linked the site to other health-related organizations. The agency also developed a brochure on the potential risk of developing a condition known as deep vein thrombosis (DVT), in which blood clots can develop deep in the veins of the legs after extended periods of inactivity. This brochure has been distributed to aviation medical examiners and cited in the Federal Air Surgeon's Bulletin.
Council Report Recommendations: Ventilation shutdown; The committee
reiterates the recommendation of the 1986 Council report that a
regulation be established to require removal of passengers from an
aircraft within 30 minutes after a ventilation failure or shutdown on
the ground and ensure the maintenance of full ventilation whenever on-
board or ground- based air conditioning is available; FAA's Response:
FAA concurred with the objective of the recommendation and advised air
carriers, through advisory circulars, to deplane passengers as long as
operational safety is not compromised.
Sources: National Research Council and GAO analysis of FAA documents.
Note: Federal Aviation Regulations are legal requirements and rules for
the aviation industry set by the Federal Aviation Administration.
[End of table]
FAA formed the Airliner Cabin Environment Report Response Team to
review the findings of the NRC report on airliner cabin air quality and
published a planned response in February 2002. However, many of the
actions included in this plan were contingent on the formation of an
aviation rulemaking advisory committee, on which the agency has
deferred action. FAA subsequently updated its plans, as reflected
above.
We reviewed FAA's approach for addressing the recommendations and found
that the agency has made progress on implementing some of them,
including those relating to making information available on potential
health issues related to cabin air quality and the risks posed to
sensitive people by allergens from small animals transported in
aircraft cabins; however action on others is pending. For example,
recommendations to improve FAA oversight of aircraft ventilation
systems are pending until completion of the ASHRAE study in late 2006
or early 2007. In implementing the Council report recommendations, FAA
is attempting to balance the need to conduct additional research on the
healthfulness of cabin air quality with other research priorities, such
as improving passenger safety. Our prior work on airliner cabin safety
and health has underscored the importance of setting risk-based
research priorities, in part by establishing cost and effectiveness
estimates to allow direct comparisons among competing research
priorities. In commenting on this prior work, FAA cautioned that if too
much emphasis is placed on cost/benefit analyses, potentially valuable
research may not be undertaken.[Footnote 23] We concur in that caution.
Similarly, we found that many members of the Council committee on
airliner cabin air quality question FAA's approach to implementing some
of the recommendations it made, particularly those related to the
committee's principal finding that more comprehensive research on the
health effects of cabin air quality is needed. Specifically, some in
the aviation community have raised concerns that FAA's planned actions
for implementing the Council recommendations on cabin air quality,
including its research and surveillance efforts, will not be adequate
to answer long-standing questions about the nature and extent of
potential health effects posed by cabin air.
Council Recommendations Calling for Cabin Air Quality Surveillance and
Research Programs:
To address the need for more information on the health effects of cabin
air quality, the 2001 Council report made three recommendations
regarding the establishment of cabin air quality surveillance and
research programs. FAA, in coordination with ASHRAE, has begun to
develop a program to monitor air quality on some flights and correlate
this information with health data collected from passengers and cabin
crews. Although this effort can provide a foundation for future
research, members of the committee that produced the report are
concerned that its scope is too limited to adequately answer long-
standing questions concerning the association between cabin air quality
and health effects.
Council Concluded That Surveillance and Research Programs Needed to
Answer Outstanding Questions Concerning Cabin Air Quality:
According to a committee member, the Council report's most important
recommendations are those pertaining to the establishment of cabin air
quality surveillance and research programs. The report concluded that
available air quality data are not adequate to address three critical
questions on aircraft cabin air quality and its possible effects on
cabin occupant health:
* Do current aircraft, as operated, comply with FAA design and
operational limits for ventilation rate and for chemical contaminants,
including ozone, carbon monoxide, and carbon dioxide, and are the
existing air quality regulations adequate to protect the health and
ensure the comfort of passengers and the cabin crew?
* What is the association, if any, between exposure to cabin air
contaminants and reports or observations of adverse health effects in
cabin crew and passengers?
* What are the frequency and severity of incidents when air
contaminants enter the cabin due to nonroutine conditions such as oil
leaks or other engine malfunctions?
To answer these questions, the Council report recommended a dual
approach that includes a routine surveillance program and a more
focused research program. The report said that the surveillance program
should continuously monitor and record chemical contaminants, cabin
pressure, temperature, and relative humidity in a representative number
of flights over a period of 1 to 2 years. Thereafter, the program
should continue to monitor flights to ensure accurate characterization
of air quality as existing aircraft equipment ages or is upgraded. In
addition to air quality monitoring, the report said the surveillance
program should also include the systematic collection, analysis, and
reporting of health data, with the cabin crew as the primary study
group. The report said a detailed research program to investigate
specific questions about the possible association between air
contaminants and reported health effects should supplement the
surveillance program. Among the subjects suggested for research are the
factors that affect ozone concentration in cabin air and the adequacy
of outside air ventilation flow rates.
FAA Has Taken the Lead in Developing Surveillance and Research
Programs:
In order to implement the surveillance and research programs, the
report recommended that Congress designate a lead federal agency and
provide sufficient funding to conduct or direct the research program to
fill the major knowledge gaps. It also called for an independent
advisory committee with appropriate scientific, medical, and
engineering expertise to oversee the programs to ensure that the
research program's objectives are met. In response, as a part of FAA's
reauthorization, Congress designated FAA as the lead federal
agency.[Footnote 24] Prior to this, FAA acted in this capacity and
allocated limited funding for this effort, although, according to FAA
officials, Congress provided no additional funding through fiscal year
2003 for air quality surveillance and research; however, pending
legislation for fiscal year 2004 would provide $2.5 million for this
effort. In addition, on March 4, 2003, FAA announced the creation of a
voluntary program for air carriers, called the Aviation Safety and
Health Partnership Program. Through this program, the agency intends to
enter into partnership agreements with participating air carriers,
which will, at a minimum, make data on their employees' injuries and
illnesses available to FAA for collection and analysis. According to
FAA officials, this program has a reporting system and database
available to capture air quality incidents.
In taking the lead for implementing the recommendations for
surveillance and research programs, FAA has undertaken a joint effort
with ASHRAE. According to FAA, this joint effort will build on a
previous study conducted for FAA by NIOSH, which identified and
characterized potential health issues, including respiratory effects,
related to the aircraft cabin environment, but did not link the health
issues to cabin conditions.[Footnote 25] The joint effort includes a
surveillance and research initiative whose principal aim is to relate
perceptions of discomfort or health-related symptoms that flight
attendants and passengers have had to possible causal factors,
including cabin and outside air quality and other factors, such as
reduced air pressure, jet lag, inactivity, humidity, flight attendant
duty schedule and fatigue, disruptions to circadian rhythm,[Footnote
26] stress, and noise. While FAA's fiscal year 2004 appropriation in
the research and development budget includes $2.5 million for cabin air
research--including identifying bacterial and pesticide contamination
and monitoring air quality incidents--it is unclear which of the cabin
air quality projects outlined in the FAA reauthorization bill will be
funded.[Footnote 27] Additionally, ASHRAE officials stated that the
surveillance and research initiative would support ASHRAE's ongoing
efforts to develop air quality standards for commercial aircraft.
According to FAA, the surveillance and research program is to be
carried out in two parts; the first started in December 2003 and the
second will start in December 2004 and end in late 2006 or early 2007.
In part I, air quality data will be collected on four to six flights on
a minimum of two different types of aircraft, and the data will then be
compared with health information gathered from surveys of passengers
and crew on the flights. According to FAA and ASHRAE, the protocol and
procedures developed in part I of the study will be the basis for
conducting on-ground and in-flight monitoring in part II of the
initiative. In part II, air quality monitoring will be conducted on
different models of commercial jet airplanes representing a large
section of the world fleet and will include a minimum number of flights
that has not yet been determined.[Footnote 28] However, according to
FAA officials, the level of funding that will be available for part II
is uncertain. FAA and ASHRAE have assembled a committee which is
responsible for selecting a contractor to conduct the monitoring and
health surveillance in part I and overseeing the contractor's
performance. The committee consists of aircraft, health, and air
quality experts, including five members of the Council committee, as
well as representatives from FAA, the Association of Professional
Flight Attendants, and the Boeing Commercial Airplane Group. In
September 2003, the committee chose a contractor for part I, and work
began in December 2003. FAA and ASHRAE have not yet selected a
contractor for part II, although the estimated completion date for the
entire program is late 2006 or early 2007.
ASHRAE officials stated that to date FAA, Boeing, and two major U.S.
airlines are supporting this effort. FAA has provided $50,000 of the
estimated $250,000 it will cost to conduct air quality surveillance on
two aircraft. Boeing is the major source for the balance of the funding
for the surveillance program. FAA had previously reported that it was
seeking a $500,000 contract with the Johns Hopkins University Applied
Physics Laboratory (APL) to develop devices to monitor the aircraft
cabin environment as part of the research and surveillance program.
However, the contract was not finalized because APL determined that the
project would cost significantly more than $500,000 and FAA
reprogrammed the funds. FAA said that it has not yet funded part II,
while ASHRAE officials noted that they are planning to solicit the part
I contributors again for part II once part I is under way.
