Probing Question: Is plastic dangerous?

milk bottle with baby in background

Sipping water from a bottle after a workout, microwaving a container of leftovers for lunch, giving the baby a bottle of milk: We use plastic every day, without even thinking about it. But numerous reports have suggested that exposure to bisphenol-A, an organic compound present in many food and beverage containers, could actually be damaging to our health. Is plastic dangerous?

Based on the type of polymer used, plastics can be divided into seven different groups ranging from the low density polyethylenes used for zip-lock bags to the polystyrenes used for egg cartons. Bisphenol-A, or BPA, is found in polycarbonate plastics—the hard, clear plastics often used for food and beverage containers, in baby bottles, and even as a lining for canned foods.

Trace amounts of BPA can leach from the plastic into the food, and from there into our bodies, says Jeffrey Peters, Penn State professor of molecular toxicology. This is worrisome, he explains, because scientific studies have shown that lab rats fed or injected with BPA were more likely to have health problems. Another study, published in the Journal of the American Medical Association, showed that humans with high BPA levels in their urine were more likely to be obese or diabetic. Should we ditch the plasticware?

"BPA is definitely a concern," says Peters, "but, as of right now, the data are not complete enough to establish a cause and effect between the use of these plastics and the onset of disease," he cautions. The problem, he explains, is that not enough studies have been done in humans. "We don't really know how BPA works to cause these health problems. BPA is known to mimic the hormone estrogen, but the exact mechanism is not known."

Although taking a somewhat skeptical view of the BPA controversy, Peters concedes that the groups most at risk for any potential health risks are babies and young children, who would be exposed to BPA by using plastic baby bottles and consuming canned formula. A report from the National Institutes of Health National Toxicology Program investigated the potential human reproductive and developmental risks posed by exposure to BPA and concluded that it has "some concern for effects on the brain, behavior, and prostate gland in fetuses, infants, and children at current human exposures to bisphenol-A."

Peters notes that at the level of BPA which most people are exposed to, researchers believe there is only "limited evidence of adverse effects" to the health of adults, but for babies and young children, this is elevated to "some concern for adverse risks."

This difference in risk, explains Peters, is based on a couple of factors. The first is that in proportion to their small body size, babies and young children consume more food and liquid than adults, and so can also take in a higher amount of BPA. The second factor is that the delicate systems of babies and young children are not able to metabolize BPA as efficiently as adults.

The jury is still out on the level of threat posed by BPA, but the fact remains that many people are exposed to it every day, and the way we use our plasticware may exacerbate the problem. High temperatures increase BPA leaching, which means that microwaving a plastic container of leftovers, or washing a plastic container in hot water, would actually increase the amount of BPA released. Also, the plastic coatings that line cans used for foods and beverages can break down over time, leaching BPA into the can's contents, particularly if the contents have a high acid content (e.g., canned tomatoes).

So what can we do?

Avoiding polycarbonate plastics as much as possible would help to reduce exposure to BPA. There is a plastic identification code stamped onto the bottom of most containers, making it possible to identify the different types of plastic. Polycarbonates fall into the number 7 group, represented by a triangle with the number 7 inside it, sometimes accompanied by the letters "PC." Some other, non-polycarbonate plastics are also categorized into the number 7 group, meaning that not all number 7 plastics will contain BPA; however, this is a good rule of thumb. As alternatives, many retailers now offer BPA-free plastic water containers and baby bottles. Some experts also suggest avoiding canned foods, especially those that have been on the shelf for a long time.

"It's important to remember that there are many potentially dangerous chemicals in our environment which we come into contact with everyday," notes Peters. "We cannot completely eliminate the risks."

Jeffrey Peters, Ph.D., professor of environmental toxicology in the College of Agricultural Sciences, can be reached at

Last Updated January 12, 2009