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The Environmental Protection Agency (EPA) has been working to promulgate a drinking water rule on radon for more than a decade. As with many other rules, the debate focuses on whether science proves that the rule is necessary to protect public health, given its very high costs, particularly to rural America. Costs to small communities may force them to make huge sacrifices. The only solution for such communities might be to discontinue drinking water service, which could lead residents to turn to dangerous sources such as untreated surface waters.

The drinking water standard for most regulated substances is specified as a “maximum contaminant level” or MCL. The MCL sets the maximum amount of a substance that the EPA will allow in tap water. Currently, EPA regulations set a MCL of 4,000 picocuries per liter for radon. In 1991, the EPA proposed changing the MCL to 300 picocuries per liter on the basis of 1991 findings of an agency report on radon. Because of controversies regarding EPA science and the potential costs of the rule, Congress placed a hold on the EPA’s promulgation of the rule until it reauthorized the SDWA. But rather than reining in the EPA and preventing it from setting a ridiculously stringent standard, the 1996 SDWA amendments required the agency to issue a final rule within four years after reviewing the findings of a government-funded National Academy of Sciences (NAS) risk assessment of radon. An affiliate of the NAS—the National Research Council (NRC)—produced a report in 1998.2 The EPA proposed a rule in 1999, again suggesting an MCL of 300 picocuries per liter. However, under the 1996 SDWA amendments, the EPA rule would allow localities and states to meet a less stringent standard if they used programs to regulate radon in indoor air. Despite a mandate to finalize the rule in 2002, the EPA has not yet produced a final rule.