A chemical compound in plastic products may be hazardous to human health. A growing body of scientific evidence suggests that the chemical, known as Bisphenol A, is linked to an increased risk for metabolic disorders, cellular abnormalities and heart disease.

Bisphenol A (BPA) is used as a building block for the production of polycarbonate plastics found in a variety of household consumer products, including baby bottles, some food storage containers, and the linings of milk containers and food cans. The chemical is also present in some water pipes and dental sealants.

Although plastics may appear to be sturdy, scientists have known for many years that the chemical linkage between individual BPA molecules is unstable. This chemical instability is what allows BPA to leach into food and beverages that come in contact with the plastics.

About 2 billion pounds of BPA are produced annually in the United States, and human exposure to the substance is widespread. Scientists estimate that over 90 percent of Americans have measurable blood levels of the chemical compound.

Researchers at the University of Cincinnati recently reported that BPA is a risk factor for metabolic syndrome, a condition characterized by high blood pressure, cholesterol and blood sugar abnormalities, and excess abdominal fat. Approximately one in four Americans currently suffers from metabolic syndrome, according to the National Institutes of Health.

In laboratory studies, the University of Cincinnati scientists exposed freshly collected human fat tissue to BPA. The results of their research revealed that BPA suppresses adiponectin, a hormone that plays a key role in the regulation of insulin and blood sugar in the body.

Higher urine levels of BPA are associated with heart disease, type 2 diabetes and liver-enzyme abnormalities, according to the results of a study published in the Sept. 17 issue of Journal of the American Medical Association (JAMA). The release of the study coincides with a Food and Drug Administration hearing concerning the health risks of BPA.

Earlier this month, a report released by the National Toxicology Program indicated that the current level of exposure to BPA is a cause of concern regarding effects on developing brain and prostate tissues in unborn babies, infants and children. High concentrations of the chemical have been reported in the blood of some pregnant women in the United States.

Recent research reveals that BPA can alter the development of the reproductive tract of unborn females. Some experts fear that the chemical may negatively impact the future fertility of individuals who were exposed to the chemical even before birth.

In 2005, Yale researchers determined that low doses of BPA can impair brain function, leading to learning disabilities and age-related degenerative brain diseases. The results of a study performed by University of Cincinnati researchers demonstrated that BPA exerts negative effects on brain tissue, even when present in minute quantities.

BPA is a weak synthetic estrogen that mimics the actions of natural estrogens in the body. Although natural estrogen has many positive effects, it is known to trigger cancer of the breast and uterus in some individuals.

In April 2008, researchers at the California Pacific Medical Center Research Institute reported that exposure to BPA causes normal, non-cancerous human breast cells to express genes that are characteristic of aggressive breast cancer cells. Previous research suggested that BPA exposure may increase the growth of some prostate cancer cells, as well.

If you're concerned about the health risks associated with BPA, there are a few steps you can take to reduce your exposure, including avoiding microwaving food or beverages in polycarbonate plastic containers. Polycarbonate containers with BPA are usually stamped with "No. 7" on the bottom.

It's also a good idea to opt for containers made of glass, porcelain or stainless steel whenever possible, especially when preparing or serving hot foods or liquids. Only BPA-free baby bottles should be used to feed infants.

While the age and condition of plastic products is commonly believed to be a factor in BPA exposure, a University of Cincinnati study recently revealed that old polycarbonate plastic bottles release the same amount of BPA as new bottles. When exposed to boiling water, both old and new bottles released BPA as much as 55 times more rapidly than before they were exposed to the hot water.

Although much remains to be learned about the effects of BPA, it is becoming increasingly evident that even at very low levels, long-term exposure to this chemical may be hazardous to your health.

Rallie McAllister is a board-certified family physician, speaker and the author of several books, including "Healthy Lunchbox: The Working Mom's Guide to Keeping You and Your Kids Trim." Her website is www.rallieonhealth.com. To find out more about Rallie McAllister, M.D., and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate Web page at www.creators.com.

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