Despite FAA's efforts to date, we found that the agency has not
developed a detailed plan for the research and surveillance program,
including key milestones and funding estimates, in keeping with
generally accepted practices for oversight and independence. In
addition, the agency has not created an independent panel of experts in
the areas of aircraft ventilation, air quality, and public health to
help plan and oversee this effort. Furthermore, FAA's plans do not
explicitly include leveraging the findings of international research on
cabin air quality.
Committee Members Concerned about Scope, Independence, and Funding of
FAA Surveillance and Research Program:
Members of the committee that produced the 2001 Council report are
concerned that the FAA/ASHRAE surveillance and research program, as
designed, will fall short of answering the long-standing questions
about the effect of cabin air quality on passenger and cabin crew
health and comfort. We contacted the 13 members of the committee, and 8
agreed to comment on FAA's response to their recommendations on cabin
air quality surveillance and research. We refer to these 8 individuals
from here forward as commenting committee members. Although 5 of 8
commenting committee members said that the initiative should shed some
light on cabin air quality's effects on health, all said that it was
much more limited than the committee had envisioned. Two of the 8
commenting committee members thought that the air quality and health
surveillance initiative should be a continuous undertaking in which air
quality and health information is taken from a representative sample of
commercial aircraft and flight routes. They also said that it appears
the FAA and ASHRAE program will not include a broad enough cross-
section of aircraft and flights to determine the full range of air
quality problems and relate them to health effects. Two commenting
committee members said that part I of the FAA and ASHRAE program will
extensively monitor cabin air quality on two aircraft types; however,
part I will not provide information that is generalizable to the U.S.
commercial airliner fleet. According to Boeing officials involved in
this study, part I research is designed to validate test equipment and
study protocols and is not designed to be generalized to the airliner
fleet. One committee member said that although more aircraft are to be
included in part II, it is doubtful that enough information will be
collected to adequately answer the key questions the agency's research
and surveillance program was designed to address. According to Boeing
officials, part II includes plans for information collection to address
the key question of the agency surveillance and research program,
provided sufficient funds are available. Another commenting committee
member said that the FAA and ASHRAE program would also yield little or
no information on air quality incidents that occur when cabin air is
contaminated by oil or hydraulic fuel leaks. According to the member,
these incidents are rare and can be monitored only if simple,
inexpensive equipment (e.g., devices that can "grab" samples) is
available to cabin crew on a large number of flights to use in the
event that an incident occurs. FAA officials said that issues of
sampling adequacy and specimen handling could complicate the grab
sample approach. These officials also noted that a voluntary injury and
illness reporting system that it has in place could capture air quality
incidents if it were made mandatory.
Seven of the eight commenting committee members also noted that FAA has
not adequately addressed the Council report's recommendations regarding
cabin air surveillance and research programs. FAA has indicated that
its program responds to the report's recommendations calling for
surveillance and research efforts. However, these committee members
believe that the program focuses only on surveillance and does not
include in-depth research of air quality issues as outlined in the
committee's recommendation calling for a separate comprehensive
research program.
One of the commenting committee members said that a cabin air quality
study currently under way in Europe contains many of the elements that
the committee had hoped to see in the U.S. surveillance and research
efforts. As part of the ongoing surveillance and research study, the
European cabin air study[Footnote 29] is currently coordinated by
Building Research Establishment, Ltd. (BRE).[Footnote 30] The study
focuses on three major goals: (1) advancing the industry's
understanding of what is known about air quality issues by assessing
the current level of air quality found in aircraft cabins; (2)
identifying the technology (i.e., environmental control systems
including filtration and air distribution) that is available to improve
cabin air quality; and (3) assessing and determining potential
improvements to existing standards and performance specifications for
the cabin environment. (The scope and methodology for Europe's cabin
air study is found in appendix IV). The cabin air study partnered (to
various degrees) with 16 organizations, including Boeing, Airbus
Deutschland, Honeywell (manufacturer of environmental control
systems), Pall Aerospace (filter manufacturer), British Airways, United
Kingdom's Civil Aviation Authority (CAA), European Joint Aviation
Authorities (JAA), and other organizations representing Austria,
France, Germany, Greece, Norway, Poland, and Sweden. The European cabin
air study began on January 2001 with an estimated cost of $8 million
and is expected to disclose its findings in 2004.[Footnote 31]
Of the eight commenting committee members, three addressed the funding
of the FAA and ASHRAE surveillance and research programs. These members
said that the amount of funding available for U.S. efforts might be
insufficient to conduct surveillance and research programs of the scope
they envisioned in their recommendations. For example, one of the
committee members stated that to conduct a surveillance and research
program of the scope the Council had in mind, Congress would have to
provide funding levels comparable to that of the European cabin air
study.
One commenting committee member, National Institute for Occupational
Safety and Health (NIOSH) officials, and airline flight attendant
representatives we interviewed expressed concern that the extensive
involvement of aircraft manufacturers and airlines in the design and
implementation of the FAA and ASHRAE program could threaten the
independence of the effort. However, with the exception of the flight
attendant representatives,[Footnote 32] they agreed that any
surveillance and research programs require participation by these
groups. Nonetheless, they point to the fact that much of the available
funding for the initiative ($200,000 of the $250,000) is coming from
the aviation industry, which has a stake in the outcome, and that this
might give the impression that the study lacks the necessary
objectivity. The commenting committee member suggested that the
research money provided by the aviation industry be placed in a special
fund that would be managed by FAA or an independent research group.
According to ATA officials, due to a lack of public funding on a scale
comparable to what has been provided for Europe's cabin air study, the
financial support and cooperation of aircraft manufacturers and
airlines is essential if FAA is to conduct this research. In addition,
Boeing officials stressed that the project funding is currently
controlled by ASHRAE and the project oversight committee is led by the
chairman of the Council study.
Five of the commenting committee members also discussed the status of
their recommendation concerning the need for Congress to designate a
lead federal agency and advisory committee for the air quality research
effort. Although Congress designated FAA as the lead agency in November
2003, FAA had already assumed responsibility for implementing the
research and surveillance-related recommendations. In commenting on the
Council recommendation to designate a lead federal agency, several
members said they thought that the lead agency should be one that is
experienced in conducting scientific research on air quality and
environmental health issues. Some noted that the Environmental
Protection Agency (EPA) has supported a large body of research into air
quality issues, and another pointed out that NIOSH has performed
studies of air quality in buildings and the workplace. Several
commenting members indicated that although it is FAA's mission to
promote aviation safety, they had reservations about whether the agency
was well suited to oversee a large air quality research program on its
own. Several members thought that, as an alternative, FAA might be part
of a cooperative federal effort to perform airliner cabin air quality
research. In addition, another committee member believes that although
FAA has a committee to oversee the selection of the contractor for the
program, it has not assembled an advisory committee to review the
research design and monitor the implementation of the program.
Council's Recommendations Concerning FAA Oversight of Aircraft
Ventilation Systems:
Four of the Council recommendations pertain to FAA's oversight of the
operation of aircraft ventilation systems. These recommendations call
for FAA to (1) demonstrate in public reports the adequacy of its
regulations related to cabin air quality and establish operational
standards for ventilation systems, (2) ensure that standards for ozone
levels are met on all flights, (3) investigate the need for and
feasibility of installing equipment to clean the air supplied to
aircraft ventilation systems, and 4) require carbon monoxide monitors
in air supply ducts to passenger cabins and establish procedures for
dealing with elevated carbon monoxide concentrations. According to FAA
officials, the agency originally planned to have an aviation rulemaking
advisory committee assess whether current standards were appropriate
for ensuring that aircraft ventilation systems adequately prevent
contamination of cabin air. However, FAA decided to defer this action
until data is available from the surveillance and research study, as
well as the European cabin air study. Additionally, FAA believes that
data from this study will aid in the reconsideration of air quality
standards for commercial aircraft. However, most of the commenting
committee members questioned the need for delay in addressing some of
the recommendations.
Four of the eight commenting committee members said that they
recommended that FAA demonstrate, in public records, the rationale for
the established design standards for carbon monoxide (CO), carbon
dioxide (CO2), ozone (O3), ventilation, and cabin pressure because FAA
was unable to explain the reasoning for these standards. For example,
FAA has not documented the reasons for setting the ventilation rate
standard for aircraft cabins of new aircraft types at .55 pounds of
outside air per minute per occupant. The American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE)[Footnote 33]
recommends that ventilation rates inside a building environment be at
least 1.1 pounds of outside air per minute per occupant, which is about
50 percent more than the current FAA requirement for aircraft. In
addition, FAA has not documented the reasons for requiring a design for
cabin air pressure altitude of not more than 8,000 feet air pressure,
which is about three-fourths of the air pressure found at sea level.
Members of the research community, including the Aerospace Medical
Association (AsMA) and CAA, state that the loss of air pressure and
oxygen may pose serious health risks for infants whose lungs have not
fully developed and for older adults who may have upper respiratory
problems.
In response to the committee members' comments, FAA provided us the
following explanations for the design standards in question. The
ventilation rate standard was based on a regulatory value established
decades ago, which has been shown to be acceptable, and ASHRAE has
formed a subcommittee to develop a standard specifically for airplanes.
