Source water for 15 community-water-system (CWS) wells in the vicinity of Dayton, Ohio, was sampled to evaluate the occurrence of 258 anthropogenic compounds (AOCs). At least one AOC was detected in 12 of the 15 samples. Most samples contained a mixture of compounds (average of four compounds per sample). The compounds that were detected in more than 30 percent of the samples included three volatile organic compounds (VOCs) (trichloroethene, chloroform, and 1,1,1-trichloroethane) and four pesticides or pesticide breakdown products (prometon, simazine, atrazine, and deethylatrazine). In general, VOCs were detected at higher concentrations than pesticides were; among the VOCs, the maximum detected concentration was 4.8 ?g/L (for trichloroethene), whereas among the pesticides, the maximum detected concentration was 0.041 ?g/L (for atrazine).
During a later phase of the study, samples of source water from five CWS wells were compared to samples of finished water associated with each well. In general, VOC detections were higher in finished water than in source water, primarily due to the occurrence of trihalomethanes, which are compounds that can form during the treatment process. In contrast, pesticide detections were relatively similar between source- and finished-water samples.
To assess the human-health relevance of the data, concentrations of AOCs were compared to their respective human-health benchmarks. For pesticides, the maximum detected concentrations were at least 2 orders of magnitude less than the benchmark values. However, three VOCs - trichloroethene, carbon tetrachloride, and tetrachloromethane - were detected at concentrations that approach human-health benchmarks and therefore may warrant inclusion in a low-concentration, trends monitoring program.