Packaging is pegged as the most likely source.

By Janet Raloff

Web edition: November 2, 2010

Some communities have banned the sale of plastic baby bottles and sippy cups manufactured using bisphenol A, a hormone-mimicking chemical. In a few grocery stores, cashiers have already begun donning gloves to avoid handling thermal receipt paper out of fear its BPA-based surface coating may rub off on the fingers. But how’s a family to avoid exposure to this contaminant when it taints the food supply?

It’s a question many people may start asking in response to data posted online November 1 in Environmental Science & Technology by a team of university and government scientists. Indeed, the last author on the paper is Linda Birnbaum, director of the National Institute of Environmental Health Sciences.

In recent years, she's teamed up with toxicologist Arnold Schecter of the University of Texas School of Public Health on market-basket analyses of foods for various potentially toxic pollutants. Like Birnbaum, Schecter initially gained renown for studying dioxins. Now, both have moved into the BPA arena.

In their team’s new paper, the Texas contingent locally purchased three samples of each of 31 types of canned or plastic-packaged foods. Another four examples of fresh meat and eight different types of pet food were also collected. All were analyzed for BPA — and 60 percent of the different food products hosted measurable quantities. Ironically, pet food contained less of the pollutant than did most of the items destined for human consumption.

Kudos to the team for doing the unusual: Naming names. As I noted in my recent blog on red-yeast-rice supplements, researchers all too often fail to identify products by name. So if one is off-the-charts-high — or low — with regard to some contaminant of concern, we don’t get a chance to alter our purchasing habits. Not so here. Schecter’s group publishes the brands and full name of the products it sampled — right next to the values of BPA measured in each.

Although there was some variation in BPA levels among samples of a given product, it wasn’t very big. The Dallas grocery offerings sometimes fell well below certain foods — different foods — purchased overseas as part of earlier studies by others. Which means there can be wide variation in food contamination.

Schecter’s team did find that in some instances, one brand of a food — like canned tuna or chicken soup — contained measurable amounts of BPA, and another had none.

Such data “affirm our hypothesis that food packaging systematically causes the occurrence of BPA in food,” they conclude. A likely source is the protective BPA-laced resin that many manufacturers use to line their cans (to keep foods from leaching some of the metal). However, the fact that some canned goods had substantial BPA values and others nil suggests that manufacturers are able to can foods without relying on a BPA-based coating. Which then raises the question: Why don’t more do it?

The authors attempted to calculate likely BPA ingestion rates if some of the more highly contaminated foods were dietary staples for families. And they note that eating several of these foods on the same day wouldn’t bring intake values — even among children — anywhere near the upper limit of 50 micrograms per kilogram body weight recommended by the U.S. Environmental Protection Agency and European Food Safety Authority.

That said, Schecter’s group pointed out that the European Commission’s Scientific Committee on Food Safety has proposed a 10 µg/kg bodyweight daily limit for BPA in food. And that quantity could be reached by downing some of the more heavily contaminated foods identified in this survey.

So what were those foods?

Topping the list: Del Monte Fresh Cut Green Beans sporting 26.6 to 65 nanograms of BPA per gram of product; Progresso Light Homestyle Vegetable and Rice Soup with 15.6 to 22.7 ng/g; two more Progresso soups with 4.46 to 11.7 ng/g; Campbell’s Condensed Chicken Noodle Soup with 4.46 to 7.05 ng/g; and Chef Boyardee Spaghetti and Meatballs with 4.31 to 5.04 ng/g.

Among items at the bottom, containing less than the 0.2 ng/g limit of detection: fresh ham, sliced chicken breast, fresh salmon, five of the pet food offerings, Hormel’s spam, Campbell’s Chicken Noodle Soup 2.5%; Similac Advanced Infant Formula, Chef Boyardee Mac and Cheese, Bumble Bee Chunk Light Tuna in Water and Hunt’s 100% Natural Tomato Paste.

Clearly, Schecter’s group writes: “The levels of BPA found in this study did not reach concentrations which to date have been associated with adverse health effects.” But foods are hardly the only source of BPA. In fact, chemists working on thermal papers believe store receipts could, for many people, be a substantially larger source of exposure.

As such, Schecter and Birnbaum's group concludes, “it is important to continue monitoring the U.S. food and water supply for BPA, and investigating other potential pathways of exposure.” Like store receipts.

See also: Skin is no barrier to BPA, study shows