Americans are exposed to far more of a controversial chemical than previously thought — levels that likely surpass the government's current safety standard and which have been shown to cause harm in animals, according to a joint statement issued Thursday by 38 leading scientists.
While the chemical, bisphenol A, is hardly a household word, it is found in nearly every home — and nearly everybody. Government tests have found bisphenol A — used in plastic baby bottles, dental sealants and linings of metal cans — in 95% of people studied.
While scientists haven't yet conducted definitive studies in people, animal tests have linked bisphenol A — which acts like a hormone — to problems such as obesity, early puberty, hyperactivity, and abnormal sexual behavior and reproductive cycles.
In their joint statement, however, scientists say they took a conservative approach, including only statements backed by many strong studies.
Scientists agreed that even very low doses cause profound effects on laboratory animals, particularly during pregnancy and infancy. The chemical can permanently rewire genetic programming before birth, potentially predisposing exposed animals to cancer. Bisphenol A also changes brain structure, body size and behavior in animals studied, scientists said.
Researchers issued their statement, published in Reproductive Toxicology, after reviewing about 700 animal studies.
The Environmental Protection Agency says bisphenol A is safe in doses of up to 50 micrograms per kilogram of body weight, per day. But a paper presented Thursday concludes that the high levels of bisphenol A in human blood and tissue suggest people are actually exposed to 10 times that amount.
One of the scientists, Retha Newbold of the National Institute of Environmental Health Sciences, says researchers need to find ways to measure whether people have been exposed to bisphenol A before or after birth, and if exposure increases their disease risk.
Researchers agree many questions remain, such as: Does bisphenol A, like mercury, build up as it moves through the food chain? Could that explain why there's so much of it in our bodies?
The scientists' findings are at odds with other recent analyses, according to a statement released by the American Chemistry Council, which notes that the European Food Safety Authority has concluded that consumers are not at risk from the chemical. A report on bisphenol A being prepared by the National Toxicology Program's reproductive health center — which will hold a hearing on the issue Monday — will provide a more balanced and accurate picture, said the council's Steven Hentges.
In the past two years, lawmakers in California, Maryland and Minnesota have introduced bills to ban bisphenol A in children's products. None succeeded. California is still considering a bill to ban similar chemicals from children's products.
Frederick vom Saal, a professor of reproductive biology and neurobiology at the University of Missouri-Columbia who signed the joint statement, says manufacturers should voluntarily get rid of bisphenol A. He asks, "Why would you subject your baby to something that you know is a sex hormone?"