Grand rounds: nephrotoxicity in a young child exposed to uranium from contaminated well water.

CONTEXT: Private wells that tap groundwater are largely exempt from federal drinking-water regulations, and in most states well water is not subject to much of the mandatory testing required of public water systems. Families that rely on private wells are thus at risk of exposure to a variety of unmeasured contaminants.

CASE PRESENTATION: A family of seven--two adults and five children--residing in rural northwestern Connecticut discovered elevated concentrations of uranium in their drinking water, with levels measured at 866 and 1,160 microg/L, values well above the U.S. Environmental Protection Agency maximum contaminant level for uranium in public water supplies of 30 microg/L. The uranium was of natural origin, and the source of exposure was found to be a 500-foot well that tapped groundwater from the Brookfield Gneiss, a geologic formation known to contain uranium. Other nearby wells also had elevated uranium, arsenic, and radon levels, though concentrations varied widely. At least one 24-hr urine uranium level was elevated (> 1 microg/24 hr) in six of seven family members (range, 1.1-2.5 microg/24 hr). To assess possible renal injury, we measured urinary beta-2-microglobulin. Levels were elevated (> 120 microg/L) in five of seven family members, but after correction for creatine excretion, the beta-2-microglobulin excretion rate remained elevated (> 40 microg/mmol creatinine) only in the youngest child, a 3-year-old with a corrected level of 90 microg/mmol creatinine. Three months after cessation of well water consumption, this child's corrected beta-2-microglobulin level had fallen to 52 microg/mmol creatinine.

SIGNIFICANCE: This case underscores the hazards of consuming groundwater from private wells. It documents the potential for significant residential exposure to naturally occurring uranium in well water. It highlights the special sensitivity of young children to residential environmental exposures, a reflection of the large amount of time they spend in their homes, the developmental immaturity of their kidneys and other organ systems, and the large volume of water they consume relative to body mass.