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.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 350 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 4 |
| Published : | 06/16/2002 |
