A study by the Centers for Disease Control and Prevention in Atlanta estimated that the brands that contain only the minimum iodine concentration of 5 micrograms would leave infants iodine-deficient, and thus more vulnerable to the toxic effects of perchlorate.
When perchlorate enters the body it can block the thyroid gland from taking up iodine.
The study, published in the Journal of Exposure Science and Environmental Epidemiology, found that perchlorate exposure may be higher in infants compared with older persons, due to diet -- infant formula -- and body weight versus intake considerations.
Bovine milk-based powdered infant formulas with lactose had a significantly higher perchlorate concentration than soy, lactose-free and elemental powdered infant formulas, the study said.
"Perchlorate contamination of drinking water is a very serious concern, particularly for infants," Dr. Anila Jacob, a senior scientist with Environmental Working Group, said in a statement. "As this unprecedented study demonstrates, infants fed cow's milk-based powdered formula could be exposed to perchlorate from two sources -- tap water and formula."