美国环境保护署（US EPA）多年来一直试图设定饮用水中氡的最高污染物水平（MCL）。1991年7月18日，美国环保局提出了包括氡在内的六种放射性核素的国家初级饮用水法规。为回应这一提议而提交的600多套公开评论中，大多数集中在氡方面。美国环保署提议的饮用水中氡的MCL为300 pCi/L，受到了严厉批评。州卫生和辐射保护机构、科学界、供水商和其他联邦政府机构普遍认为，美国环保局高估了与拟议MCL相关的增量效益，同时低估了合规成本。 1992年11月公众评论期结束后，美国环保局开始评估该提案，并准备对评论作出回应，以制定最终规则。人们仍然担心拟议的氡MCL的合理性。在提出建议时，美国环境保护局根据一项法院命令，不迟于1993年4月公布最终放射性核素规则。本文重点介绍了自拟议规则发布以来的发展和历史。包括25个参考文献和表格。

The US Environmental Protection Agency (US EPA) has been attempting for several years to set a maximum contaminant level (MCL) for radon in drinking water. On July 18, 1991, US EPA proposed National Primary Drinking Water Regulations for six radionuclides, including radon. Most of the more than 600 sets of public comments submitted in response to this proposal focused on radon. US EPA's proposed MCL of 300 pCi/L for radon in drinking water has received severe criticism. There is widespread agreement among state health and radiation protection agencies, the scientific community, water suppliers, and other federal government agencies that the US EPA has overestimated the incremental benefits associated with the proposed MCL, while it has underestimated the cost of compliance. Following the close of the public comment period in November 1992, US EPA began to evaluate the proposal and prepare a response to the comments in order to develop a final rule. Concern remains regarding the rationality of the proposed MCL for radon. At the time of proposal, USEPA was under a court order to publish the final radionuclides rule no later than April 1993. This article focuses on developments and chronological history since the proposed rule was published. Includes 25 references, tables.