Environmental Toxin Collects in Breast Milk

Zoeller said the study's discovery of how perchlorate is transported to breast milk is important to setting safety standards because perchlorate has a half-life of about eight hours and doesn't accumulate in the body. But because of the new findings, "we no longer have to debate whether perchlorate is being concentrated in milk," he added. "We have enough data to know that this is a very dangerous thing."

Large studies need to be done to confirm the findings, Zoeller added.

It's now "enormously important to find out if perchlorate in [breast] milk is affecting thyroid hormones in infants," he said. Such a study would be difficult to conduct because it would involve drawing blood from 1- and 2-week old infants, Zoeller said.

Tyrone Hayes, a professor of integrative biology at the University of California at Berkeley, said the discovery of a mechanism by which perchlorate can be transmitted to nursing infants is important.

"I think probably the most obvious significance is that we have a very common contaminant in the environment that has a profound negative impact, and that the most profound impact is on humans that don't have a choice at a critical development stage that can impact the rest of their lives," he said.

More information

The Environmental Protection Agency has more on perchlorate.

SOURCES: Nancy Carrasco, M.D., professor, molecular pharmacology, Albert Einstein College of Medicine, Yeshiva University, New York City; Tyrone Hayes, Ph.D., professor, integrative biology, University of California at Berkeley; R. Thomas Zoeller, Ph.D, professor, biology, University of Massachusetts, Amherst; December 3-7, 2007,Proceedings of the National Academy of Sciencesonline