C&EN: TODAY'S HEADLINES - OF LETTUCE AND ROCKET FUEL

CHERYL HOGUE

Studies released last week finding perchlorate in lettuce have focused attention on a struggle between EPA and the Pentagon over cleanup standards for the chemical.
Perchlorate—ClO₄^–, a component of solid rocket fuel—disrupts thyroid uptake of iodine and taints water supplies in 20 states.

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A study sponsored by the Press Enterprise of Riverside, Calif., found perchlorate ion in all 18 samples of lettuce analyzed, and a test sponsored by the Environmental Working Group (EWG) detected the substance in four of 22 lettuce samples purchased in California. The source is thought to be irrigation water from the lower Colorado River, which carries perchlorate from a former industrial plant near Las Vegas.

Scientists, regulators, and environmental groups aren’t saying the perchlorate-tainted lettuce poses a public health risk. But the studies demonstrate that much of the population—not just people living near areas polluted with the chemical—may be exposed to perchlorate through vegetables grown using contaminated irrigation water.
The findings highlight a dispute pitting EPA against the military, says Bill Walker, vice president of EWG’s West Coast office. EPA wants a tougher perchlorate cleanup standard, but the Pentagon wants a less stringent one.

In 1999, EPA set a provisional range of 4 to 18 ppb as a “safe” level of perchlorate in drinking water. In 2002, the agency planned to lower that number to 1 ppb but ran into strong resistance from the military. The Pentagon is advocating a 20-ppb standard, which would mean less stringent cleanups of polluted water.

EPA, joined by the military, Energy Department, and NASA, has asked the National Academies to review health impacts of perchlorate.