The study released Tuesday by the Environmental Working Group comes as state and federal regulators consider setting new standards to regulate perchlorate -- the explosive ingredient in missile fuel that has been linked to thyroid damage.

"Perchlorate exposure is more widespread than we have been led to believe," said Bill Walker, vice president for the West Coast office of the EWG, a research and advocacy organization based in Washington, D.C. The EWG did not call for Californians to stop drinking milk or giving it to their children, but said it does advocate tougher standards for perchlorate.

Perchlorate is a powerful thyroid toxin that can affect the thyroid’s ability to take up the essential nutrient iodide and make thyroid hormones. Small disruptions in thyroid hormone levels during pregnancy can cause lowered IQ and larger disruptions cause mental retardation, loss of hearing and speech, or deficits in motor skills for infants and children...

Neither the EPA nor the state of California have taken into account the numerous common anti-thyroid chemicals which may worsen the effects of perchlorate, notably the drinking water contaminant nitrate. Neither the EPA nor California have taken note of epidemiological studies that found effects on infant thyroid hormone levels at 1 to 6 ppb.

And neither the EPA nor California have adequately considered the extra perchlorate that may be consumed by eating lettuce or other produce grown with contaminated water. Documents obtained and published by EWG in December 2002 showed that a 1997 study in San Bernardino, Calif., of leafy vegetables growing in perchlorate-contaminated water found that the crops took up and stored perchlorate and concentrated it by an average factor of 65. This high rate of bioaccumulation means that a pregnant woman who ate a two-ounce serving of the vegetables would get a dose of perchlorate more than 100 times higher than what the EPA recommends as safe in a liter of drinking water...

Perchlorate is used in fireworks, safety flares, matches and car air bags, but 90 percent of it goes into solid rocket fuel for military missiles and the NASA space shuttle.