Most plastic products, even those marketed as BPA-free, leach chemicals that act like the sex hormone estrogen, reveals a new study of 455 common products.

About 70% of the plastic items tested positive for estrogenic activity [EA], but that number jumped to 95% when they were subjected to "real world" conditions such as microwaving and dishwashing, according to the study, published this month in the peer-reviewed journal, Environmental Health Perspectives. Such EA exposure has been shown to alter the structure of human cells, posing potential risks to infants and children.

"Although BPA [bisphenol A] is the most notorious chemical with estrogenic activity used in plastics, it is not the only one, nor does it have the highest biological effect," a study co-author George D. Bittner, a neurobiologist at the University of Texas, Austin, told Chemical & Engineering News.

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"Almost all commercially available plastic products we sampled, independent of the type of resin, product, or retail source, leached chemicals having reliably-detectable EA, including those advertised as BPA-free," the study concludes. "In some cases, BPA-free products released chemicals having more EA than BPA-containing products."

The study doesn't identify specific chemicals but suggests plastics could be reformulated, without great expense, to avoid the problem. It was funded in part by the National Institute of Environmental Health Sciences.

One of the most ubiquitous chemicals, BPA, has become controversial. The U.S. Food and Drug Administration expressed "some concerns" last year about its potential effects on the brain development of fetuses, infants and children but did not say the chemical's unsafe.

Another recent study found that Americans have twice as much BPA in their bodies as Canadians, but it couldn't figure out exactly why.

U.S. cities and states, led by Connecticut and Minnesota are trying to restrict the use of BPA in products aimed at infants and toddlers. The chemical is also widely found in the linings of metal cans and on cash register receipts.