The rocket fuel chemical perchlorate has been found in water supplies, in fruits and vegetables, and even in Chile's Atacama Desert. The U.S. Defense Department and military contractors are battling accusations that they have polluted groundwater with the chemical.

The fact that perchlorate occurs naturally can make it difficult to draw conclusions about whether to regulate it or remove it from drinking water supplies. But the fact that perchlorate is more widespread than previously thought suggests to proponents of federal water regulations that there is all the more need to regulate its presence in drinking water.

The debate over perchlorate is moving to the U.S. EPA, which has requested public comments on possible regulation of perchlorate in drinking water. The agency is particularly concerned about the possible impact of perchlorate on the health of very young children. Perchlorate has been known to inhibit the thyroid gland's iodine uptake and interfere with fetal development at high doses.