Monday, July 16, 2001 | 10:56 a.m.
Millions of Americans may be exposed to a potentially toxic rocket fuel booster that has been found in Las Vegas Valley drinking water, according to a study released today.
The report by the nonprofit Environmental Working Group shows drinking water of more than 7 million Californians and millions of other Americans is tainted with perchlorate, a chemical found to affect human thyroids.
The greatest danger is to bottle-fed infants, the study says, because a greater portion of their daily diet comes from tap water.
Officials discovered perchlorate in Lake Mead, Southern Nevada's major drinking water source, in 1998 after California health authorities created a test that could detect small amounts of the chemical. It was found in 58 public water systems in that state. Since then, 17 other states have found it.
The group's 50-page report, "Rocket Science: Perchlorate and the Toxic Legacy of the Cold War," noted that in every place where scientists have tested for perchlorate, it has been detected. The federal Environmental Protection Agency believes that contamination exists wherever the rocket fuel or rockets were made or tested -- 39 states in all -- the group says.
The research was reviewed by Dr. Thomas Zoeller of the University of Massachusetts, Boston, who also served as a reviewer for the Environmental Protection Agency.
Neither the federal government nor state officials in Nevada and California have established safety limits on perchlorate in drinking water.
However, the EPA is studying perchlorate to determine its toxicity, said Kevin Mayer at EPA's San Francisco office, and has set a preliminary safety standard of 32 parts per billion in drinking water while studies continue.
Southern Nevada Water Authority officials in December found the highest level ever detected in local drinking water -- 24 parts per billion -- and stopped pumping from Lake Mead, using reservoirs and ground water for more than a week until the perchlorate level dropped to 11 parts per billion.
Perchlorate competes with and replaces iodides in the thyroid gland and breast tissue, medical research shows.
Too much perchlorate can damage the thyroid gland, which controls growth, development and metabolism. Fetuses, infants and children with thyroid damage may suffer mental retardation, loss of hearing, speech defects or poor motor skills. At higher levels of exposure, perchlorate is known to cause cancer.
When infants are fed with formula mixed with tap water, they can receive much larger doses of perchlorate, the study's principal author Bill Walker said. Most of the studies and exposure estimates are based on adult doses.
An 11 1/2-pound infant drinking about a quart of formula made from perchlorate-laced tap water a day would consume concentrations of 40 parts per billion, enough to affect the thyroid, the study concluded. Almost 40 percent of infants in the U.S. drink formula with tap water for the first four months of life, the report noted.
A 1999 study in Arizona comparing infants in Flagstaff consuming water free of perchlorate, and Yuma, which is supplied by perchlorate-laced water from the Colorado River, found changes in the Yuma babies' thyroids.
Perchlorate was suspected of causing cancer in 1966, when the first long-term study of its effects in drinking water was conducted. After two years of being fed perchlorate, more than a third of lab animals developed benign thyroid tumors, compared with none of the control animals. Perchlorate did not directly cause cancer, but induced tumors resulting from hormone changes, the study found.
Scientists did not begin to examine potential health effects of perchlorate at low doses until 1995, when the EPA found that lab animals developed thyroid disorders at low levels.
There have been at least three studies showing no effect from drinking perchlorate-laced water, but they were all sponsored by defense or aerospace contractors, the Environmental Working Group said.
Perchlorate has been made in Henderson since the 1950s for boosting fuel performance in rockets and the space shuttle. It is also used in fireworks, fertilizers and dynamite.
Kerr-McGee Chemical Corp. is working with the Nevada Division of Environmental Protection to remove perchlorate from entering Lake Mead. American Pacific Co., formerly known as Pacific Engineering and Production Co., also manufactured ammonium perchlorate in Henderson, but after an explosion in May 1988, moved its operations to Cedar City, Utah.
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