Radiation StandardsScientific Basis Inconclusive, and EPA and NRC Disagreement Continues Gao ID: T-RCED-00-252 July 18, 2000
U.S. regulatory standards to protect the public from radiation lack a conclusively verified scientific basis. In the absence of conclusive data, scientists have assumed that even the smallest radiation exposure carries a risk. Some scientists say that this "linear, no-threshold hypothesis" is too conservative. The National Academy of Sciences plans to conclude its study on the risks of low-level radiation in 2001. The Department of Energy began a 10-year research project on the effects of low-level radiation on human cells, in part to help verify or disprove the linear model. The Environmental Protection Agency (EPA) and the Nuclear Regulatory Commission (NRC) have sometimes differed over how restrictive U.S. radiation protection standards should be, particularly about the proposed disposal of high-level nuclear waste in a repository at Yucca Mountain and the cleanup and decommissioning of nuclear facilities. For example, EPA applies community drinking water limits for radioactive substances to groundwater at nuclear sites; some limits are equivalent to fractions of a millirem a year. NRC includes groundwater and other potential contamination sources under a less restrictive limit of 25 millirem a year for all means of exposure, which conforms with internationally recommended radiation protection guidance. Although the National Academy of Sciences has criticized EPA's approach, it recognizes that EPA has the authority to set a separate standard for Yucca Mountain. As for nuclear cleanup and decommissioning sites where both agencies have jurisdiction, little progress has been made to finalize a memorandum of understanding between the two, and Congress may need to help resolve the agencies' disagreement. Costs per site could be immense, and the tighter the restriction, the higher the cost of cleanup. This testimony summarizes the June 2000 report, GAO/RCED-00-152.
GAO noted that: (1) U.S. radiation standards for public protection lack a conclusively verified scientific basis, according to a consensus of recognized scientists; (2) below certain radiation exposure levels, the effects of radiation are unproven, despite many years of research efforts; (3) evidence of these effects is especially lacking at regulated public exposure levels--levels of 100 millirem a year and below from human-generated sources; (4) at these levels, scientists and regulators assume radiation effects according to what is commonly known as the "linear no threshold hypothesis," or model; (5) according to this model, even the smallest radiation exposure carries a cancer risk, and risks double as the exposure doubles; (6) research into low-level radiation effects continues, including studies attempting to statistically correlate natural background radiation levels in the United States and around the world with local cancer rates; (7) lacking conclusive evidence of low-level radiation effects, U.S. regulators have in recent years set sometimes differing exposure limits; (8) in particular, EPA and NRC appear no closer to agreeing on exposure limits today than in 1994; (9) the two agencies continue to favor different policies and regulatory approaches for various nuclear cleanup and waste disposal applications, especially those relating to groundwater protection; (10) the disagreement involves EPA- and NRC-preferred protection levels that are both well below the range where radiation effects have been conclusively verified; (11) in this regard, the disagreement essentially involves policy judgments and has complicated efforts to clean up facilities, as well as planning for the prospective Yucca Mountain, Nevada, high-level waste repository; (12) costs of implementing radiation protection standards at nuclear cleanup and waste disposal facilities vary from site to site; (13) long-term overall costs could be immense, although these costs have not been comprehensively estimated; (14) an indication of the potential costs is that agencies, especially the Department of Energy, expect to fund hundreds of billions of dollars in nuclear cleanup and waste disposal projects over many years in the future; (15) differences in the costs of the EPA and NRC regulatory approaches to radiation protection have not been comprehensively estimated; (16) however, agency analyses indicate that more restrictive radiation standards cost more to implement, as might be expected; and (17) these analyses also generally show accelerating costs to achieve the most restrictive protection levels.