The limit for carbon monoxide concentration of 1 part in 20,000 parts
air (0.005 percent) was adopted from the Occupational Safety and Health
Administration (OSHA) and ASHRAE standards. The limit of maximum
allowable carbon dioxide concentration in occupied areas of transport
category airplanes was reduced to 0.5 percent in part due to a
recommendation from the National Academy of Sciences to review the
carbon dioxide limit in airplane cabins; it provides a cabin carbon
dioxide concentration level representative of that recommended by some
authorities for buildings. The ozone limits were based on studies
conducted by the FAA Civil Aerospace Medical Institute and are
comparable to standards adopted by the Environmental Protection Agency
and the Occupational Safety and Health Administration. The cabin
pressure altitude standard was based on the accepted industry practice
of maintaining the health and safety of occupants while considering the
structural limitations of the aircraft.
A commenting committee member also expressed concern that FAA certifies
aircraft ventilation systems that are designed to meet certain
standards, such as those for ventilation rates, but it does not require
that systems operate in accordance with these standards. The practical
effect is that aircraft are not monitored to determine if they meet the
design standards. According to another commenting committee member, FAA
did not need data from the planned research project to provide a
rationale for ventilation system standards, or to require that
ventilation systems operate according to standards. Some committee
members also said that FAA could begin to take steps to ensure that
ozone standards are met on all flights regardless of altitude and
require monitors for dangerous carbon monoxide vapors in air supply
ducts to passenger cabins before the completion of the planned research
study. FAA officials said that although it does not conduct recurrent
system design compliance checks, the agency uses various reporting
systems to monitor aircraft system performance and takes appropriate
mandatory action when an unsafe condition is found.
Council Recommendation Concerning Airborne Allergens:
Because of the potential for serious health effects for people
sensitive to allergens, the 2001 Council report also recommended that
FAA investigate the need to prohibit the transport of small animals in
aircraft cabins and provide training to cabin crews to deal with
allergic reactions. However, FAA does not think that prohibiting
animals in the cabin would be effective because it believes that most
animal allergens are brought onboard aircraft on the clothes of
passengers rather than by the animals themselves. Instead, the agency
issued an advisory circular highlighting the effective procedures that
passengers can use when carrying animals and guidance on how to train
crewmembers to recognize and respond to in-flight medical events that
result from exposure to allergens. Additionally, FAA will enhance its
Internet site to provide general information related to FAA and air
carrier policy concerning the transport of animals in aircraft cabins.
Commenting committee members generally supported FAA's approach to this
recommendation.
Council Recommendation Concerning Health Information:
In response to the Council report recommendation calling for FAA to
increase efforts to provide cabin crew, passengers, and health
professionals with information on health issues related to air travel,
FAA modified the general information section of its Web site; however,
we found that the traveler health information is not easy to access.
FAA created hyperlinks to other Web sites, such as those of the
Aerospace Medical Association and Centers for Disease Control and
Prevention, which include information on potential health risks of
flying, particularly for health-challenged individuals. However, we
found it difficult to locate the section of the FAA Web site that deals
with traveler health information and when we did, it required several
steps to reach the hyperlinks. Some commenting committee members also
noted how difficult it is to access health-related information on the
FAA Web site. In addition to citing the need for FAA to increase the
accessibility of health-related information on its Web site, six of the
eight committee members also mentioned that FAA should take further
steps to make health information available to the flying public.
Suggestions included having airlines include health related information
on their Web sites and establishing a program to provide flying-related
heath risk information to physicians that they could then share with
their patients (e.g., through brochures).
Council Recommendation Concerning Aircraft Ventilation System
Shutdown:
FAA responded to the 2001 Council report recommendation that it
establish a regulation to require removal of passengers from an
aircraft within 30 minutes after a ventilation failure or shutdown on
the ground by issuing an advisory circular to airlines. Some commenting
committee members viewed this action as insufficient. This
recommendation reiterated one made in the 1986 Council report, which
FAA did not act on. The committees that produced both the 1986 and 2001
reports noted that environmental conditions in an aircraft cabin
respond quickly to changes in ventilation system operation. The
committees felt that the ventilation system should not be shut down for
a long period when the aircraft is occupied, except in the case of an
emergency, because excessive contaminant concentrations and
uncomfortably high temperatures can occur quickly. Several commenting
committee members told us that they felt strongly that FAA should
require passenger removal in the event of ventilation system shutdown
of more than 30 minutes and that advising airlines that this should be
done was insufficient to accomplish the committee's objective. FAA, on
the other hand, said that airlines pay close attention to advisories.
The agency decided against issuing a regulation because there are
situations when an evacuation within 30 minutes is not possible due to
operational necessity, such as when a ventilation system breakdown
occurs on a taxiway far from a gate.
Some Technologies Exist for Improving Cabin Air Quality, but There Are
Questions About Whether They Should be Required:
Several technologies exist today that could improve cabin air quality,
but opinions vary on whether requiring the use of improved technologies
in commercial airliner cabins is warranted. We found one of these
technologies, HEPA filters, is strongly endorsed by cabin air quality
and health experts as providing the best possible protection against
one cabin air problem--the presence of particulates, bacteria, and
viruses in recirculated air. While FAA does not currently require HEPA
filters, some health experts believe these filters should be required,
given their demonstrated effectiveness in cleansing cabin air. Figure 3
illustrates a typical HEPA filter for commercial passenger aircraft.
Figure 3: A Typical HEPA Filter for Commercial Passenger Aircraft:
[See PDF for image]
[End of figure]
According to many in the aviation community, several technologies are
available today, and more are in the planning stages, that could
improve the air quality in commercial airliner cabins. However, some in
the aviation industry question whether requiring their use is
warranted. Filtering particulates, bacteria, viruses, and gaseous
pollutants and removing ozone can improve the healthfulness of cabin
air, and increasing cabin humidity and absorbing more cabin odors and
gasses can increase the comfort of passengers and cabin crews. While
aircraft manufacturers acknowledge that a few technologies are
available today that could further improve air quality and comfort in
airliner cabins and that more are possible in the future, they believe
that unless future research proves otherwise, the ventilation systems
in the aircraft they have produced provide ample amounts of relatively
clean air. One technology with proven effectiveness is HEPA filtering
of recycled cabin air. All new large commercial airliners in production
with ventilation systems that recirculate cabin air come equipped with
these filters, which, when properly fitted and maintained, are
effective at capturing airborne contaminants such as viruses that enter
the re-circulation system. However, some regional jets, which have
fewer than 100 seats, are not equipped with filters, and some older
large aircraft still use less efficient filters. FAA does not require
the filtration of recirculated air, but health experts and members of
the committee that produced the 2001 report on cabin air quality
believe that given their proven effectiveness, HEPA filters should be
required for all aircraft that recirculate cabin air. In addition,
airflow rates could be increased in some aircraft by adjusting settings
on the ventilation system, thereby dissipating the effects of some
contaminants. However, this would be done at the expense of higher fuel
consumption, increased engine emissions, and lower cabin humidity.
High Efficiency Particulate Filters Are an Effective Technology for
Cleaning Recirculated Air:
HEPA filters are a readily available and affordable technology for
providing the best possible protection against one cabin air problem--
the presence of particulates, bacteria, and viruses in recirculated
air. However, HEPA filters will not filter gaseous contaminants. These
filters have become widely available for aircraft since the late 1990s.
According to EPA, HEPA filters can remove nearly all particulate
contaminants, such as airborne particles and infectious agents
including bacteria and viruses, from the recirculated air that passes
through them.[Footnote 34] A manufacturer of HEPA filters, as well as
health authorities such as CDC, NIOSH, and WHO, believe that HEPA
filters are highly effective in preventing the transmission of bacteria
and viruses through aircraft ventilation systems. However, they
emphasize that HEPA filters clean only the air that is recirculated
through aircraft ventilation systems, so transmissions from an infected
person to others nearby are still possible.
HEPA filters are available for most large commercial airliners in the
U.S. fleet, but some aircraft with recirculation systems are equipped
with less effective filters. However, not all commercial aircraft
recirculate air through their ventilation systems. For example, some
smaller jets, such as the Boeing 717 and Bombardier CRJ-200s, which
typically fly shorter routes, as well as older models of some longer-
range aircraft, such as the Boeing 737-200 and the DC-10, provide 100
percent outside air to the passenger cabins instead of recirculating
air and, therefore, would not need HEPA filters. Nevertheless, most
commercial airliners in use today recirculate between 30 and 55 percent
of the air provided to the passenger cabin. Officials from Boeing and
Airbus, the world's two largest manufacturers of commercial aircraft,
told us that all their aircraft with recirculation systems currently in
production are equipped with HEPA filters. The ventilation systems in
many older commercial aircraft were designed to use the less effective
filters available at the time, and some of these aircraft still use
these types of filters. However, according to Boeing and Airbus
officials, HEPA filters can be used on these older aircraft with little
or no retrofitting required.[Footnote 35] According to a filter
manufacturer, a HEPA filter costs about twice as much (e.g., $400 to
$600 for the smaller narrow-body aircraft) as the non-HEPA models that
are less effective in trapping particulates. Some regional jets, such
as the Embraer ERJ-145 recirculate air but are not equipped with
filters.
