Perchlorate levels rise in winter

Friday, Jan. 9, 1998 | 10:40 a.m.

Recent high levels of perchlorate found in Las Vegas drinking water are being blamed on temperature changes at Lake Mead.

In July, samples collected by the Southern Nevada Water Authority registered 11 parts per billion of perchlorate in both raw lake water and in treated drinking water.

By December, those levels rose to 16 parts per billion in raw lake water and 14 parts per billion in treated water.

But that's well below the levels which affect human health, according to studies collected from human use of the chemical. Scientists have reported perchlorate has been tracked in people treated for overactive thyroid glands.

Perchlorate, a rocket fuel booster made at two industrial plants near Henderson for 40 years, was first detected in August, said Kay Brothers, resources director for the Southern Nevada Water Authority.

The Nevada Division of Environmental Protection traced the source of the perchlorate to Kerr-McGee Corp. and American Pacific Co., formerly Pacific Production and Engineering Co., which moved its operation to Cedar City, Utah, after an explosion at its local plant in May 1988.

Groundwater contaminated from making the substance that boosts oxygen in rocket fuel is seeping into the Las Vegas Wash.

The Las Vegas Wash, six miles upstream from the Las Vegas Valley's drinking water intake pipeline, has introduced perchlorate into the lake ranging from less than 4 parts per billion to 16 parts per billion, depending on the time of year, Brothers said.

A part per billion represents less than a teaspoonful of a chemical in water filling two Olympic-sized swimming pools.

"The one thing perchlorate has done is provide a tracer to see how Lake Mead behaves," Brothers said.

In summer, when the lake's temperature rises, groundwater, surface runoff and sewage effluent ride the heat and stay near the surface, she explained.

Lake Mead's water typically turns over once a year around September or October. That's when perchlorate and other things such as bacteria, chemicals, toxins and pesticides mix throughout the body of water.

Once the water is fully mixed in winter, perchlorate levels rise, including the water collected at the drinking water pipeline, Brothers said.

In the spring as surface temperatures increase, the lower zone remains cold and the wash runoff rides on the top of the cooler water, closer to the surface.

Less than 5,000 parts per billion perchlorate does not interfere with a human thyroid picking up iodine, according to federal Environmental Protection Agency research. That measure equals 10 milligrams per day for an average person drinking about two quarts of water per day.

At 50,000 parts per billion, the perchlorate would prevent the thyroid gland from accepting iodine. In a human being, 100 milligrams per day is a standard dose for blocking iodine to the thyroid when the grand overacts.

Perchlorate can affect bone marrow at 300,000 parts per billion. It would take 600 milligrams per day if a person drank about two quarts of water to affect the bone marrow.

California discovered perchlorate in water wells and in the Colorado River last year, after a test for finding levels in the parts per billion.

California environmental officials set a guideline of 18 parts per billion of the chemical in drinking water. There are no federal standards or state rules for limiting perchlorate in drinking water.

Since then, a number of studies are under way to determine how dangerous perchlorate may be in drinking water.

The U.S. Air Force is investigating perchlorate levels in rats to define when harmful effects occur. The study should be completed in May and a final report is expected in September.

Both Kerr-McGee and American Pacific are testing soil and water wells on and off their property located on a Clark County island in Henderson. Those tests should be complete by May, said Allen Biaggi of the Nevada Division of Environmental Protection.

A final report that will lead to an action plan to remove the perchlorate from the Las Vegas drinking water supply and supervised by NDEP should be ready by September, Biaggi said. Removal could begin by December.

Removing perchlorate from the Las Vegas Wash and Lake Mead won't be easy. Reverse osmosis can take the salt from the water.

Some researchers are studying bioremediation, a biological technique to gobble up the perchlorate.

The American Waterworks Association is also funding research to remove perchlorate, which has become a nationwide problem since its discovery in California and Nevada.

Kennecott Copper Co., east of Salt Lake City, discovered perchlorate in its wells in November and put 1,000 employees on bottled water. The contamination is coming from a neighboring industrial site.

Perchlorate is formed by combining ordinary salt and chlorine and heating it. The ammonium perchlorate is formed by adding ammonia to the process.