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In 1996, feral carp from the Las Vegas Wash and Las Vegas Bay were reported to have significantly different plasma sex steroid and vitellogenin levels than carp collected from a reference site in Callville Bay. These types of endocrine disruptive effects have been associated with estrogenic substances found in wastewater effluents. Furthermore, concentrations of some synthetic organic chemicals were found to be greater in water, sediment, and fish tissues from the Las Vegas Wash and Las Vegas Bay when compared with similar samples from the Callville Bay reference site. For these reasons, various studies were initiated to determine what compounds may be impacting the aquatic environment of the Las Vegas Bay, whether the effects documented in feral fish could be reproduced in fish caged at the same sites, and the source(s) of these xenobiotic compounds. In 1997, toxicity identification and evaluation methodology was used to screen the waters of Lake Mead, including raw and finished drinking water, for estrogenic and dioxin-like compounds. Organic compounds were extracted from water samples using solid-phase extraction. The corresponding organic extracts were separated into fractions based on polarity. Each extract and fraction was tested for estrogenicity using a mammalian breast carcinoma cellular bioassay. This cellular bioassay is extremely sensitive to estrogen. Once extracts or fractions exhibiting estrogenic activity were identified, they were separated into finer fractions and again tested using the bioassay. This bioassay-directed fractionation and subsequent instrumental analysis allowed for mass-balance evaluation. Various analytical instrumentation was used to identify and quantitate the organic compounds present. Although no significant bioactivity was detected in any drinking water samples, significant estrogenicity was observed in water samples from the Las Vegas Wash and Las Vegas Bay. Results of the bioanalyses are discussed in this paper. In 1998, a larger study began which included the extraction of 100 liter water samples and caging of "control" fish at various sites in Lake Mead. Instrumental analyses were expanded to include high-resolution mass spectrometry for identification of compound previously unreported in Lake Mead. DDT, DDE, and DDD (collectively, DDTs) and four isomers of hexachlorocyclohexane (HCH) were detected at some sites, with concentrations ranging from less than detection to 28 ng/L. Alkylphenolic compounds were detected in some samples, with concentrations ranging from less than detection to 1500 ng/L. Caffeine, nicotine, oxybenzone, N,N-diethyl-meta-toluamide (DEET), phosphate-based flame-retardants, and several pharmaceuticals were detected in some samples with concentrations ranging from less than detection to 360 ng/L. The identities of several of these previously unreported compounds were verified using high-resolution mass spectrometry. Furthermore, laboratory fish caged in Las Vegas Bay showed statistically significant differences in reproductive physiology from fish caged at the reference sites. Recently, the Southern Nevada Water Authority (SNWA) has initiated several new studies related to these emerging contaminants. Research has begun to investigate drinking water treatment strategies for these compounds. Initial results have shown activated carbon and ozone to be effective at removing selected endocrine disruptors and pharmaceuticals from water. Additionally, new analytical equipment has been purchased to more accurately and sensitively identify these emerging contaminants in water. Includes 7 references, figures.

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Edition: Vol. - No. Published: 06/16/2002 Number of Pages: 4File Size: 1 file , 350 KB