Scientists in the United States have found traces of a chemical used to make fireworks and rocket fuel in powdered baby milk.
The team at the U.S. Centers for Disease Control and Prevention (CDC) tested infant formula for traces of the chemical perchlorate, which according to the Environmental Protection Agency (EPA) has been found both drinking water and groundwater in as many as 35 states in the U.S., concern has been raised because the chemical can damage thyroid function.
Perchlorate can inhibit the thyroid gland's iodine uptake, interfering with fetal development - in adults, the thyroid gland helps regulate the metabolism by releasing hormones, while in children, the thyroid helps normal development to take place.
Perchlorates occur both naturally and through manufacturing and are the salts derived from perchloric acid (HClO4). They have been used as a medicine for more than 50 years to treat thyroid gland disorders such as hyperthyroidism.
In 2004, the chemical was found in cow's milk and the suspicion was that it may have entered the cows through feeding on crops that had exposure to water containing perchlorates. In some areas perchlorate is detected because of contamination from industrial sites that use or manufacture it, but in other areas the source of perchlorate is unclear and may occur naturally.
Fireworks are also a source of perchlorate in lakes and the disposal of unused rocket motors and ammunition has led to contamination by perchlorates of several military installations.
The CDC researchers found the highest levels of perchlorate were in baby formulas derived from cow's milk, they also looked at soy-based formulas, as well as formulas from lactose-free cow's milk and synthetic amino acids.
The study does not point out which brands were tested, but says each one contained detectable levels - neither does it deal with the impact traces of perchlorate can have on human health. It is suggested that some factors could offset the chemical, including the presence of iodine and a baby's weight and formula consumption may also influence the risk.
The researchers say the samples were all taken from one city, suggesting that the results might not apply nationwide but critics believe the research provides evidence that the government needs to take a more stringent approach to perchlorate levels.
Cow's milk-based powdered formula could be exposed to perchlorate from two sources - tap water and formula - which suggests that millions of babies are potentially at risk.
The EPA is under pressure from some in the Senate to regulate perchlorate in water but the EPA have held back on new regulations until the National Academy of Sciences studies the matter.
Experts say perchlorate only affects the thyroid gland and is not stored in the body, is not metabolized, and any effects of perchlorate on the thyroid gland are fully reversible once exposure stops.
Some research also suggests that low levels of perchlorate do not pose a threat and may not be as harmful to newborns, pregnant women and other adults as previously thought.
The research is published in the Journal of Exposure Science and Environmental Epidemiology.