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Government panel will examine safety of plastic chemical
By Tina Hesman Saey
ST. LOUIS POST-DISPATCH
The safety of a chemical that's probably in your cell phone, eyeglass lenses, car, computer, baby bottles, microwaveable dishes — and hundreds of other popular products — will face public scrutiny today.
The chemical bisphenol A is used to make lightweight clear plastics and resins used as adhesives and coatings in everyday products.
Critics are concerned that the chemical could harm human health, particularly the development of fetuses and children, because it works like the female sex hormone estrogen. Other chemicals that mimic estrogen, notably the banned pesticide DDT, have been shown to interfere with hormone function and cause abnormalities in wildlife and laboratory animals.
The chemical industry contends that the weight of scientific evidence on bisphenol A doesn't support the claims of harm. But the chemical has been the subject of much controversy recently. Advertisement
The San Francisco City Council passed a measure to bar bisphenol A and some other components of plastics, from products for children. But the European Union recently increased the level of exposure it considers safe for human health.
Starting today, a panel of 15 scientists convened by the National Institutes of Health's Center for the Evaluation of Risks to Human Reproduction will hold three days of meetings in Alexandria, Va., to examine the safety of bisphenol A. The panel issued a draft report in December but will finalize the report and release its conclusions and recommendations this week. The panel has no regulatory authority, and the findings are not binding.
Frederick S. vom Saal of the University of Missouri-Columbia, one of the leading experts on low-level exposure to bisphenol A, intends to address the scientific panel during a public comment period today. Like everyone else wishing to comment on the draft report, he will get seven minutes to make his remarks. Scientists who study bisphenol A, such as vom Saal, were not invited to participate on the panel.
Bisphenol A was originally developed in the 1930s as an estrogen for birth control, said vom Saal. It was never used for that purpose because scientists quickly discovered that multiple molecules of bisphenol A could link together to form clear, hard plastics, vom Saal said. More than 6 billion pounds of bisphenol A plastics are made globally each year, vom Saal said.
The chemical is ubiquitous and almost unavoidable, vom Saal said. Most people carry the chemical around in their bodies at low levels — about 1 part per billion in blood, urine and tissues.
"That seems like a staggeringly small number until you realize that the natural hormone it's acting like works at levels 10,000 times lower than that," vom Saal said.
Dr. Ana M. Soto, a developmental and cancer biologist at Tufts University in Boston, found while working with breast cancer cells that some components of plastic can act like estrogen. Normally, the breast cancer cells grow only in the presence of estrogen, but she found that some cells were growing even when she didn't add the hormone. The only thing that had changed was composition of the plastic tubes in which she stored components of the media in which the cells were grown; the manufacturer had switched formulas to make the containers more shatter-resistant, Soto said.
She became interested in how bisphenol A might affect developing fetuses. In studies with mice, researchers have found that adult females exposed to bisphenol A in the womb have irregular estrus cycles and stop cycling earlier than unexposed females. The animals exposed to the chemical had changes in a part of the brain that controls ovulation and cycling, Soto said.
Female rats exposed to bisphenol A in the womb developed carcinoma in situ and pre-cancerous changes in their mammary tissue as adults, she said.
But it's not just levels of exposure to the chemical that are important. The fetus takes developmental cues from changing hormone levels. So introducing an estrogen mimic at the wrong time could send the wrong signal to the fetus and throw off development, she said.
"I can't jump and say that bisphenol A causes these effects in humans," Soto said. But scientists cannot ethically test the chemical on human development. People should be concerned about the effect of bisphenol A on human health based upon the animal studies, she said.
The increase in bisphenol A production parallels the rise in obesity, vom Saal said. That's no coincidence, he says. His work with mice suggests that exposure to the chemical during pregnancy can lead to obesity in adulthood.
He also has also linked the chemical to changes in the prostate of male mice whose mothers were exposed to bisphenol A while pregnant.
He points to more than 140 government-sponsored studies that have linked exposure to the chemical to breast cancer, prostate cancer, changes in reproductive organs, brain changes, obesity and other indications of harm. No industry-sponsored studies have uncovered evidence of harm from bisphenol A, vom Saal said.
Industry representatives say looking at individual studies is the wrong approach.
"This isn't a basketball game. You don't just count up studies and see what the score is," said Steven G. Hentges, executive director of the Polycarbonate Bisphenol A Global Group of the American Chemistry Council.
The studies must be considered in aggregate and evaluated for reproducibility, consistency and relevance to human health, Hentges said.
"In every case in which the evidence is evaluated together … , the conclusion is bisphenol A is not a risk to human health, particularly at the low levels to which we are exposed," he said.
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