Steroid hormones and certain pharmaceuticals have been reported in U.S. waters for over 40 years. Early reports demonstrating that certain hormones and pharmaceuticals were not completely eliminated by wastewater treatment did not gain significant attention until the 1990s when reports of reproductive disorders in fish were linked to trace contaminants in wastewater outfalls. Treatment efficacy for these emerging contaminants varies widely depending on unit processes, operational parameters, and compound structure. A study was undertaken in 2002 to evaluate the occurrence and fate of pharmaceuticals in U.S. drinking water systems. From the 20 drinking water systems evaluated, the five most prevalent pharmaceuticals detected in raw water were carbamazepine, dilantin, sulfamethoxazole, ibuprofen, and meprobamate. However, in finished water the occurrence pattern shifted based on treatment processes and operational conditions. A similar study was launched in 2006 with the investigation of 19 U.S. drinking water facilities. This study unveiled similar findings for pharmaceutical occurrence. The most prevalent pharmaceuticals detected in U.S. drinking water were the anti-anxiety pharmaceutical meprobamate, the anti-epileptic drug dilantin, and the anticonvulsant carbamazepine. Despite the use of ultra-trace analytical methods, steroid hormones used as pharmaceuticals were not detected in U.S. drinking water. Pharmaceuticals have more robust human health data than essentially all other environmental contaminants due to extensive clinical testing. Thus, research to date suggests that concentrations of pharmaceuticals in U.S. drinking water are far below any human health relevance..