In fact, FAA does not require the filtration of recirculated air on
aircraft. However, when manufacturers voluntarily equip their aircraft
models that recirculate cabin air with HEPA or other filters when they
are certified for flight by FAA, as most do, the aircraft are required
to continue operating with the filters. The schedule for changing the
filters is also included in the FAA certification process. Airlines
typically change HEPA filters after 4,000 to 12,000 hours of service to
maintain good airflow and in accordance with manufacturers'
recommendations.
Little information has previously been available on the extent of HEPA
filter usage in commercial aircraft ventilation systems, though the
Council report and many in the health community have pointed to the
importance of HEPA filters in preventing the spread of bacteria,
viruses, and other contaminants in aircraft cabins. As noted earlier in
this report, the 2001 Council report recommended that FAA investigate
and publicly report on the need for installing equipment to clean the
air supplied to aircraft cabin ventilation systems. In the report, the
committee did not determine how many larger aircraft were equipped with
HEPA filters, and regional jets were not within the scope of its study.
However, the report concluded that HEPA filters are highly effective in
removing all airborne pathogens and other particulate matter that pass
through them. The report further stated that the use of recirculated
air in aircraft cabins when combined with effective HEPA filtration
does not contribute to the spread of infectious agents. Members of the
research community, including those from NIOSH, as well as the
Association of Flight Attendants, have noted that given the proven
effectiveness of HEPA filters in capturing contaminants such as
infectious viruses and bacteria, FAA should require their use on all
aircraft with recirculation systems.
To determine the extent of HEPA filter usage in the United Stares, we
surveyed the largest 14 airlines[Footnote 36] in the United States that
had Airbus, Boeing, or McDonnell Douglas aircraft that recirculate
cabin air, and we received responses from 12 airlines. Of the 3,038
aircraft for which we were able to obtain survey results, 15 percent
(454 aircraft)[Footnote 37] did not use HEPA filters. All of the
aircraft that did not use HEPA filters were older out-of-production
models that used less effective filters. One airline has plans to
retrofit a small number of these aircraft with HEPA filters.
We were also able to obtain some information on HEPA filter usage in
the U.S. regional aircraft fleet by contacting the manufacturers of
these aircraft. We found that 69 percent of these regional aircraft
recycle cabin air (1,087 of 1,584), and only a handful of these
aircraft are equipped with HEPA filters. The manufacturer of a new
regional jet model[Footnote 38] offers HEPA filters as an option.
Information we obtained from two airlines that had 29 of these aircraft
indicated that about half (14 of 29) were equipped with HEPA filters.
We also found that 90 percent of the regional aircraft (973 of 1,087
aircraft) that recycled cabin air would require modifications to be
retrofitted with HEPA filters. Most of these aircraft (73 percent) had
no provision for installing filters in their air ducts.
Consideration has also been given to filtering outside air entering an
aircraft's ventilation system. Outside air at cruise altitudes is
mainly free of pollutants, except for ozone. However, in the event of
an engine or hydraulic system malfunction, outside air can become
contaminated before it enters the ventilation system. In addition, when
an aircraft is at the gate or taxiing, the available outside air
contains pollutants normally present around the airport, including
exhaust from other aircraft on the runway. For these reasons, the 2001
Council report recommended that FAA investigate the need for and
feasibility of installing air-cleaning equipment for removing particles
and vapors from the air supplied to the ventilation system. As
previously noted, FAA has put off consideration of this recommendation
until the completion of FAA's and ASHRAE's air quality research and
surveillance program in 2006 or 2007. One manufacturer did begin
installing outside air filtering equipment on one of its models in
1992. British Aerospace began equipping its BAe 146 aircraft (now out
of production) with outside air filters as part of an effort to reduce
cabin odors. Other manufacturers, including Boeing and Airbus, contend
that outside air filtration is not necessary unless U.S. and European
research indicates a problem with the quality of air entering aircraft
ventilation systems.
Technology is Available to Remove Ozone from the Air Brought in from
Outside the Aircraft:
Technologies are currently available for removing ozone from outside
air. Ozone is present in the air at high altitudes on some routes,
particularly those over the polar regions, and FAA requires that the
airlines that fly these routes take measures to maintain cabin ozone
levels at or below prescribed limits (e.g., using devices that convert
ozone to oxygen). According to ATA officials, nearly all commercial
aircraft that fly on these routes are so equipped. However, the Council
report said that although FAA requires that ozone concentrations in
aircraft cabins be maintained within specified limits, surveillance
programs with accurate and reliable equipment are needed to ensure
compliance and that the ozone converter equipment works properly. One
study attributed elevated ozone levels that exceeded FAA limits to
temporary ozone plumes that can appear unexpectedly. In November 2000,
the British House of Lords, in a study of health issues in aircraft
cabins,[Footnote 39] made a recommendation that airlines fit their
aircraft that fly on routes where these plumes occur with ozone
converters to minimize potential health problems. The Council report
also identified the need for FAA to take effective measures to ensure
that ozone does not exceed levels specified in FAA regulations,
regardless of altitude. As noted earlier, FAA plans to monitor ozone
levels in selected aircraft as part of its surveillance and research
program. However, some committee members told us that the effort will
be too limited to enable FAA to determine if ozone is present on
aircraft not fitted with converters or whether ozone converters are
working properly.
Increasing Ventilation Rates in Aircraft Cabins Poses Challenges:
Increasing ventilation rates on aircraft to levels approximating those
currently required in buildings would pose technological challenges,
and aircraft manufacturers believe such increases are not necessary.
Raising ventilation rates would reduce the effects of some airborne
contaminants by diluting their concentration.
According to Boeing and Airbus officials, airflow rates on their
aircraft could be slightly increased by adjusting settings on the
ventilation systems, but such adjustments would increase fuel
consumption and result in higher operating costs. According to Boeing
officials, to achieve the same airflow rates recommended for buildings,
aircraft ventilation systems, and possibly the aircraft themselves,
would have to undergo expensive modifications. Boeing and Airbus
believe that unless the U.S. and European research and surveillance
initiatives prove otherwise, ventilation rates in commercial aircraft
are sufficient to sustain passenger and cabin crew comfort and health.
Boeing and Airbus officials told us that they are always seeking to
improve the aircraft they build, but they believe that the ventilation
systems in the aircraft they produce provide a healthy and relatively
comfortable environment for passengers and cabin crew. Nevertheless,
Boeing is considering increasing the air pressure and humidity levels
on the 7E7, its proposed long-range, high-altitude aircraft. Airbus
will also offer an improved air ventilation system on its new large
aircraft, the A380. Because of the competitive nature of the aircraft
manufacturing industry, few details are available on the 7E7 and A380
ventilation systems. Boeing and Airbus officials noted that if current
research and surveillance efforts indicate problems with any aspects of
the ventilation systems in their aircraft, they would work toward
developing the necessary technologies to deal with these problems.
Conclusions:
The combined research efforts of FAA and ASHRAE on cabin air quality
will provide a foundation of knowledge, according to some members of
the committee that produced the 2001 Council report on cabin air
quality. However, as currently designed and funded, these efforts may
not answer many long-standing questions about the effect of air quality
on cabin occupants' health and comfort. FAA is attempting to balance
the need to conduct additional research on the healthfulness of cabin
air quality with other research priorities, such as improving passenger
safety. Our prior work on airliner cabin safety and health has
underscored the importance of setting risk-based research priorities,
in part by establishing cost and effectiveness estimates to allow
direct comparisons among competing research priorities. In commenting
on this prior work, FAA cautioned that if too much emphasis is placed
on cost/benefit analyses, potentially valuable research may not be
undertaken. We concur in that caution. However, information on the
nature and extent of health effects from cabin air is needed in order
to identify potential health threats so that it can be determined if
action is warranted to improve cabin air quality and to target research
and development accordingly. Moreover, committee members recommended
more study of these issues, and others in the industry have concerns
about FAA's surveillance and research program as currently conceived.
Committee members were particularly concerned about FAA's decision to
delay action on ensuring that air quality regulations are adequate or
being met on all flights. In addition, the agency's current plan to
monitor cabin air quality on only two aircraft types during part I of
its program will not provide FAA with information that is generalizable
to the U.S. commercial airliner fleet. Thus, key questions that the
agency's research and surveillance program were designed to address
will remain unanswered if part II of FAA's program is not properly
designed and adequately funded. Such information is also needed to
guide the development of new technologies. Given the importance of this
research and surveillance effort, the program needs to be well
designed, properly funded, coordinated with international cabin air
quality research efforts such as those ongoing in Europe and Australia,
and conducted in accordance with accepted standards for independence
and oversight. The Council in its 2001 report recommended that Congress
designate a federal agency to conduct or direct the cabin air quality
research program and recent legislation assigned FAA as the lead
federal agency for this effort. FAA has begun a surveillance and
research program on its own.
Furthermore, FAA has not taken steps to ensure that HEPA filters, which
are a proven technology for eliminating some contaminants such as
viruses and bacteria from recirculated cabin air, are used as widely as
possible on commercial aircraft. FAA does not currently require the use
of filters on recirculated air. Nevertheless, we found that a number of
aircraft manufacturers and airlines voluntarily install them and that
the vast majority of larger commercial aircraft are equipped with HEPA
filters. However, we also found that only a few smaller regional jets
that recirculate cabin air have HEPA or any other type of filters. FAA
has decided to delay addressing the 2001 Council report recommendation
calling for the agency to investigate the need for air cleaning
equipment on aircraft ventilation systems until it completes its cabin
air quality surveillance and research program in 2006 or 2007. FAA
needs to determine the costs and benefits of requiring HEPA filters on
commercial aircraft that recirculate air.
