| STUDY |
The discovery of a sudden increase in chromosomal abnormalities in a laboratory mouse colony raises anew questions about safe levels of exposure to bisphenol A, a monomer used in polycarbonate plastic and some epoxy resins. The abnormalities in developing mouse eggs occurred at levels of bisphenol A to which people are commonly exposed [Curr. Biol., 13, 546 (2003)]. Similar aberrations in human eggs would lead to miscarriages and birth defects. The research was led by Patricia A. Hunt, an associate professor of genetics at Case Western Reserve University. During experiments in Hunt's lab, a technician accidentally used an alkaline detergent on polycarbonate mouse cages and water bottles. The detergent enabled bisphenol A, a weakly estrogenic substance known as BPA, to leach from the polycarbonate--and suddenly, the mice had many abnormalities in their eggs. When Hunt discovered the chromosomal abnormalities, she deliberately exposed the mice to low doses of BPA, and their eggs developed similar abnormalities. Another study, however, shows that pure water can leach enough bisphenol A from polycarbonate plastic cages to cause human breast cancer cells in petri dishes to proliferate as if they have been exposed to an estrogenic substance [Environ. Health Perspect., published online Feb. 5]. Polycarbonate plastic is used for dental sealants and food and drink containers, including clear plastic baby bottles. Resins made with BPA line most metal food and beverage cans. Scientists interviewed by C&EN consider Hunt's research important for several reasons. The abnormalities in mouse eggs occurred at extremely low levels--about 20 ppb--of BPA exposure. The types of ab-errations induced by BPA would affect offspring of both mice and humans. If a mouse egg with such aberrations were fertilized, it would develop into a nonviable fetus that would be resorbed in the womb, reducing litter size. If BPA caused similar chromosomal aberrations in human eggs, they could be manifested as miscarriages and congenital defects, such as Down's syndrome, Hunt says. BPA levels measured in humans are very close to the exposure levels of the mice in Hunt's work. A German group recently detected BPA levels of 2 to 12 ppb in human maternal and fetal blood. Human and mouse eggs go through almost identical processes of maturation. "Everything we know about how human and mouse eggs are regulated and prepared for fertilization [indicates that these processes are] essentially the same," says John Eppig, senior staff scientist at the Jackson Laboratory, a mammalian genetic research facility in Bar Harbor, Maine. Hunt's work does not prove that BPA causes aberrations in human eggs, but it should make people cautious about how they use polycarbonate plastic, Eppig says. George Pauli, associate director for science and policy in FDA's Office of Food Additive Safety, says the agency is continually evaluating BPA. "We have not had time to review Hunt's research," he says. "We haven't been able to determine what it means in terms of the whole animal." The relevance of Hunt's results to human health has not been established, says Steven G. Hentges, executive director of the American Plastics Council's polycarbonate business unit. He claims that the "potential for BPA to cause reproductive or developmental effects has been" ruled out by two multigeneration rodent studies. |
| UPDATE | 04.03 |
| AUTHOR |
The research was led by Patricia A. Hunt, an associate professor of genetics at Case Western Reserve University. |
| LITERATURE REF. | [Curr. Biol., 13, 546 (2003)]. |
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