Feb. 24, 2005 - A toxic chemical found in rocket fuel is present in both cow's milk and human breast milk at levels that could cause harm, research shows.
Investigators found high levels of the chemical perchlorate in 46 of 47 store-bought milk samples from 11 states. And 36 samples of human breast milk tested from a randomly selected group of women living in 18 states contained even higher levels.
The findings suggest that the chemical may be more widespread than has been believed, researchers say. Perchlorate has been found in drinking water from 35 states and occurs naturally at very low levels in the environment.
"We have known that perchlorate is present in cow's milk, but this is the first study to look at breast milk," Texas Tech University researcher Sandy K. Dasgupta, PhD, tells WebMD.
In the Texas Tech University study, the average perchlorate concentration in breast milk was approximately 10 micrograms per liter. That was roughly five times higher than the average amount found in cow's milk (2.0 micrograms per liter).
No national standards exist on safe perchlorate levels, but the Environmental Protection Agency (EPA) has suggested a limit of 0.7 micrograms per kilogram of body weight per day.
If, for example, a 9-pound baby drinks 24 ounces (0.7 liters) of milk containing perchlorate amounts found in the study, it will drink more than twice the suggested limit.
Perchlorate can interfere with the production of thyroid hormones by preventing the thyroid gland from absorbing iodine, an essential component of these hormones. In a pregnant woman, this can lead to developmental problems in the fetus.
It is not yet clear, however, whether perchlorate poses a significant risk to human health at current exposure levels.
In a controversial report issued last month, a panel of experts advising the National Research Council concluded that perchlorate is safe for human consumption at much higher levelsperchlorate is safe for human consumption at much higher levels than had been believed.
The panel set safe exposures at 20 times the levels that had been suggested by the EPA.
Environmental groups and some members of Congress have objected to the panel findings. Critics claim that the panel had been influenced by the Bush administration in an effort to get the environmental polluters off the hook for cleaning up water supplies contaminated with perchlorate.
Panel chairman Richard B. Johnston Jr., MD, tells WebMD the group is examining the data on perchlorate levels in milk and will soon issue a statement on the implications for infants.
Dasgupta tells WebMD that the set amount may be safe for some breastfeeding infants and unsafe for others, depending on how much iodine the mother gets in her diet.
It is of concern, he says, since dietary iodine levels seem to be going down in the United States. In a recent study involving pregnant women living in Boston, almost half had low iodine levels and one in 10 were considered iodine deficient.
Fortified table salt is a major source of dietary iodine, but Dasgupta is quick to point out that eating more salt is a bad idea for pregnant and lactating women. Instead, he recommends that women concerned about perchlorate take iodine supplements made from dried seaweed, which are available at health food stores.
Most tablets contain about 300 or 400 micrograms of iodine -- well below the level generally considered to be safe for daily consumption, he says.