Pregnant women who eat canned vegetables daily have elevated levels of bisphenol A, an estrogenic chemical found in food containers and other consumer products, according to new research published today.

More than 90 percent of pregnant women have detectable levels of bisphenol A, according to the study, and a variety of sources of the chemical were identified. Pregnant women who were exposed to tobacco smoke or worked as cashiers also had above-average concentrations in their bodies.

Bisphenol A, or BPA, is an estrogen-mimicking chemical used in food and beverage can linings, polycarbonate plastic and cash register receipts. Lab animals exposed in the womb to low amounts of BPA develop prostate and mammary gland cancers, obesity and reproductive problems. In humans, BPA has been linked to heart disease and diabetes.

A few years ago, many mothers reacted strongly to protect their infants from BPA by pressuring retailers and manufacturers to offer BPA-free baby bottles. But the new study shows that pregnant women are still unwittingly exposing their infants during fetal development, which is an even more vulnerable time.

This really highlights that there are a lot of sources of BPA exposure during pregnancy,” said Joe Braun, a research fellow at the Harvard School of Public Health and lead author of the study conducted by scientists from seven institutions. “This identifies some sources that are modifiable, meaning that women can actually lower their exposures to them.”

The researchers tested the urine of 386 pregnant women in the Cincinnati area who delivered babies between 2003 and 2006. One woman was excluded because her BPA levels were extraordinarily high – 1,000 times higher than the group’s median.

At 16 and 26 weeks into their pregnancy, more than 90 percent of the women had BPA in their urine, while 87 percent had detectable levels when their babies were born.

One of the strongest links was to canned vegetables.

Those who consumed canned vegetables at least once a day had 44 percent more BPA in their urine than those who consumed no canned vegetables, according to the study, which was published in the scientific journal Environmental Health Perspectives.

BPA concentrations did not vary with consumption of canned fruit, fresh fruits and vegetables, or fresh and frozen fish.

Tracey Woodruff, director of University of California, San Francisco’s Program on Reproductive Health and the Environment, emphasized that vegetables and fruit are an important part of nutrition for pregnant women. But she said the new report suggests that it would be best to choose fresh produce instead of canned.

Women with lower education had higher BPA concentrations, and the researchers speculated that it may be related to consumption of more canned vegetables. A weaker link was found to income, with slightly higher BPA levels found in women earning less than $20,000 annually.

Women who said they were partial vegetarians had higher BPA levels than women who were strict vegetarians or non-vegetarians. The authors couldn’t explain that finding, saying their data was limited because only five of the women were strict vegetarians. Choice of organic produce made no difference in BPA levels.

Experts have long suspected that most exposure to BPA comes from eating foods or beverages contaminated with the chemical when it seeps from cans and hard plastic bottles. But the new data provide a glimpse at the importance of other sources, too.

The women’s occupation mattered: Women who were cashiers had the highest concentrations, while industrial workers and teachers had the lowest. The pregnant cashiers had on average 55 percent more BPA in their urine than the pregnant teachers.

BPA is found in some cash register receipts, and it could be absorbed through the skin or ingested. Wearing gloves may reduce exposure. Some companies are eliminating the chemical. Appleton Papers, the largest producer of thermal papers in North America, said that it stopped using BPA in 2006.

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