What were the results of the screening level assessment for placing findings in the context of human health?
One sample from each of 3,497 domestic and public wells was analyzed for 55 volatile organic compounds (VOCs). At least one VOC was detected in about 15 percent of all well samples above a threshold of 0.2 part per billion. Eight of the 55 VOCs had concentrations greater than human-health benchmarks in about 1 percent of all drinking-water supply well samples; these concentrations may be of potential human-health concern if the water were to be ingested without treatment for many years. Most of the detections greater than benchmarks were attributed to the fumigant dibromochloropropane (DBCP) (in domestic wells only) and to the solvents trichloroethene (TCE) and perchloroethene (PCE) in samples from both domestic and public wells. VOC concentrations were less than human-health benchmarks in most of the well samples, indicating that adverse effects are unlikely to occur, even if water with such concentrations were to be ingested over a lifetime. Seventeen VOCs may warrant further investi
