In May 2004, two groundwater wells in Dinwiddie County, Virginia were found to have natural uranium levels either at or above the EPA recommended limit of 30 mg/l. As a result, a stop drinking water advisory was issued until a water treatment system could be installed to remove the uranium. In response to residents' concerns, and uncertainty of exposures, affected individuals were asked to participate in a voluntary epidemiological investigation of uranium uptake and 1-year uranium retention

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... dy. This study had two primary objectives: quantification of the uranium load on the participants, as expressed by their urine uranium concentration, and retention after 1 year of no exposure. A first-morning void urine specimen, along with survey information, was collected from 156 participants in May 2004, with a second collection occurring 12 months later of 91 participants. The samples were analyzed for uranium by ICP/MS, pH, creatinine by the Jaffe method, and RBP by LIA after both collections. A reduction of one order of magnitude for the geometric mean urine uranium concentration was observed, from 0.100 mg/g creatinine to 0.011 mg/g creatinine in 1 year. Comparatively, NHANES has reported that the geometric mean for all participants, ages 6 years and older, is 0.008 mg/g creatinine, with the 95th percentile being 0.040 mg/g creatinine. None of the second round specimens showed a urine uranium concentration higher than baseline for an individual.