Perchlorate, a tasteless, colorless component of solid rocket fuel, has been detected in the drinking water of 26 states. Despite its toxicity, it is not yet regulated.

However, the Environmental Protection Agency’s Office of Water is considering new drinking water standards for the dangerous salt, following a recent National Academy of Sciences report. The EPA had previously estimated that a safe dose was 1 part per billion. But in February, based on the report’s findings, the agency raised that number to 24.5 parts per billion.

Critics cite two problems with the new number: It ignores perchlorate exposure from food, and it is based on adult bodyweight and water consumption, although children face the greatest risks.

"I thought it was a bit reckless," says Dr. Gina Solomon, senior scientist with the Natural Resources Defense Council.

Perchlorate disrupts iodine intake and thyroid function. In adults, the thyroid gland regulates metabolism, but in developing infants, low levels of thyroid hormone can cause cretinism — a severe form of mental retardation.

During the Cold War, large-scale missile production inundated military sites with perchlorate (HCN, 4/28/03: Perchlorate: it’s not just for rocket fuel anymore). Specific regulations for cleanup efforts do not currently exist, but the study will provide guidelines, says Suzanne Ackerman, an EPA spokesperson.

Dissatisfied with the lack of federal regulation, some states are taking action on their own. California plans to enforce drinking water standards of 6 parts per billion by the end of this year. "None of us should have to drink perchlorate," says Renee Sharp of the Washington, D.C.-based Environmental Working Group. "The stuff is rocket fuel."