Concern about the potential health effects of bisphenol A (BPA), a chemical widely used in consumer plastic products, is growing, following the release this week of a draft report from the US National Toxicology Program (NTP). That report says there's "some concern" about the potential negative health effects of BPA on infants and children and calls for more research to determine just what the risks of BPA exposure might be.
On Friday, the government of Canada said it would begin a 60-day public comment period on whether to ban baby bottles containing bisphenol A. And water bottle manufacturer Nalgene announced April 18 it would phase out use of BPA in its containers in response to public concern about the chemical.
The NTP report focuses primarily on the possible reproductive and developmental effects of BPA (such as changes in fertility, birth weight, and the development of certain brain regions), not on cancer. However it does note that in some animal studies, BPA has shown effects on breast and prostate tissue, as well as on how early puberty occurs. These effects could be linked to cancer, the report says, but the authors caution that there is not enough evidence to know whether BPA causes cancer -- in animals or in people.
The health effects of BPA are being studied because so many people are exposed to it on a daily basis. The chemical is widely used in plastic water and baby bottles, food packaging, compact discs, and other consumer products; plastics made with BPA usually have the number 7 on the bottom. One survey conducted by the US Centers for Disease Control and Prevention detected BPA in the urine of 93% of people age 6 years and older.
Most Studies in Animals, Not People
The effects on breast and prostate tissue were seen in baby rats. When pregnant rats were injected with BPA, their female pups showed breast tissue changes that some researchers suspected might eventually progress to breast cancer, and male pups showed prostate tissue changes that researchers thought might eventually lead to prostate cancer. Some studies also showed that female mice entered puberty earlier than normal. In humans, early puberty is linked to higher breast cancer risk.
However, the report is careful to explain that these animal results are difficult to apply to humans.
For one thing, the studies did not follow the pups long enough to see whether cancer actually developed. Another problem is that while people are primarily exposed to BPA through their diet, the rats and some of the mice were injected with BPA (some mice got oral doses). The different methods of exposure may affect how the body processes the chemical -- and therefore how BPA affects the body.
The report concludes that there is "some concern" about the adverse health effects of BPA in fetuses, infants and children. "Some concern" is the third level on a scale of 5; "negligible concern" is the lowest level, while "serious concern" is highest.
Even though the evidence isn't conclusive about BPA's link to cancer or other problems, Michael Thun, the American Cancer Society's vice president of Epidemiology and Surveillance Research, says limiting exposure is "prudent."
For those who are concerned about BPA exposure, the US National Institute of Environmental Health Sciences recommends these steps:
- Don't microwave polycarbonate plastic food containers. Polycarbonate is strong and durable, but over time it may break down from over use at high temperatures.
- Polycarbonate containers that contain BPA usually have a #7 on the bottom.
- Reduce your use of canned foods.
- When possible, opt for glass, porcelain or stainless steel containers, particularly for hot food or liquids.
- Use baby bottles that are BPA free.
- Citation: Draft NTP Brief on Bisphenol A [CAS No. 80-05-7]. Published April 14, 2008. Authored by the National Toxicology Program.
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