Finally, although FAA has made some progress in implementing the
Council's recommendation regarding the need to increase the
availability of information on health issues related to air travel,
more needs to be done. Creating links on the FAA Web site to pertinent
information on the CDC and WHO Web sites is a good start, but
navigating the FAA's Web site to reach these links is difficult. In
addition to improving the user friendliness of the FAA Web site links,
some commenting committee members suggested that FAA should consider
other methods for disseminating information on the health risks of
flying, such as providing brochures for physicians to use when
discussing these issues with patients.
Recommendations for Executive Action:
To help ensure that FAA's research and surveillance efforts on airliner
cabin air quality answer critical outstanding questions about the
nature and extent of potential health effects of cabin air quality on
passengers and flight attendants, GAO recommends that the Secretary of
Transportation direct the FAA Administrator to:
* develop a detailed plan for the research and surveillance efforts,
including key milestones and funding estimates, in accordance with
generally accepted practices for oversight and independence;
* appoint a committee of acknowledged experts in the fields of aircraft
ventilation and public health, including representatives of EPA and
NIOSH, to assist in planning and overseeing the research and
surveillance efforts recommended by the National Research Council in
2001;
* leverage the findings of international research on airliner cabin air
quality to inform FAA's surveillance and research efforts; and:
* report to Congress annually on the progress and findings of the
research and surveillance efforts and funding needs.
In order to help improve the healthfulness of cabin air for commercial
aircraft passengers and cabin crews, the FAA Administrator should
assess the costs and benefits of requiring the use of HEPA filters on
commercial aircraft with ventilation systems that recirculate cabin
air. If FAA chooses to require the use of HEPA filters, it should also
ensure that the regulation covers the maintenance requirements for
these filters.
In addition, to increase access to information on the health risks
related to air travel, the FAA Administrator should direct the staff
responsible for the FAA Web site to improve the links to other Web
sites containing this information. The Administrator should also
consult with medical associations and health organizations, such as
CDC, on other ways to increase the dissemination of this information.
Agency Comments:
We provided copies of a draft of this report to the Department of
Transportation for review and comment. FAA generally agreed with the
report's contents and its recommendations. The agency provided us with
oral comments, primarily technical clarifications, which we have
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 of this report
to interested congressional committees, the Secretary of
Transportation, and the Administrator, FAA. We will also 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].
Signed by:
Please call me at (202) 512-2834 if you or your staff have any
questions concerning this report. Major contributors to this report are
listed in appendix VI.
Sincerely yours,
Gerald L. Dillingham:
Director, Civil Aviation Issues:
Signed by Gerald L. Dillingham:
[End of section]
Appendixes:
Appendix I: Objectives, Scope, and Methodology:
The Ranking Democratic Member of the Subcommittee on Aviation, House
Committee on Transportation and Infrastructure, asked us to provide
information on steps that the aviation community is taking to address
concerns about cabin air quality. Specifically, our research focused on
the following questions: (1) What is known about the major potential
health effects of air quality in commercial airliner cabins on
passengers and flight attendants? (2) What actions has the National
Research Council recommended to improve cabin air quality, and what is
the status of those actions? (3) What technologies are available today
to improve the air quality in commercial airliner cabins, and which, if
any, should be required?
To answer the first question, we reviewed the December 2001 National
Research Council report on aircraft cabin air quality, which was the
most current and comprehensive examination of the existing literature
on this issue and made recommendations for potential approaches for
improving cabin air quality. We also independently reviewed many of the
studies on issues related to cabin air quality, paying particular
attention to those issued after the publication of the 2001 Council
report.[Footnote 40] We also gathered information from the governments
of Australia, Canada, and the United Kingdom and airlines. We also
interviewed officials representing the Federal Aviation Administration
(FAA), the World Health Organization (WHO), the Centers for Disease
Control and Prevention (CDC), the National Institute for Occupational
Safety and Health (NIOSH), the Aerospace Medical Association (AsMA),
the Air Transport Association (ATA), the Association of Flight
Attendants (AFA), the International Airline Passengers Association
(IAPA), aircraft and air filter manufacturers, as well as experts on
cabin air quality issues, including members of the committee that
produced the 2001 Council report on cabin air quality.
To address the second question, we interviewed Council committee
members about their views on how FAA was addressing the recommendations
they made in their report. Before conducting the interviews, we
provided the committee members with information from FAA on its plans
for addressing the Council's recommendation. We then asked them for
their views on the approach for addressing each of the recommendations.
We conducted interviews with 11 of the 13 committee members; we were
unable to contact 2 members. Of the 11 members we interviewed, 8 agreed
to provide their views on at least some of the recommendations. Three
members declined to address any of the recommendations, saying that
they were outside their fields of expertise and that they had not
followed the progress of FAA's implementation of the recommendations.
To address the third question, we interviewed representatives of
aircraft manufacturers, filter manufacturers, FAA officials, and
experts on aircraft ventilation systems, including members of the
committee. To determine HEPA filter usage, we first identified the 28
airlines that account for 99.94 percent of the revenue passenger miles
(RPM) flown by U.S. airlines as reported in Aviation Daily for May
2003.[Footnote 41] Fourteen of these airlines had aircraft that
recirculate cabin air. The other 14 only had smaller regional aircraft
or larger aircraft that did not recirculate cabin air. After selecting
the 28 airlines, we obtained information from Air Transport World
(Airclaims 2002 data, July 2003 edition) on the number of aircraft they
operate by model type. We then obtained information from the aircraft
manufacturers that allowed us to categorize the 5,354 aircraft in the
28 airlines by whether or not they recycle air (see table 3).
Table 3: Number of Large and Regional Aircraft of Top 28 Airlines That
Do or Do Not Recycle Cabin Air:
Aircraft size: Larger aircraft;
Cabin air recycled: 3,422;
Cabin air not recycled: 348;
Total: 3,770.
Aircraft size: Regional aircraft;
Cabin air recycled: 1,087;
Cabin air not recycled: 497;
Total: 1,584.
Total;
Cabin air recycled: 4,509;
Cabin air not recycled: 845;
Total: 5,354.
Source: GAO.
[End of table]
Larger aircraft included the commercial aircraft manufactured by
Airbus, Boeing, and McDonnell Douglas. Regional aircraft included
Avions de Transport Regional (ATR), British Aerospace (BAe),
Bombardier, Dornier, Embraer, Fokker, Jetstream, and Saab models.
Our primary focus with the larger aircraft was to determine the HEPA
filter usage for the 3,422 larger aircraft that recycled cabin air. To
obtain this information, we surveyed the 14 airlines that had aircraft
in this category and obtained responses from 12 (covering 3,038 of the
3,422 aircraft in this category). Our survey form, which we
administered by e-mail, asked the airlines to provide the following
information: the number of active aircraft by model type as of June 30,
2003; the number of active aircraft with HEPA filters; the number of
active aircraft without HEPA filters; the reasons why HEPA filters are
not used; and, if applicable, the types of filters used if other than
HEPA filters.
Our primary focus with the regional aircraft was to determine what
percentage of these aircraft recycled air, and, for those aircraft that
did recycle air, what percentage would require major modifications to
be retrofitted with a HEPA filter. We were able to make this
determination on the basis of information provided by the
manufacturers. Because only a small portion of the regional aircraft
that recycle air are capable of being fitted with HEPA filters, we did
not survey the 13 airlines that had only regional aircraft. In the
cases where returned surveys also included information on regional
aircraft that could use HEPA filters with little or no retrofitting, we
found that only a small portion were doing so.
[End of section]
Appendix II: Biographical Information on the National Research Council
Committee:
Dr. Morton Lippman: Professor of environmental medicine and director of
the Center for Particulate Matter Health Effects Research and of the
Human Exposure and Health Effects Research Program at New York
University School of Medicine.
Dr. Harriet A. Burge: Associate professor of environmental microbiology
at the Harvard School of Public Health. Dr. Burge's current area of
research is on the role of environmental exposures in the development
of asthma and evaluating exposure to fungi, dust mite, cockroach, and
cat allergens in three separate epidemiology studies assessing risk
factors for the development of asthma.
Dr. Byron Jones: Associate dean for Research and Graduate Programs and
director of the Engineering Experiment Station at the College of
Engineering, Kansas State University. Dr. Jones's research interests
are in heat and mass transfer, human thermal systems simulation, and
thermal measurements and instrumentation.
Dr. Janet M. Macher: Air pollution research specialist with the
Division of Environmental and Occupational Disease Control of the
California Department of Health Services. Her research has focused on
the evaluation of methods to collect and identify airborne biological
material and on engineering measures to control airborne infectious and
hypersensitivity diseases.
Dr. Michael S. Morgan: Professor in the Department of Environmental
Health, Industrial Hygiene and Safety Program of the University of
Washington and director of the Northwest Center for Occupational Health
and Safety. His research is focused on human response to inhalation of
air contaminants, including the products of combustion and volatile
solvents, and has encompassed both ambient air contaminants and
occupational environmental health hazards.
