Plastics and the BPA Story

Bisphenol A is a material used in hard, lightweight plastics called polycarbonates. Some baby bottles and water bottles are made from bisphenol A. Enormous amounts of BPA are produced each year -- about 6 billion pounds.

Although bisphenol A came to fame on the nightly news as a potential poison in our water bottles, our main exposure comes from the linings of canned foods, according to Vandenberg, who studies BPA.

"Over a dozen studies clearly show that BPA is not only leaching from cans, but it reaches the food stored inside," says Vandenberg.

The BPA we ingest gets into our bloodstream. Regular monitoring by the CDC shows that more than 90% of us have detectable levels of bisphenol A in our bodies.

Among all the other plastic substances that get into our food, BPA stands out, according to Vandenberg, for its ability to disrupt the functions of hormones -- especially estrogen.

Hundreds of studies show that high doses of BPA disrupt reproductive development and function in laboratory animals. Levels in humans were thought to be too low to be of concern, but more recent research has challenged that perception, Vandenberg tells WebMD.

"Several animal studies suggest that BPA has effects at much lower doses than previously believed," says Vandenberg. "The levels of BPA in people frequently exceed the levels shown to have effects in rodents in these studies," she adds.

Chemical industry sources are quick to point out that this "low-dose hypothesis" has not yet been proven. They cite studies that have not shown harm from BPA at low doses in rodents. However, a new study in a prestigious journal also shows the low-dose BPA effect not just in rats but in monkeys, whose systems are more like humans.

One large, well-conducted study in humans showed that people who had high levels of BPA in the urine had a higher rate of diabetes, heart disease, and liver toxicity.

Altogether, Vandenberg believes a "fragile consensus" exists among scientists that BPA might be harmful. "Looking at the data we have, there is no reason to conclude we are all safe from BPA's effects," she tells WebMD.