Grand Rounds: Nephrotoxicity in a Young Child Exposed to Uranium from Contaminated Well Water

Groundwater is the principal source of drinking water for 14–15 million (14%) of the 105.5 million homes in the United States and for approximately 42 million people [Centers for Disease Control and Prevention (CDC) 2003; U.S. Census Bureau 2000; U.S. Environmental Protection Agency (EPA) 2006]. Groundwater is at risk of contamination by a wide variety of industrial pollutants and naturally occurring toxic chemicals. Industrial chemicals that have been identified in ground-water include benzene, methyl tert-butyl ether, nickel, perchlorate, perchloroethylene, pesticides, phenol, and trichloroethylene [Agency for Toxic Substances and Disease Registry (ATSDR) 1996, 1997a, 1997b, 1998, 2005b, 2005c; Baker et al. 1978; U.S. EPA 2006]. These contaminants are most commonly found near chemical and pesticide production facilities, hazardous waste sites, roads, and railways. Naturally occurring toxic chemicals that have been documented in groundwater include arsenic, manganese, radon, and uranium (ATSDR 1999, 2005a;U.S. EPA 2006). These materials may be present in especially high concentrations in mining districts, but also occur widely in certain geologic formations, especially in mountainous areas of the United States (U.S. EPA 2006; Walsh 2003). Private wells that tap groundwater have been associated with episodes of human exposure to toxic chemicals (U.S. EPA 2006). Private wells in the United States are largely exempt from state and federal drinking water regulations, and thus in most states they are not subject to much of the mandatory testing that is required of public water supplies under the provisions of the Safe Drinking Water Act Amendments of 1996 (1996). In most locations, well water is routinely tested only for pH, bacteria, and a small number of chemical contaminants. Uranium is not commonly among the chemicals tested. Because of increasing urban sprawl with continuing movement of populations from urban centers to previously rural areas that lack public water supplies (Frumkin et al. 2004), a growing number of private wells are being drilled in the United States. Unless changes are mandated in current testing requirements, the number of people at risk of exposure to toxic chemicals in groundwater will therefore likely increase. Exposures to chemical contaminants in groundwater have caused disease and disability in exposed populations. The prevalence and severity of these effects reflect the intensity, the duration, and the developmental timing of exposure. Reported health effects have included diminished intelligence after prenatal exposures to lead and manganese; peripheral vascular disease and skin cancer after childhood exposure to arsenic; and fatal methemoglobinemia after exposure in infancy to nitrates (Ahsan et al. 2006; Campbell 1952; Needleman et al. 1979). Infants and young children are especially vulnerable to chemical contaminants in drinking water. This heightened vulnerability reflects the disproportionately great water consumption of young children, who drink 7 times as much water per kilogram body weight per day as the average adult (Ershow and Cantor 1989) (Figure 1). It also reflects the inherent biological vulnerability of the young, which is a consequence of their rapid growth and development and their relative inability to detoxify and excrete many exogenous chemicals [National Research Council 1993]. Figure 1 Mean daily intake of total water per unit of body weight by age group and sex. Figure reprinted from Ershow and Cantor (1989), with permission from Life Sciences Research Office. We present a case of a family who was exposed to naturally occurring uranium in groundwater from their private well in Connecticut. Although all family members had evidence of exposure, the only family member with evidence of nephrotoxicity was the youngest child.