Dr. William W. Nazaroff: Professor of environmental engineering in the
Department of Civil and Environmental Engineering of the University of
California, Berkeley. His main research interest is indoor air quality,
with emphasis on pollutant-surface interactions, transport/mixing
phenomena, aerosols, environmental tobacco smoke, source
characterization, exposure assessment, and control techniques.
Dr. Russell B. Rayman: Executive director of the Aerospace Medical
Association in Alexandria, Virginia, retired from the U.S. Air Force in
1989 with the rank of colonel after a military medical career.
Dr. John D. Spengler: The Akira Yamaguchi Professor of Environmental
Health and Human Habitation and director of the Environmental Science
and Engineering Program at the Harvard School of Public Health. Dr.
Spengler's research is focused on assessment of population exposures to
environmental contaminants that occur in homes, offices, schools, and
during transit, as well as in the outdoor environment.
Dr. Ira B. Tager: Professor of epidemiology in the Division of Public
Health, Biology, and Epidemiology at the University of California,
Berkeley, and is codirector and principal investigator for the Center
for Family and Community Health. Dr. Tager's research includes the
development of exposure assessment instruments for studies of health
effects of chronic ambient ozone exposure in childhood and adolescence,
the effects of ozone exposure on pulmonary function, and the effects of
oxidant and particulate air pollution on cardio-respiratory morbidity
and mortality and morbidity from asthma in children.
Dr. Christiaan Van Netten: Associate professor in the Department of
Health Care and Epidemiology at the University of British Columbia and
head of the Division of Occupational and Environmental Health. Dr. Van
Netten's research interests include environmental toxicology and the
use of electrodiagnostics to monitor worker exposure to agents that
affect the peripheral nervous system.
Dr. Bernard Weiss: Professor of environmental medicine and pediatrics at
the University of Rochester School of Medicine and Dentistry. His
special interest and publications lie primarily in areas that involve
chemical influences on behavior, including the neurobehavioral
toxicology of metals such as lead, mercury, and manganese.
Dr. Charles J. Weschler: Adjunct professor in the Department of
Environmental and Community Medicine at the University of Medicine and
Dentistry of New Jersey, Robert Wood Johnson Medical School/Rutgers.
His research interests, among others, include chemical interactions
among indoor pollutants and the chemistry of the outdoor environment as
it impacts the indoor environment.
Dr. Hanspeter Witschi: Professor of toxicology and associate director of
the Institute for Toxicology and Environmental Health at the University
of California, Davis. Dr. Witschi's research interests include
experimental toxicology, biochemical pathology, and the interaction of
drugs and toxic agents with organ function at the cellular level.
Source: National Research Council.
[End of section]
Appendix III: Transmission of Severe Acute Respiratory Syndrome (SARS)
on Board Aircraft Is Rare and Associated with Proximity:
Aboard aircraft, cabin occupants are confined in close quarters for
extended periods and can be exposed to infectious diseases carried by
other occupants. Because air travel is rapid, people can complete their
journeys before the symptoms of a disease begin. Consequently, there
has been much concern regarding the in-flight transmission of
contagious diseases, particularly tuberculosis and, more recently,
severe acute respiratory syndrome (SARS). As part of our review of
airliner cabin air quality, we tracked the status of SARS and air
travel.
SARS is a serious respiratory illness that has affected persons in
Asia, North America, and Europe. According to the World Health
Organization (WHO), as of September 26, 2003, there were an estimated
8,098 probable cases reported in 27 countries, including 29 cases in
the United States. There have been 774 deaths worldwide, none of which
have occurred in the United States. The Centers for Disease Control and
Prevention (CDC) believes SARS is caused by a previously unrecognized
coronavirus.[Footnote 42] The symptoms of SARS can include a fever,
chills, headache, other body aches, and a dry cough.
SARS appears to be transmitted by close personal contact, which
includes touching the eyes, nose, or mouth after touching the skin of
infected individuals or objects that have been contaminated with
infectious droplets released by an infected individual while coughing
or sneezing. People with SARS pose the highest risk of transmission to
household members and health care personnel in close contact. Most
cases of SARS involved people who cared for or lived with someone with
SARS or had direct contact with objects contaminated with infectious
droplets. Information to date suggests that people are most likely to
be infectious when they have symptoms such as fever or cough. However,
it is not known how long before or after their symptoms begin that
people with SARS might be able to transmit the disease to others. Most
of the U.S. cases of SARS have occurred among travelers returning to
the United States from other parts of the world affected by SARS, such
as China. According to WHO, as of September 26, 2003, the latest
probable case of SARS reported in the United States was on July 13,
2003. However, there is no evidence that SARS is spreading in the
United States. WHO has reported that although the global outbreak of
SARS has been contained, considerable uncertainty surrounds the
question of whether SARS might recur, perhaps according to a seasonal
pattern. Several respiratory illnesses occur much less frequently when
temperature and humidity are high and then return when the weather
turns cooler. WHO has also requested all countries to remain vigilant
for the recurrence of SARS and to maintain their capacity to detect and
respond to the reemergence of SARS, should it occur. The CDC has
conducted broadcasts over the Internet for healthcare providers on
preparing for the return of SARS.
WHO has reported that as of May 23, 2003, there have been 29 probable
cases of in-flight SARS transmissions on four flights worldwide. Out of
the 29 cases, 24 were on one flight, and 4 of the 29 cases were flight
attendants. WHO has stated that since then there have been no reported
cases of in-flight SARS transmissions. The WHO Director of Communicable
Diseases stated there is a very low risk of catching SARS on an
airplane through the airplane's ventilation system. He noted that
nearly all of the in-flight transmissions occurred between passengers
who were sitting near each other. This official also stated that
airport screening procedures have been effective in keeping individuals
displaying SARS symptoms from boarding aircraft. In October 2003, WHO
issued a report in which it did not find evidence that SARS is an
airborne disease. This report further stated that at all outbreak sites
the main route of transmission was direct contact, via the eyes, nose,
and mouth, with infectious respiratory droplets.
In December 2003, the New England Journal of Medicine published the
results of a study on the transmission of SARS on three flights that
transported at least one person who had SARS.[Footnote 43] The study
found that on one flight carrying four people with SARS symptoms, one
other person at most developed the disease, and no illness was
documented on another flight transporting a person with presymptomatic
SARS. However, on a third flight carrying a symptomatic person, 22
probable cases of SARS[Footnote 44] occurred among the other 119
passengers. According to the study, for the 22 people with illness, the
mean time from the flight to the onset of symptoms was four days, and
there were no recognized exposures to persons with SARS before or after
the flight. The study found that illness in passengers was related to
the physical proximity to the person with SARS on the flight. Illness
was reported in 8 of the 23 passengers seated in the three rows in
front of the person with SARS, as compared to 10 of the 88 passengers
seated elsewhere on the aircraft. The study noted however, that 90
percent of the passengers who became ill on the flight were seated more
than 36 inches from the person with SARS, which had been the cutoff
used to define the spread of SARS droplets in other investigations. The
study authors speculated that "airborne, small particle, or other
remote transmission may be more straightforward explanations for the
observed distribution of cases." The study concluded that SARS
transmissions may occur on flights carrying people in the symptomatic
stages of the disease and that measures to reduce the risk of
transmission are warranted.
In November of 2003, more than 50 leading SARS researchers from 15
countries concluded that a safe and effective vaccine would be an
important complement to existing SARS control strategies. Most of the
experts agreed, however, that a SARS vaccine will not be available in
time, should an epidemic reoccur in the near future. A WHO official
stated that the licensing and commercialization of a SARS vaccine could
probably not be realized in 2004.
According to the International Air Transport Association (IATA),
passengers are not at risk from being infected with the SARS virus from
the cabin crew, who must be medically fit, without SARS symptoms, and
physically capable to fly and fulfill their duties. CDC has stated that
there is currently no evidence that a person can be infected with SARS
from handling baggage or goods, because the primary means of infection
is close personal contact. CDC has also stated the transmission of SARS
has been associated with close contact with people with SARS symptoms,
such as passengers on an aircraft.
The CDC has issued travel alerts and advisories for travel to areas
affected by SARS. A travel advisory recommends that nonessential travel
be deferred; in contrast, a travel alert informs travelers of the
health concern and provides advice about specific precautions. The CDC
recommends that if SARS is suspected in an outpatient setting,
healthcare providers should provide and place a surgical mask over the
person's nose and mouth. The CDC further recommends that if this is not
feasible, the person with SARS should be asked to cover his/her mouth
with a disposable tissue when coughing, sneezing, or talking. WHO has
urged airport officials in countries affected with SARS outbreaks to
take precautionary screening measures, such as asking passengers if
they have had contact with anyone who has had the disease. U.S.
airlines that fly to Asia report that they are following CDC and WHO
guidelines. FAA has links to the CDC and WHO guidelines on its Web
site. U.S. airlines that do not fly internationally are not modifying
their procedures because they see no SARS risk to cabin occupants.
According to ATA officials, U.S. airlines that do not fly
internationally were not advised by CDC to modify procedures because
there was no evidence of community transmission of SARS in the United
States. However, all ATA-member airlines cooperated fully with CDC in
instances where there was a possible person with SARS who might have
transferred from an international to a domestic flight.
