Chemicals polluting Lake Mead

By Mary Manning (contact)

Tuesday, Nov. 19, 1996 | 11:59 a.m.

Federal and state agencies announced increased pollution monitoring in Lake Mead, the primary drinking water supply for Las Vegas, after two studies released today showed deformed carp in the lake's waters.

Organic chemicals from treated and untreated wastewater, pesticides and chemicals were discovered in the water, bottom sediment and the fish in the Las Vegas Wash and Las Vegas Bay where 125 million gallons a day of treated sewage flow from the Las Vegas Valley.

U.S. Geological Survey officials, who conducted the studies, cautioned that while the findings are important, they can't begin to answer questions about human health.

"These findings suggest the potential for a significant problem," USGS chief biologist Dennis Fenn said.

But Alan O'Neill, superintendent of the Lake Mead National Recreation Area, said, "We want to stress that Lake Mead has outstanding water quality."

"What these results show is that we will need to do additional studies with the participation of other entities in the Las Vegas Valley to determine when and where deterioration occurred or is presently occurring and what actions are needed to improve water quality in Las Vegas Wash before it enters Lake Mead."

Treated and untreated wastewater flows from the Las Vegas Valley down the Las Vegas Wash into Lake Mead. Downstream, water is piped from the lake, treated and used as drinking water in the valley.

Some critics say the fast-growing valley has sent too much polluted water into the lake, opening the door to infectious diseases getting into the drinking water.

Based on the carp samples, the Nevada Division of Wildlife with the National Park Service are providing samples of two sport fish -- striped bass and catfish -- for chemical analysis. Results will not be available for up to four months.

Samples from the Colorado, Virgin and Muddy rivers to Lake Mead as well as more from Las Vegas Wash taken in 1996 have not been analyzed yet.

Pollutants found in the carp do not exceed U.S. Food and Drug Administration standards, O'Neill said. An advisory group of state and federal health officials has been formed to review the results and advise on what further studies or actions may be required.

USGS scientists presented their findings from two studies that focused on carp from 25 sites around the nation as part of the National Water Quality Assessment Program.

The study put a collecting bag in a stream of water for five weeks, gathering chemicals, explained Kay Brothers, director of the Southern Nevada Water Authority's Resources Department.

"We are talking to the USGS about a cooperative study in various parts of the lake, Brothers said. "We test the water for the Safe Drinking Water Act. We have not seen anything above detection of those contaminants."

Carp feed at the bottom of lakes, exposing them to contaminants found in the water, sediments and food.

The studies do not indicate the source of the contaminants. However, there is a growing body of scientific evidence links the compounds to disruption in animal reproductive systems.

Called endocrine disrupters, the compounds scramble the genetic material in cells, causing feminine traits in male animals and a drop in sperm.

Some of the compounds, formed from common household and industrial chemicals, could elevate the risk of cancer in humans if consumed in sufficient quantities over time.

In fact, people may have more to fear from endocrine disrupters from drinking polluted water, according to a scientist with the World Wildlife Fund, Theo Colburn. People don't tend to eat the contaminated parts of fish, he said.

Lake Mead's water quality could get worse as explosive growth continues to add more wastewater to it, former UNLV biologist and lake expert Larry Paulson said. The water authority is building a 9-foot-wide pipeline to bring Nevada's full share of the Colorado River to the Las Vegas Valley.

archive