Biological monitoring of uranium exposure in south central Virginia

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 microg/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 study. 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 microg/g creatinine to 0.011 microg/g creatinine in 1 year. Comparatively, NHANES has reported that the geometric mean for all participants, ages 6 years and older, is 0.008 microg/g creatinine, with the 95th percentile being 0.040 microg/g creatinine. None of the second round specimens showed a urine uranium concentration higher than baseline for an individual.