[End of section]
Appendix IV: European CabinAir Study: Scope and Methodology:
In 2001, Building Research Establishment, Ltd. (BRE)[Footnote 45]
initiated a study on cabin air quality that was estimated to cost $8
million. The following link provides the official description of the
effort as posted on BRE's Internet site: [Hyperlink, http://
projects.bre.co.uk/envdiv/cabinair/work_programme.html]:
To further the industry's understanding of what is known about air
quality issues by assessing the current level of air quality found in
aircraft cabins, BRE will monitor four generic aircraft types in flight
and assess cabin air quality and ventilation system performance,
including the effects of passenger density and flight duration. A total
of 50 such flights are planned. The findings will identify current best
practice and will be used to improve understanding of (1) what
constitutes good cabin air; (2) the impact on the safety, health, and
comfort of passengers and cabin crew; and (3) the effects on operating
costs, fuel energy use, and the external environment.
To identify the technology (i.e., environmental control systems
including filtration and air distribution) that is available to improve
cabin air quality, BRE will develop new designs to address various air
quality issues, including the control of carbon dioxide,
humidification, outside air supply, and the recirculation and
filtration of air. Operating costs and energy consumption will be
analyzed in relation to environmental impacts. New designs must be
suitable for retrofitting to existing aircraft, either as complete
environmental control systems or as subsystems within existing units.
The overall intention is to make environmental control systems flexible
and easy to operate. For example, improved systems might enable the
crew to match the system to the passenger load factor, reduce bleed
air, or provide additional comfort in different areas of the cabin.
BRE will seek to improve the performance of filtration systems and then
develop new technologies and systems. It will assess existing
filtration systems and consider how the installation process and
activities such as maintenance, lifting, and cleaning affect
performance. A technology demonstrator rig will be developed to test
new filtration systems. New and enhanced features will be developed to
mitigate such problems as the recirculation of pollutants, bacteria,
and viruses. Other major factors include the compatibility of the
filtration systems with the overall environmental control system,
operational costs, and energy consumption.
The effectiveness of current air distribution systems will be gauged
through in-flight monitoring. New design strategies and technologies,
such as personal controls, will be developed with the goal of
maximizing the effectiveness of cabin ventilation. The study will also
look at ways of making the distribution system more easily integrated
with aircraft design.
To assess and determine potential improvements to existing standards
and performance specifications for the cabin environment, BRE will
assess existing standards. Potential improvements to existing standards
and specifications will be determined. Checks will be carried out to
ensure the feasibility of the performance specifications and costs and
to identify any environmental implications. New performance indexes and
comfort criteria will also be defined, and BRE will develop a model to
be tested.
[End of section]
Appendix V: Surveillance and Research Programs:
Key recommendations of the Council report were to establish
surveillance and research programs to determine effects of cabin air
quality on aircraft occupants' health and comfort.
Surveillance Program:
The following is a detailed description of these programs as stated in
the Council report.
Surveillance program objectives:
* To determine aircraft compliance with existing Federal Aviation
Regulations (FARS) for air quality.
* To characterize accurately air quality and establish temporal trends
of air-quality characteristics in a broad sample of representative
aircraft.
* To estimate the frequency of nonroutine operations in which serious
degradation of cabin air quality occurs.
* To systematically document health effects or complaints of passengers
and crew related to routine conditions of flight or air-quality
incidents; to be effective, this effort must be conducted and
coordinated in conjunction with air-quality monitoring.
Surveillance program approach:
* Continuously monitor and record ozone, carbon monoxide, and carbon
dioxide, fine particles, cabin pressure, temperature, and relative
humidity.
* Sample a representative number of flights over a period of 1 to 2
years.
* Continue to monitor flights to ensure accurate characterization of
air quality as new aircraft come online and aircraft equipment ages or
is upgraded.
* Conduct a program for the systematic collection, analysis, and
reporting of health data with the cabin crew as the primary study
group.[Footnote 46]
Research Program:
The following is a detailed description of the research program,
including long-standing questions regarding air quality, objectives,
and program approach.
Outstanding air quality-related questions to be addressed by the
research program:
* How is the ozone concentration in the cabin environment affected by
various factors (e.g., ambient concentrations, reaction with surfaces,
the presence and effectiveness of catalytic converters) and what is the
relationship between cabin ozone concentrations and health effects on
cabin occupants?
* What is the effect of cabin pressure altitude on susceptible cabin
occupants, including infants, pregnant women, and people with
cardiovascular disease?
* Does the environmental control system (ECS) provide sufficient
quantity and distribution of outside air to meet the FAA regulatory
requirements, and to what extent is cabin ventilation associated with
complaints from passengers and cabin crew? Can it be verified that
infectious disease agents are transmitted primarily between people who
are in close contact? Does recirculating cabin air increase cabin
occupants' risk of exposure?
* What is the toxicity of the constituents or degradation products of
engine lubricating oils, hydraulic fluids, and de-icing fluids, and is
there a relationship between exposures to them and reported health
effects on cabin crew? How are these oils, fluids, and degradation
products distributed from the engines into the ECS and throughout the
cabin environment?
* What are the magnitudes of exposures to pesticides in aircraft
cabins, and what is the relationship between the exposures and reported
symptoms?
* What is the contribution of low relative humidity to the perception
of dryness, and do other factors cause or contribute to the irritation
associated with the dry cabin environment during flight?
Research program objectives:
* To investigate possible association between specific air quality
characteristics and health effects or complaints.
* To evaluate the physical and chemical factors affecting specific air
quality characteristics in aircraft cabins.
* To determine whether FARS for air quality are adequate to protect
health and ensure the comfort of passengers and crew.
* To determine exposure to selected contaminants (e.g., constituents of
engine oils and hydraulic fluids, their degradation products, and
pesticides) and establish their potential toxicity more fully.
Research program approach:
* Use continuous monitoring data from surveillance program when
possible.
* Monitor additional air quality characteristics on selected flights as
necessary (e.g., integrated particulate-matter sampling to assess
exposure to selected contaminants).
* Identify and monitor "problem" aircraft and review maintenance and
repair records to evaluate issues associated with air quality
incidents.
* Collect selected health data (e.g., pulse-oximetry data to assess
arterial oxygen saturation of passengers and crew).
* Conduct laboratory and other ground-based studies to characterize air
distribution and circulation and contaminant generation, transport, and
degradation in the cabin and the ECS.
[End of section]
Appendix VI: GAO Contacts and Staff Acknowledgments:
GAO Contacts:
Gerald L. Dillingham, (202) 512-2834 Beverly L. Norwood, (202) 512-
2834:
Staff Acknowledgments:
In addition to the individuals named above, Kevin Bailey, Jim Geibel,
David Ireland, Bert Japikse, Stanley Kostyla, Edward Laughlin, Donna
Leiss, and Maria Romero made key contributions to this report.
[End of section]
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[End of section]
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FOOTNOTES
[1] Although airliners are pressurized, the air pressure in an aircraft
cabin is lower than it is at sea level. Airliners are required to be
pressurized to an altitude that is not higher than 8,000 feet. This is
about three-fourths the air pressure at sea level.
[2] According to the World Health Organization (WHO), there is a very
low risk of catching SARS through an airplane's ventilation system.
SARS is believed to be transmitted based on proximity to an infected
individual. However, WHO reported that as of May 23, 2003, there were
29 probable cases of in-flight SARS transmissions on four flights. See
appendix III for more information on SARS.
[3] The National Research Council is the principal operating arm of the
National Academy of Sciences and the National Academy of Engineering.
[4] National Research Council. The Airliner Cabin Environment and the
Health of Passengers and Crew, National Academy Press (Washington,
D.C.: Distributed electronically December 2001; bound report
copyrighted 2002).
[5] See the Selected Bibliography at the end of this report and, in
particular, Hocking, Martin B., "Trends in Cabin Air Quality on
Commercial Aircraft: Industry and Passenger Perspectives," Reviews on
Environmental Health 17, 1 (2002): 1-49; and Rayman, Russell B., "Cabin
Air Quality," Aviation, Space and Environmental Medicine 73 (2002):
211-215.
[6] The NRC committee consisted of 13 members. We attempted to contact
all 13 members. We interviewed 11, and 8 members responded to cabin air
quality questions and the implementation status of their
recommendations. Of the 11 committee members interviewed, 3 declined to
address our questions, stating that they did not follow the progress of
FAA's implementation of the recommendations. For example, 1 member
stated that as a toxicologist, he could not comment on the overall
approach FAA is taking to address the NRC recommendations.
[7] For purposes of this report, we use the Environmental Protection
Agency's definition of HEPA, which is a filtering efficiency of 99.97
percent.
[8] Of the 11 members interviewed, 8 agreed to address our questions
concerning the committee recommendations (see app. I).
[9] National Research Council, The Airliner Cabin Environment: Air
Quality and Safety, National Academy Press (Washington, D.C.: 1986) and
National Research Council, The Airliner Cabin Environment and the
Health of Passengers and Crew, National Academy Press (Washington,
D.C.: Distributed electronically December 2001; bound report
copyrighted 2002).
[10] The 2001 Council study reported that the effects of ozone vary
with latitude, altitude, and season and that the concentration of ozone
is much higher at cruise altitudes in high latitudes (greater than
approximately 60°N) than at low latitudes (approximately 30°N),
resulting in higher concentrations of ozone on polar flights.
