Adding iodide to prenatal vitamin supplements appears to be more effective at protecting public health from iodine deficiency than ratcheting down the amount of perchlorate in drinking water, says a report by EPA's Office of Inspector General (OIG). Perchlorate, which can occur naturally, is a component of rocket fuel and contaminates many water supplies. This compound inhibits uptake of iodine by the thyroid. Low iodine levels decrease the amount of thyroid hormone in pregnant and nursing women and can impair brain development of their fetuses and infants. OIG assessed the health risks from exposure to perchlorate combined with three other factors—exposure to thiocyanate and nitrate and lack of iodine in the diet—that lead to lowered uptake of iodine. OIG concluded that lowering the amount of perchlorate allowed in drinking water from the current limit of 24.5 ppb "provides a negligible decrease" in the number of babies at risk for impaired brain development. But getting women to take prenatal vitamins containing iodide has the potential to protect, at a relatively low cost, babies born to mothers who are deficient in iodine, OIG said.