Originally Published: 8/22/2007
By The Issue Wonk
“Polycarbonate plastic is a lightweight, high-performance plastic that possesses a unique balance of toughness, dimensional stability, optical clarity, high heat resistance and excellent electrical resistance.”1 As a result, it is an ideal material for use in a “wide variety of applications,” including a number of home and kitchen applications involving direct contact with food and beverages. Common examples include water bottles, baby bottles, tableware such as plates and cups, and containers for storing food and reheating in a microwave oven.”1
The key building block of polycarbonate plastics if bisphenol A (BPA), a potent hormone disruptor. BPA “may impair the reproductive organs and have adverse effects on tumors, breast tissue development, and prostate development by reducing sperm count.”2 Bisphenol A, a website publication, states that BPA has been studied extensively because of its potential to migrate into foods and beverages. It says:1
These studies consistently show that the potential migration of BPA into food is extremely low, generally less than 5 parts per billion, under conditions typical for uses of polycarbonate products.
Using these results, the estimated dietary intake of BPA from polycarbonate is less than 0.0000125 milligrams per kilogram body weight per day. This level is more than 4000 times lower than the maximum acceptable or “reference” dose for BPA of 0.05 milligrams per kilogram body weight per day established by the U.S. Environmental Protection Agency.
So, we have nothing to worry about? Maybe we do. vom Saal and Hughes3 analyzed the research literature on BPA and found a correlation between the source of funding for the research and the conclusions drawn. They found that industry-funded studies tended to find no significant effects, while government-funded studies tended to find significant effects. They noted that, “In 31 publications with vertebrate and invertebrate animals, significant effects occurred below the predicted ‘safe’ or reference dose of 50 µg/kg/day BPA.”4
Soto5 also published research which described the exposure of pregnant rats to BPA at 2.5 to 1,000 µg per kg of body weight per day. At the equivalent of puberty for pups (50 days old), about 25% of their mammary ducts had precancerous lesions, some three to four times higher than unexposed controls. This study is cited as evidence for the hypothesis that environmental exposure to BPA as a fetus can cause breast cancer in adult women.
BPA can leach into food and beverages through normal use and exposure to heat and cleaning agents. “This includes leaving your plastic water bottle in your car during errands, in your back pack during hikes and running it through your dishwasher and using harsh detergents.”2 In fact, “a 2003 study conducted by the University of Missouri published in the journal Environmental Health Perspectives . . . also found that detectable levels of BPA leached into liquids at room temperature.”2 EcoMall noted, “Baby bottles made from polycarbonate plastics have quietly disappeared from the market despite industry assurances the polycarbonate plastics are safe.”
A consensus statement from 38 scientists recently released in Reproductive Toxicology concludes that low BPA exposures in the womb may cause increases in the rates of prostate and breast cancer, reproductive abnormalities, lowered sperm counts, early onset of puberty, and obesity and insulin-resistant diabetes.6 Another recent paper concluded that BPA levels in human tissues are higher than levels sufficient to cause adverse affects in lab animals. “The analysis reports that many people are exposed to more than 50 µg per kg of body weight per day, the safety threshold set by EPA in 1984.6
Another interesting research finding was that exposure to BPA in the womb altered the coat colors of genetically identical agouti mice. “By preventing methylation of DNA, which normally silences genes, BPA causes a change in the fur color of the mice from the normal brown to yellow. Yellow agouti mice always become obese and develop diabetes as adults.”6
It should be noted that Steven Hentges, the executive director of the polycarbonate/BPA group at the American Chemistry Council, an industry group, disputes all this new research. He says it isn’t credible.6
1 Polycarbonate Plastics and Bisphenol A Release. Bisphenol A.
2 Are Plastic Water Bottles Safe? EcoMall.
3 vom Saal, Frederick S. & Hughes, Claude. (2005) An Extensive New Literature Concerning Low-Dose Effects of Bisphenol A Shows the Need for a New Risk Assessment. Environmental Health Perspectives, 113(8).
4 µg is scientific notation that refers to a microgram, which is 1/1,000,000 of a gram.
5 Hileman, Bette. Bisphenol A May Trigger Human Breast Cancer. Chemical & Engineering News, December 6, 2006.
6 Hileman, Bette. More Concerns Over Bisphenol A. Chemical & Engineering News, August 6, 2007.
© The Issue Wonk, 2007