Pharmaceuticals and personal care products in the waters of Lake Mead, Nevada

Several recent reports have indicated that a variety of pharmaceuticals and personal care products are entering the aquatic environment via wastewater discharges. The Boulder Basin of Lake Mead, Nevada, receives a significant input of highly treated wastewater from the Las Vegas Wash. The objectives of the studies presented here were to determine which compounds entering Lake Mead may be able to induce endocrine disruptive effects on aquatic life and to identify previously unreported xenobiotic compounds. Various locations in the Las Vegas Wash and Boulder Basin were investigated between 1997 and 1999. Certain pesticides, polychlorinated biphenyls (PCBs), alkylphenols (APs), polycyclic aromatic hydrocarbons (PAHs), and steroids were target compounds. In the first tier of this research, genetically engineered cell lines were used to screen for estrogenic compounds in organic extracts of Lake Mead water samples. Radioimmunoassay was used to identify and quantitate natural and synthetic estrogens. Bioassay-directed fractionation and mass-balance were used to determine which xenoestrogens exhibited the greatest potency in an estrogen-sensitive cell line. This work demonstrated that natural and synthetic estrogens within the mixture of organic compounds extracted from Lake Mead water samples were responsible for the greatest induction in the estrogen-responsive cellular bioassay. Detectable concentrations ranged from 0.2 - 0.5 and 0.2 - 3 ng/L for ethynylestradiol (EE2) and 17β-estradiol (E2), respectively. The second tier of analysis involved the extraction of 100 L of water followed by gas chromatography with mass selective detection. This methodology was used to identify and quantify known organic compounds and to screen for previously unreported compounds. High-resolution mass spectrometry was used to identify and verify several polar organic compounds that have not previously been reported to be present in Lake Mead. Compounds identified include APs, pharmaceuticals, caffeine, nicotine, flame-retardants, and insect repellants. Detectable concentrations of pharmaceuticals and personal care products ranged from 1 - 1500 ng/L. Concentrations of xenobiotics were greater in samples collected near the confluence of the Las Vegas Wash with Lake Mead at the Las Vegas Bay.