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.

Elevated levels also were seen in women who smoked cigarettes or breathed secondhand smoke and women exposed to phthalates, chemicals that are found in vinyl products. BPA is used in some cigarette filters and phthalate-containing food packaging.

One strong point of the study is that the scientists tested the women’s blood or urine for compounds, known as biomarkers, left behind by tobacco smoke and phthalates. Those produce more reliable results than the canned food data, which were based on questionnaires.

Information was not collected about the women’s use of plastics, packaged foods, dental treatments or bottled water, all of which may contain BPA.

“There is still very little known about the relative contribution of various sources of BPA to measured urinary BPA concentrations,” the authors wrote. The senior investigator was Bruce Lanphear, formerly of Cincinnati Children’s Hospital Medical Center and now at Simon Fraser University in British Columbia.

For U.S. children, about 99 percent of their BPA comes from food, but no comparable studies have been conducted for adults, Braun said. Additional research is needed, he said, to identify and quantify other sources so that pregnant women can find ways to reduce their fetuses’ exposure.

“If we’re not doing anything about that [fetal exposure], we’re really not doing much to prevent exposure to the most susceptible population,” Braun said.

Woodruff, who did not participate in the study, called upon regulators to control the use of BPA in common items like cash register receipts and aluminum cans. She said the chemical is so ubiquitous it is like air pollution – impossible for people to avoid.

“You can’t avoid it unless you get rid of it,” she said. “Much of this is a failure of the current laws to adequately address non-voluntary chemicals which could harm our health.”

BPA by Occupation

Median BPA in urine (ppm)

Unemployed 1.9
Cashier 2.8
Health Care Worker 2.1
Food Service 2.1
Industrial Worker 1.2
Teacher 1.8
Office Worker 2.1
Sales or service worker    2.1
Other 1.2

Source: “Variability and Predictors of Urinary Bisphenol A Concentrations During Pregnancy,” Environmental Health Perspectives, Oct. 8, 2010

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.