Bisphenol-A, or BPA—a common, human-made chemical that enters most of our bodies everyday—has been linked to heart disease, a new study says.
BPA is commonly used in consumer plastics, particularly polycarbonate plastic items such as many sunglasses, reusable bottles, food packaging, and baby bottles. It also lines the inside of food cans.
In a sampling of U.S. adults, those with the highest levels of BPA in their urine were more than twice as likely to suffer from coronary heart disease than those with the lowest concentrations of BPA.
The findings almost perfectly dovetail with a 2008 study on the same topic, said study co-author Tamara Galloway, an ecotoxicologist at the U.K.'s University of Exeter.
"If you see it once, that's interesting," Galloway said.
"If you see it twice in a separate population, it's a strong indication that what you're seeing is not just some chance finding."
Frederick vom Saal, a BPA researcher at the University of Missouri-Columbia, agreed that the two sets of "data are compelling and demonstrate repeatability"—the point at which scientific findings move from preliminary to validated.
Study co-author Galloway cautioned, however, that no direct cause-and-effect had been found between BPA and heart disease. It remains possible that the two may be only indirectly linked.
BPA Mimics Estrogen
The American Chemistry Council, which represents the U.S. plastic industry, says that "minimal" exposure to BPA poses no known risk to human health.
Still, BPA's ability to mimic estrogen—and spur reproductive mutations in the womb—has been well documented, leading some cities in the U.S., Canada, and Europe to ban BPA-containing products.
Meanwhile, BPA's "effects in adults have largely been overlooked," Galloway said, despite the fact that the chemical is found in more than 90 percent of the U.S. population.
So Galloway and colleagues examined data from the U.S. National Health and Nutrition Examination Survey, the only large-scale data set of adult health and nutrition in the world.
The team examined BPA concentrations in the urine samples of 1,493 adults taken between 2005 and 2006. A quarter of the people had "higher amounts" of BPA, the study says.
"Expand that to six billion"—roughly the world's current population—"and you've got a billion people in harm's way," said the University of Missouri's vom Saal, who was not involved in the new study.
BPA Exposure Decreasing?
The previous study, which had used data from 1,455 U.S. adults tested between 2003 and 2004, found an association between higher rates of BPA and occurrences of heart disease, diabetes, and abnormal liver enzymes.
The new study revealed the same relationship, though the diabetes and liver-enzyme links were not statistically meaningful, the researchers say.
There was one big difference between the two data sets that surprised study co-author Galloway: The average level of BPA exposure in the 2005-2006 group was a third lower than the level in the earlier group.
The drop in BPA levels may be because more people are steering clear of obvious exposures to the chemical, and because some industries—such as plastic-bottle manufacturers—have voluntarily cut out BPA, experts speculate.
One unknown that requires "urgent" attention is how exactly the chemical might encourage heart disease in the body, according to the study published tomorrow in the journal PLoS One.
Cutting BPA Risks a No-Brainer
Bisphenol-A exposure is certainly not the only factor in heart disease, but reducing at least one possible risk is a "no brainer," the University of Missouri's vom Saal said.
For instance, people can limit their exposure by not microwaving polycarbonate plastic food containers (which normally have number sevens on their undersides), avoiding canned foods, and using BPA-free baby bottles, according to the U.S. National Institute of Environmental Health Sciences.
"It's not a pretty picture," vom Saal added.
"This is a bad chemical, and it should not be used in the way it's being used."