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Abstract: Between 1997 and 2002, 16 cases of acute childhood leukemia were diagnosed in children who either lived in Churchill County, Nevada at the time of diagnosis or had lived in the county before their diagnosis. The cases were characterized as a cluster of like illnesses and the probability of having such a cluster occur by chance was estimated to be very small (approximately one in 2.33×108). This suggested that the cluster could be linked to one or more physical, limnological, chemical, or biological agents. This review discusses the setting in which the cluster took place, the epidemiological investigations carried out by the Nevada Bureau of Health Protection Services, the National Center for Environmental Health Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registry, and subsequent investigations supported by a special allocation of federal funds through the US Environmental Protection Agency’s Region IX office in San Francisco, CA. This review is meant as background for the papers in this special issue that report results from multi- and interdisciplinary research into environmental and biological factors potentially related to the Churchill County leukemia cluster. [Copyright &y& Elsevier]

Churchill County, Nevada, has approximately 23,000 residents, among whom an estimated 13,500 relied on private wells for water supply in 2002. This study examined exposure to arsenic in water supplies among residents with private domestic wells and factors related to householder choice to consume tap water. It compared opinions and concerns about water quality with consumption habits and observed concentrations from tap water samples. The results from 351 households indicated that a majority (75 percent) of respondents consumed tap water and that a minority (38 percent) applied treatment. Approximately 66 percent of those who consumed tap water were exposed to concentrations of arsenic that exceeded 10 ppb. Water consumption was related to application of treatment. Among 98 respondents who were not at all concerned about the health effects of aqueous arsenic, 59 (60 percent) reported consuming tap water with concentrations of arsenic exceeding 10 ppb. Conversely, among 86 respondents who were highly concerned about arsenic, 33 (37 percent) consumed tap water with concentrations of arsenic exceeding 10 ppb. Results from a national sampling effort showed that 620 of 5,304 private wells sampled (11.7 percent) had arsenic concentrations above 10 ppb. The paradox of awareness of arsenic in water supplies coupled with consumption of aqueous arsenic in concentrations greater than 10 ppb may be common in other parts of the nation. Enhanced educational efforts, especially related to tap water sampling and explanations of efficacy of available treatment, may be useful means of reducing exposure through private water supplies. [ABSTRACT FROM AUTHOR]

In many rural areas domestic drinking water needs are met by a mixture of public water supplies and private water supplies. Private supplies are not subject to the regulations and management requirements of the Safe Drinking Water Act (SDWA). Amendments to the SDWA recently lowered the standard for arsenic from 50 to 10 ppb in public water supplies (effective in 2006). Churchill County, Nevada, has approximately 25,000 residents. Slightly more than half (13,500) rely on private domestic wells for water supply. Ample data and media publicity about high arsenic concentrations in water supplies and a federally led investigation of a Ieukaemia cluster suggested that residents of the county would be aware that arsenic concentrations in private wells were highly likely to exceed the 10 ppb standard. A survey carried out in 2002 showed that a majority of respondents (72%) consumed water from private wells and among them a minority (38%) applied treatment. Maximum, median and minimum concentrations of arsenic from all samples (n = 351) were 2,100, 26 and <3 ppb, respectively. Seventy-four per cent of all samples exceeded 10 ppb. A majority (87%) of those who applied treatment consumed tap water. The relatively low rate of application of treatment suggested that these rural residents did not recognize that consumption could have associated health risks. However, those who applied treatment were ∼0.3 times as likely to be consuming water with > 10 ppb arsenic than those who consumed water that was not treated. in areas where concentrations of arsenic have been demonstrated to be high, it may be important to conduct a focused educational effort for private well owners to ensure that they take the steps needed to assess and reduce risks associated with contaminants found in tap water, including arsenic. An educational effort could include promoting sampling efforts to determine the magnitude of arsenic concentrations, explaining the risk associated with arsenic consumption and providing information about choices for home treatment systems that are likely to be effective in removing arsenic. This may be especially important in rural areas where adverse health effects are not evident to local populations. [ABSTRACT FROM AUTHOR]