4 February 2003
Perchlorate, a rocket fuel ingredient, enters Lake Mead near Las Vegas. California is concerned about its effect on drinking water.
A toxic rocket fuel ingredient that is polluting the Colorado River -- the main water source for millions of Californians and most of the nation's winter lettuce -- may be dangerous to public health even at extremely low levels, state and federal environmental officials now believe.
The U.S. Environmental Protection Agency and the California Office of Environmental Health Assessment, which are independently working to set the nation's first enforceable regulations on ammonium perchlorate, are concluding from a number of new studies that the substance could lead to health problems, even in trace amounts.
Those findings present a serious environmental problem for the Southwestern United States, because the entire lower Colorado River is polluted with small amounts of perchlorate from a now-closed Nevada rocket fuel factory.
California officials first discovered the contamination five years ago, and an effort has been underway since then to stem the pollutant's flow from a desert wash near the factory into Lake Mead. But more than 500 pounds of perchlorate still enters the river system every day, and it will be years before it is fully flushed out.
No one is saying a few glasses of tap water pose an immediate danger.
Environmental health scientists say there is an outside risk of developing health problems from perchlorate, basing their estimates on the assumption that a person would drink about two liters of the slightly tainted water each day of a lifetime.
Nonetheless, environmental groups say perchlorate's presence in the Colorado River raises questions about the safety of drinking the river's water and of eating foods, such as lettuce, that are grown with it.
Questions are thought to be particularly significant for pregnant women and babies. Perchlorate is known to affect the production of thyroid hormones, which are considered critical to brain development, so fetuses and newborn children may face a greater risk.
"The more we know about perchlorate, the more concerned we get, because the science is pointing to low doses affecting brain functions," said Gina Solomon, a health expert with the Natural Council, an environmental group.
"The kind of things that low to moderate doses of perchlorate might do include delays in things like language acquisition, motor coordination," Solomon said.
In all, more than 15 million people, including those in the urban expanses of Las Vegas and much of Southern California, depend on drinking water from the lower Colorado River. Roughly 15% of California's water supply comes from the river.
Water siphoned off to the casinos of Las Vegas contains 10 to 12 parts per billion of perchlorate, according to officials with the Southern Nevada Water Authority. Water diverted
downstream by the Metropolitan Water District of Southern California is less polluted, usually somewhere between 5 and 8 parts per billion. It is subsequently blended with Northern
California water before being piped to Southern California