Summary: 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.
