Radon in Water

Abstract

AbstractSome groundwater contains the naturally occurring radioactive gas, radon‐222 (radon). Radon dissolved in groundwater is released into indoor air when plumbed in water is agitated indoors. Radon released from domestic water typically contributes less than 2% of total indoor radon. This article describes the health risks from radon in domestic water and the efforts within the United States to regulate radon in drinking water. The U.S. National Research Council (NRC) found that the primary health risks from radon in domestic water are lung cancer and stomach cancer, primarily to ever‐smokers. Radon concentration in air could reach levels considered unsafe for underground miners at some water treatment facilities that aerate water as part of the treatment process. Inhalation of radon gas and its progeny may result in lung cancer (inhalation risk). An estimated 11% of the health risk is from direct ingestion of radon dissolved in drinking water (ingestion risk). The NRC found that radon is a greater source of cancer risk than any other regulated chemical in drinking water. Some ecological studies contradict using the linear nonthreshold (LNT) model to assess the health risks from exposure to radon at low levels typical of indoor air. The U.S. Environmental Protection Agency (EPA) relied on the LNT model to assess health risks and propose standards and goal for radon in drinking water. Some water utilities could opt for treatment to comply with the radon in drinking water standard. Some other water utilities might avoid treatment by adopting a multimedia approach to radon mitigation. The multimedia approach could be more cost‐effective and achieve greater health risk reduction. Noneconomic considerations may influence that decision. Health risk reduction and cost analyses (HRRCA) suggest that most of the benefits would accrue to ever‐smokers and smaller water systems could incur most of the costs.