Additional source of dietary 'estrogens.' (many canned foods contain bisphenol-A, a contaminant that mimics estrogen)(Brief Article)

Many canned foods on supermarket shelves contain small quantities of an estrogenlike pollutant, a new study reports. This hormone-mimicking

contaminant--bisphenol-A (BPA)--appears to leach from the plastic resins coating the inside of affected cans.

Exposure to estrogen mimics has become a source of growing concern since recent studies began linking these ubiquitous contaminants with increased risks of breast cancer (SN: 7/3/93, p.10) and reproductive abnormalities (SN: 1/22/94, p.56). During the past 4 years, endocrinologists have identified two types of plastics that can shed estrogenlike constituents.

Realizing that many food processors coat cans to avoid flavor-altering chemical reactions between the cans and their contents, Nicolas Olea and his coworkers at the University of Granada in Spain analyzed 20 different brands of canned goods. Purchased locally and in the United States, these included corn, artichoke hearts, mushrooms, tomatoes, and peas.

BPA turned up in roughly half of the items, the researchers report in the June Environmental Health Perspectives. Food processors note that about 40 percent of food cans in Spain are lined with plastic, compared to 85 percent in the United States.

Two years ago, David Feldman and Aruna V. Krishnan of Stanford University School of Medicine reported that BPA can leach from plastic subjected to high temperatures, such as those that occur during the autoclaving of laboratory equipment (SN: 7/3/93, p.10). Olea told Science News that the sterilization of canned foods closely resembles that process.

Once plastic has been heated, BPA can continue to leach out. For instance, when a plastic-lined can was washed out and refilled with water, that water soon picked up measurable quantities of BPA, Olea's team reports. The pH of the food did not appear to affect leaching.

Where present, BPA occurred in trace quantities--just 4 to 22 micrograms per 300 grams of food. That's well below the 3 milligrams per kilogram of BPA allowed under regulations set by the European Union. BPA is also FDA-approved, and "no research or experience has suggested it might cause any adverse effects," says Roger Coleman of the National Food Processors Association in Washington, D.C.

Feldman's studies indicate that BPA possesses only one-thousandth the potency of estradiol, the major estrogen in humans. However, the body breaks down estradiol quickly, notes endocrinologist Ana M. Soto of Tufts University School of Medicine in Boston. If BPA lasts longer than estradiol or if the body cannot inactivate BPA as efficiently, "then it might prove more active than it at first sight appeared," she says.