During the reclamation of a Superfund site located along the Colorado front range, an employee of a private company contracted by the U.S. Department of Energy began setting off radiation security alarms while entering the facility. After months of investigation to determine the source of this radiation, it was discovered that the drinking water from the individual's private well was so highly contaminated with radon that simply showering with this water left enough radiation on his body to trigger the alarms.
The purpose of our study was to identify and evaluate the potential extreme occurrence of natural radon contamination in private well water sources in this rural Colorado mountain community.
Review of Literature
Radon and Health
Radon is a well-established human carcinogen and is the principal source of radioactivity exposure among the general population in most countries around the world (Catelinois et al., 2006). For many years scientists have sought to assess cancer risk associated with long-term radon exposure, and in 2005, the U.S. surgeon general issued a national health warning reporting that radon causes at least 20,000 lung cancer deaths per year in the U.S. and that all homes should be tested for elevated levels (Catelinois et al., 2006; U.S. Environmental Protection Agency [U.S. EPA], 2010). Also, in 1998, the International Agency for Research on Cancer declared radon as a group I carcinogen in humans based on results from animal and human epidemiological studies (Catelinois et al., 2006).
Occupational and Residential Exposure
The first evidence of the relationship between radon exposure and lung cancer was observed in occupational studies of miners exposed to high levels of radon underground (Al-Zoughool & Krewski, 2009; Cothern & Smith, 1987; Graves, 1987; Levy, 2009). Decades of subsequent research assessing this association has been firmly established and many cohort studies have shown statistically significant positive associations between radon inhalation and the risk of developing lung cancer (Darby et al., 1995; Howe, Nair, Newcombe, Miller, & Abbatt, 1986; Kusiak, Ritchie, Muller, & Springer, 1993; Laureir et al., 2004).
Many studies have also been conducted in estimating the risk of residential radon exposure among the general population showing a reasonable risk between such exposure and the development of lung cancer (Alavanja, Lubin, Mahaffey, & Brownson, 1999; Auvinen et al., 1996; Barros-Dios, Barreiro, Ruano-Ravina, & Figuerias, 2002; Catelinois et al., 2006; Darby et al., 1998; Pearce & Boyle, 2005; Wichmann et al., 2002, 2005). In one study, the risk of lung cancer associated with residential radon exposure examined a collaborative analysis of individual data obtained from 13 case-control studies related to lung cancer and residential radon. It was found that cases of lung cancer increased as the level of radon exposure in the home increased with a linear dose-response relationship (Darby et al., 2005).
Radon and Drinking Water
Because radon is completely soluble in water, high concentrations of radon can accumulate in groundwater and pose a potential health risk for those who use it for drinking and domestic purposes (Al-Zoughool & Krewski, 2009; Cothern & Rebers, 1991; Cothern & Smith, 1987; Graves, 1987; National Research Council [NRC], 1999a). In fact, one environmental radon assessment study found that private well water supplies in the U.S. were as much as 3-20 times higher in radon concentrations compared to that of public drinking water systems (Hess, Horton, Prichard, & Coniglio, 1985).
At increased concentrations, radon-contaminated water used for drinking and domestic purposes can contribute to the added radon concentrations in a home (Collman, Loomis, & Sandler, 1991; Cothern & Smith, 1987; Graves, 1987; NRC, 1999a; Prichard, 1987). With agitation and heating, radon in water is released into the air and scientists have estimated that 10%-15% of total radon in air may actually be attributed to radon off-gassing from domestic water (Collman et al., 1991). Also, the ingestion of high concentrations of radon in drinking water represents a particular concern for the stomach and gastrointestinal tissues, and scientists have estimated that up to 90% of the ingested dose of radon is delivered directly to the stomach tissue (Kendall & Smith, 2002). In fact, it has been estimated that radon in drinking water causes approximately 168 cancer deaths per year--89% from lung cancer caused by breathing radon released to the indoor air from the water, and 11% from stomach cancer caused by the ingestion of radon-contaminated water (NRC, 1999a, 1999b; U.S. EPA, 2012).
Radon Regulatory Limitations
In comparison to other group I carcinogens, radon health and safety regulations tend to lack in overall progress and backing within the U.S. Currently, no federal regulations exist for radon exposure in indoor air; however, U.S. EPA has set a recommended action limit of 4 picocuries per liter (pCi/L) (U.S. EPA, 2011a). Similarly, no federally enforced standards currently exist that protect individuals from radon-contaminated drinking water. In 1991, the U.S. EPA did propose to regulate radon levels in public drinking water supplies; however, this regulation has yet to be adopted and would not include oversight for private wells (Abdallah, Habib, Nuwayhid, Chatila, & Katul, 2007; NRC, 1999b; U.S. EPA, 2011b). In this 1991 proposal, U.S. EPA proposed a new National Primary Drinking Water Regulation that recommended a maximum contaminant level (MCL) of 300 pCi/L. In addition to the proposed MCL, U.S. EPA also proposed a debated alternative MCL (AMCL) of 4,000 pCi/L. This AMCL would be allowed only if states or the local community water system developed a U.S. EPA-approved indoor air quality program, also called multimedia mitigation programs, to educate and provide radon consultation to area residents. Overall, this AMCL is often referred to as a mechanically influenced standard as opposed to a relevant health protection standard (Abdallah et al., 2007; NRC, 1999b; U.S. EPA, 2011c).
Sample, Instrumentation, and Data Collection
The population in our study was considered a convenience sample of 29 private wells located in a rural Colorado mountain community. A total of 27 wells were sampled in our study.
All water samples were sent to a local U.S.EPA-certified laboratory for analysis. The laboratory used the Standard Method of the Examination of Water and Wastewater 7500-Rn Liquid Scintillation Method, which is specific for determining radon concentrations in drinking water obtained from ground or surface water sources (Clescerl, Green berg, & Eaton, 1999).
Water sampling occurred over a...