Perchlorate came into heavy use in the 1940s as a component of rocket fuel. Since then, wastewater from rocket fuel manufacture has soaked into the ground and into the water supply at military production sites around the country. The Kerr-McGee Corporation's facility outside Las Vegas, for example, continues to leach 450 pounds of perchlorate per day into a nearby wash that drains into Lake Mead and the Colorado River, according to Senator Dianne Feinstein.
Last year the EPA issued a non-enforceable risk assessment that perchlorate is dangerous to humans in drinking-water concentrations above one part per billion. The Colorado River, which provides water to 15 million people in the Southwest, typically contains perchlorate at levels between three and ten parts per billion.
Two recent studies have demonstrated that the risks posed by perchlorate in the Colorado River are amplified when its water is used for irrigation. A study by the nonprofit Environmental Working Group (EWG) in Oakland, California, bears out an EPA finding that lettuce absorbs and concentrates perchlorate from contaminated irrigation water. EWG tested 22 samples of lettuce purchased in the San Francisco Bay Area during January and February, when 90 percent of U.S. lettuce comes from the Southwest. Four of the samples contained perchlorate in excess of 30 parts per billion. The highest rate of contamination occurred in “mixed organic baby greens.”
Efforts by environmental groups and California's senators, Barbara Boxer and Dianne Feinstein, to regulate perchlorate have been stymied by the EPA's recent annoucement that it will not expand the drinking-water standard to include toxins such as perchlorate. The EPA's decision delays regulation and clean-up of perchlorate by at least five years. EWG's Bill Walker maintains that this decision is “part of a pattern of the Bush Administration shoving the issue of perchlorate contamination to the back burner.”
If the EPA established the perchlorate level in drinking water below five parts per billion, the Pentagon and contractors who produced and disposed of the chemical would be liable for billions of dollars worth of clean up.