Their conclusion echoes that of the US Food and Drug Administration (FDA). The FDA issued a draft report last month saying that there is not enough evidence to ban BPA. A public hearing is planned for today to discuss results from their review.

Concern about the chemical, which may be linked possible reproductive and developmental problems, has been growing. In April 2008, Canada became the first country to ban baby bottles containing bisphenol A. And water bottle manufacturer Nalgene decided to phase out use of BPA in its containers in response to public concern.

Further, a new study published in the Journal of the American Medical Association found that U.S. adults with higher urinary concentrations of BPA had a higher prevalence of cardiovascular disease, diabetes, and liver-enzyme abnormalities, indicating the chemical may be linked to adverse health effects even at low doses. More research is needed to confirm the findings, researchers say.

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 actually 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.

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.

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, in animal studies the chemical is often injected. The different methods of exposure may affect how the body processes the chemical -- and therefore how BPA affects the body.

Animal studies suggest that the risk from exposure to BPA may be highest for infants and children. The report concludes that there is "some concern" about the effects of BPA on the brain, behavior, and prostate gland and “minimal concern” about effects on the breast in fetuses, infants and children. "Some concern" is the third level on a scale of 5; "negligible concern" is the lowest level, while "minimal concern" falls in between these two.

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.
• Avoid plastic containers that 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: DNTP Brief on Bisphenol A [CAS No. 80-05-7]. Published September 3, 2008. Authored by the National Toxicology Program.