The report was published Feb. 22 on the Web site of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
Perchlorate occurs naturally and is also a primary ingredient in solid rocket fuel. The chemical, which has been showing up in many segments of the environment, can interfere with iodide uptake in the thyroid gland, disrupting adult metabolism and childhood development.
The researchers, led by Professor Purnendu Dasgupta, Ph.D., of the university's department of chemistry and biochemistry, analyzed 47 dairy milk samples purchased randomly from grocery stores in 11 states, and 36 breast milk samples from women recruited at random in 18 states. Every sample of breast milk contained perchlorate, and only one sample of dairy milk contained no detectable levels.
The average perchlorate concentration in breast milk was 10.5 micrograms per liter; the dairy milk average was 2.0 micrograms per liter. No definitive national standard exists, although the U.S. Environmental Protection Agency had suggested a limit of 1.0 micrograms per liter in drinking water.
The researchers also found that high levels of perchlorate correlated with low levels of iodide in breast milk, which can inhibit thyroid function in nursing womenan essential component for proper neural development of the fetus. Although the data are limited, the levels of iodide in this study are sufficiently low to be of concern, according to the researchers. They suggest that the recommended daily intake of iodine for pregnant and nursing women may need to be revised upwards.