Scientists have linked exposure to small levels of a chemical found in public drinking water supplies in 26 states to suppressed thyroid function in more than a third of women and girls 12 and older. The exposure to perchlorate, a study showed, was most acute in women with low levels of iodine in their systems, said Dr. James L. Pirkle, director of sciences in the federal Centers for Disease Control (CDC) and Prevention's Environmental Health laboratory and the study's author. "It's already been known that high levels of exposure to perchlorate [reduce] thyroid function, but this large study of more...