Perchlorate and iodine: a novel focus on newborns.

For the first time, scientists have compared a woman’s daily intake of iodine and perchlorate with the concentrations of each in her breast milk. They found that a small proportion (about 20%) of iodine enters the breast milk compared with a higher proportion (more than 50%) of perchlorate. Although not definitive, experts say the study, published in ES&T (DOI 10.1021/es801549w), provides further evidence that iodine intake in U.S. mothers is low and that perchlorate could be a problem for newborns. Perchlorate, a major component of rocket fuel, also forms naturally. Health concerns focus on perchlorate’s ability to disrupt thyroid hormone function by competitively blocking the uptake of iodine to the thyroid gland and to breast milk. Iodine is essential to thyroid hormones, which orchestrate brain development in fetuses and young infants. During breast feeding, the thyroid function of infants depends on iodine in maternal milk. Previously published in vitro data suggested that other contaminants, notably thiocyanate, found in cigarette smoke and vegetables like cabbage, and nitrate, found in salad greens, also effectively block iodine from the thyroid and breast milk. But this new study, sponsored by the Gerber Foundation, suggests that for women who do not smoke, perchlorate is the contaminant of concern. In 2005, on the basis of studies of perchlorate dosing in healthy adults, a U.S. National Academy of Sciences (NAS) committee recommended that 0.7 micrograms per kilogram of body weight per day is a safe level. Although the contaminant is found in both food and drinking water, food has emerged as the primary source of low-level exposure for most Americans. Massachusetts and California have set drinking-water standards for perchlorate, but the U.S. EPA is still