[11] FAA does not require these filters; however, our survey of U.S.
airlines found that 85 percent of the large aircraft (those that carry
100 passengers or more) currently use HEPA filters.
[12] The American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE) advances the arts and sciences of
heating, ventilation, air conditioning, refrigeration, and related
human factors to serve the evolving needs of the public.
[13] According to FAA officials, FAA regulations have always required
limitations on certain contaminants (e.g., carbon monoxide and carbon
dioxide). Later amendments added ozone and changed the ventilation
requirements. However, these officials stressed that airplanes are
certified to the regulations in effect at a certain time prior to their
manufacture. Only the latest certified airplanes will have had to meet
the latest amendment level for the regulations governing the cabin
environment, such as a 1996 amendment which added the requirement that
each occupant be provided with 0.55 pounds (equivalent to 10 cubic
feet) of fresh air per minute under standard operating conditions.
[14] ATA officials noted that these symptoms are also consistent with a
host of other causes, such as lack of sleep (perhaps due to difficulty
in adjusting to different time zones), dehydration (possibly from
drinking too much caffeine or alcohol and not enough water during a
long flight), the effect of changes in climate, or exposure to
contaminants in other settings.
[15] The Wendell H. Ford Aviation Investment and Reform Act for the
21st Century (AIR-21), Public Law 106-181, April 5, 2000.
[16] The environmental control system includes devices that pressurize
the cabin in flight, control thermal conditions in the cabin, and
ventilate the cabin with outside air to prevent a buildup of
contaminants that might cause discomfort or present a health hazard.
[17] The ventilation rate is the flow of outside air supplied to the
cabin for ventilation and it does not normally include recirculated air
even though recirculated air may be used for cabin ventilation.
[18] According to FAA officials, a comparison of ventilation rates for
buildings and aircraft is not valid and that "sick building syndrome"
should not be applied to aircraft. Furthermore, both FAA and Boeing
officials told us that the new ASHRAE standards for buildings create
two sets of building standards for ventilation--one for high density
buildings and another for low density buildings. Boeing officials said
that under this standard, high density buildings would have lower
airflow rates per occupant, and that high density buildings are most
comparable to airplanes with high density occupancy.
[19] Disinsection is the process of spraying the aircraft cabin with
insecticide to prevent the conduction of insects such as mosquitoes
from one country to another. The spraying is often done while
passengers and crewmembers are still on board. The United States
terminated this practice in 1979 because of health concerns and doubts
about the effectiveness of the spraying. Over the years, a number of
countries have changed their policies regarding the spraying of
pesticides. The Department of Transportation is studying alternative
technological methodologies, including air curtains to prevent airborne
insects from flying into the aircraft cabin.
[20] World Health Organization, Tuberculosis and Air Travel: Guidelines
for Prevention and Control (Geneva, Switzerland: Aug. 27, 2003).
[21] Zitter, Jessica, Peter Mazonson, Dave Miller, Stephen Hulley, and
John Balmes, "Aircraft Cabin Air Recirculation and Symptoms of the
Common Cold," Journal of the American Medical Association 288 (2002):
483-486.
[22] Olsen, Sonja J. et al., "Transmission of the Severe Acute
Respiratory Syndrome on Aircraft," The New England Journal of Medicine
349; 25 (2003): 2416-2422.
[23] U.S. General Accounting Office, Aviation Safety: Advancements
Being Pursued to Improve Airliner Cabin Safety and Health, GAO-04-33
(Washington, D.C.: October 3, 2003).
[24] Vision 100--Century of Aviation Reauthorization Act,'' passed by
Congress in November 2003, requires that FAA, at a minimum: 1) conduct
surveillance to monitor ozone in the cabin on a representative number
of flights and aircraft to determine compliance with existing
regulations for ozone, 2) collect pesticide exposure data to determine
exposures of passengers and crew, 3) analyze samples of residue from
aircraft ventilation ducts and filters after air quality incidents to
identify potential exposure of contaminants to passengers and crew, 4)
analyze cabin air pressure and altitude, and 5) establish an air
quality incident reporting system. The FAA administrator is to report
the findings to Congress no later than 30 months after the date of the
act's enactment.
[25] NIOSH conducted the study over 2 years on 33 commercial flights on
10 different types of airplanes owned by four air carriers. NIOSH
initially surveyed female flight attendants on reproductive health, but
the survey was later expanded to include respiratory effects. The study
did not include direct linkage to measurement of cabin environment
conditions. The survey respondents flew on a wide variety of aircraft
in which the cabin environment was not sampled.
[26] Circadian rhythm is the body's internal resting or wakefulness
schedule over the course of a day. Outside influences, such as jet lag,
can disrupt the circadian rhythm temporarily.
[27] FAA's fiscal year 2004 facilities and equipment budget includes
$8.5 million to develop and demonstrate a chemical/biological detection
and mitigation capability and decontamination procedures for aircraft
occupants and for returning the aircraft to service.
[28] The minimum number of flights to be included will depend on the
recommendations of part I and on the availability of research funds and
will be specified in the solicitation for part II to be released by
ASHRAE in the future.
[29] The European cabin air study is known as CabinAir.
[30] Building Research Establishment, Ltd. (BRE) is a high-level
research-based consultancy organization, owned by a not-for-profit
entity headquartered in the United Kingdom. BRE provides the aviation
industry with expert advice on cabin environment issues and,
particularly, on air quality in passenger aircraft.
[31] In addition to Europe's cabin air study (CabinAir), Australia has
addressed cabin air quality issues through the creation of a Reference
Group on Cabin Air Quality. The Reference Group is responsible for
following the progress of and analyzing the outcomes of international
research and development. The Reference Group comprises government
agencies, industry representatives, employee/union representatives,
and representatives of aircraft and engine manufacturers.
[32] The flight attendant groups have actively lobbied for independent
research that is not funded and controlled by companies that have a
financial interest in the outcome.
[33] ASHRAE writes standards and guidelines in its fields of expertise
to guide industry in the delivery of goods and services to the public.
Currently, it has some 87 active standards and guideline project
committees, addressing such broad areas as indoor air quality, thermal
comfort, energy conservation in buildings, reduction of refrigerant
emissions, and the designation and safety classification of
refrigerants.
[34] The Environmental Protection Agency states that HEPA filters are
to be 99.97 percent efficient for the removal of Particulate Matter
(PM) that is greater than or equal to 0.3 micrometer (mm) in diameter.
[35] Installing HEPA filters on the A300 would require some
modification.
[36] We used revenue passenger miles (RPM) as reported in Aviation
Daily for May 2003 to identify the largest U.S. carriers. This list
identified the largest 28 airlines, 14 of which had the larger aircraft
that recirculate cabin air. The other 14 airlines only had smaller
regional aircraft or larger aircraft that did not recycle cabin air. An
RPM is a standard unit of passenger demand for air transport, defined
as one fare-paying passenger transported one mile. We obtained the
model information for these carriers from data published in Air
Transport World (July 2003).
[37] We obtained information on 3,038 larger aircraft that recycled
cabin air, 454 of which did not have a HEPA filter. We were not able to
obtain survey results for another 384 aircraft. Of these 384, 56 (15
percent) of the aircraft were older models that most airlines had not
retrofitted with HEPA filters. Our study included 3,770 larger
aircraft, of which 348 did not recycle cabin air.
[38] HEPA filters are available for the CRJ700 manufactured by
Bombardier.
[39] The House of Lords, Select Committee on Science and Technology,
Air Travel and Health, 5th Report HL.
[40] See the Selected Bibliography at the end of this report and, in
particular, Hocking, Martin B., "Trends in Cabin Air Quality on
Commercial Aircraft: Industry and Passenger Perspectives," Reviews on
Environmental Health 17, 1 (2002): 1-49; and Rayman, Russell B., "Cabin
Air Quality," Aviation, Space and Environmental Medicine 73 (2002):
211-215.
[41] A revenue passenger mile is a standard unit of passenger demand
for air transport, defined as one fare-paying passenger transported one
mile.
[42] A coronavirus is so named because it looks like a corona or halo
when viewed under an electron microscope. Two human coronaviruses cause
about 30 percent of common colds. Coronavirses have been found to
infect cattle, pigs, horses, turkeys, chickens, cats, dogs, rats, and
mice.
[43] Olsen, Sonja J. et al., "Transmission of the Severe Acute
Respiratory Syndrome on Aircraft," The New England Journal of Medicine
349; 25 (2003): 2416-2422.
[44] According to the study, laboratory confirmed SARS developed in 16
persons, 2 others were given diagnosis of probable SARS and four were
reported to have SARS but could not be interviewed by the study team.
WHO reported that as of May 23, 2003, 24 probable SARS transmissions
occurred on this flight. The study does not indicate the reason for the
discrepancy.
[45] Building Research Establishment, Ltd. (BRE) is a high-level
research-based consultancy organization, owned by a not-for-profit
entity headquartered in the United Kingdom. BRE provides the aviation
industry with expert advice on cabin environment issues and
particularly on air quality in passenger aircraft.
[46] On March 4, 2003, FAA announced the creation of a voluntary
program for air carriers, called the Aviation Safety and Health
Partnership Program. Through this program, the agency intends to enter
into partnership agreements with participating air carriers, which
will, at a minimum, make data on their employees' injuries and
illnesses available to FAA for collection and analysis.
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