Patricia Hunt, Ph.D., lead author of the study appearing in the April issue of the journal Current Biology, is concerned because the compound, called Bisphenol A (BPA), which shows hormone-like properties and mimics the effects of naturally produced estrogens, produces a significant increase in genetic abnormalities at extremely low levels.
“Our studies provide the first direct evidence that environmental exposure to BPA acts to disrupt the maturation of the egg and demonstrate a dose-related increase in abnormalities,” says Hunt, an associate professor of genetics at the Case Western Reserve University School of Medicine and an expert in the causes of genetic abnormalities in egg cells. “In addition, they show that, at least in the mouse, exposure to very low doses of BPA within the human exposure range produces detectable effects.”
“These studies raise important questions about the potential impact on human reproduction of BPA and other man-made substances that mimic the actions of hormones,” she says.
Hunt’s laboratory began studying the effects of BPA after control (or normal) mice in research projects began showing genetic abnormalities. In mice, the rate of these abnormalities usually is low. The defects were traced to plastic cages and plastic water bottles that had been inadvertently cleaned with a harsh detergent. The detergent caused BPA to leach from the polycarbonate material used to make the cages and bottles. Over several years, Hunt and her team proceeded to determine how much BPA the mice had been inadvertently exposed to, which was a relatively large amount. Then, they scaled back to see how small a dose would produce effects. This amounted to daily doses of 20 parts/billion over five to seven days, an extremely low level. “We can’t say anything about the effects of BPA on humans,” says Hunt. “Nevertheless, the cell division program for eggs is extraordinarily similar in mice and humans, and the results of our studies in mice are disturbing because brief exposure during the final stages of egg growth were sufficient to cause significant increases in meiotic abnormalities.”
Other authors on the study from Case Western Reserve University are K.E. Koehler, C.A. Hodges, A. Ilagan, R.C. Voigt, T. J. Hassold; from Thoren Caging Systems, Inc., S. Thomas, and from RTI International Research Triangle, B.F. Thomas.
Current Biology