Bisphenol A exposure increases risk of abnormal heart rhythms

heartbeat irregularitiesThe chemical bisphenol A, commonly found in many plastic household items, has been linked to yet another health problem in animals—an increased frequency of arrhythmias, or , a new study found. The results, seen only in females, will be presented Saturday at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.

Past animal studies show that bisphenol A, or BPA, can have harmful effects on the reproductive, nervous and immune systems. Also, a study in humans reported last year found an increased prevalence of cardiovascular disease in people with high levels of BPA in the urine.

However, the effects of BPA on the heart are unknown, said study co-author Scott Belcher, PhD, associate professor in the University of Cincinnati’s Department of Pharmacology and Cell Biophysics.

In the new study, funded by the National Institutes of Health, the University of Cincinnati researchers found that low-dose BPA and estrogen can act alone or in combination to increase harmful arrhythmias in female rats and mice. Because BPA has properties similar to the main female hormone estrogen, it is considered an “environmental estrogen.”

Mice and rats in the study had normal heart rhythms at baseline, before administration of BPA or estrogen (estradiol), Belcher said. The investigators studied heart rhythms in both the working heart and in cultured heart muscle cells. In both models, exposure to BPA increased the frequency of arrhythmias, compared to baseline, in females but not in male animals, the authors found. Administration of estrogen alone also increased the frequency of arrhythmias in females.

Arrhythmias were most frequent in the female rats and mice when they received both BPA and estrogen, at levels normally found in female humans.

“We have identified a new possible risk for female heart health, caused by increased levels of estrogens in the body and exposure to the environmental estrogen BPA,” Belcher said.

BPA is found in polycarbonate-plastic baby bottles, refillable water bottles and food containers as well as the linings of metal food cans. Last year the U.S. Food and Drug Administration said more research on the safety of BPA is needed.

Arrhythmias occur when the heart beats too slowly or too fast or when it skips heartbeats. These heart rhythm irregularities can cause fatigue, lightheadedness, fainting or sudden cardiac death. If a fast heart rate affects the heart’s ability to pump, it can cause a heart attack.

The study’s lead author, Hong-Sheng Wang, PhD, assistant professor at the University of Cincinnati, will present the results.

Reference: The Endocrine Society, Bisphenol A exposure increases risk of abnormal heart rhythms in female rodents, 10-Jun-2009

BPA: Our exposure to controversial chemical may be greater than dose considered safe

Baby bottle

People are likely being exposed to the commonly used chemical bisphenol A (BPA) at levels much higher than the recommended safe daily dose, according to a new study in monkeys. The results will be presented Thursday at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.

“BPA is now known to be a potent estrogen,” said Frederick vom Saal, PhD, a co-author of the new study and a professor of biological sciences at the University of Missouri-Columbia. “Human and animal studies indicate it could be related to diabetes, heart disease, liver abnormalities, miscarriage and other reproductive abnormalities, as well as prostate and breast cancer.”

The U.S. Food and Drug Administration (FDA) declared BPA is safe based on estimates that people consume only small amounts each day from food. However, recent research indicated that U.S. adults are exposed to more BPA from multiple sources than previously thought, vom Saal said.

BPA is found in polycarbonate plastic food and beverage containers, such as water and infant bottles, as well as in the epoxy resin lining of cans and other sources. The chemical can leach into food and beverages, according to the National Institutes of Health, which funded the study by vom Saal and colleagues.

“Between 8 and 9 billion pounds of BPA are used in products every year,” vom Saal said.

In their study, he and his colleagues fed five female adult monkeys an oral dose of BPA (400 micrograms per kilogram of body weight). This amount is more than 400 times higher than the amount that the U.S. Food and Drug Administration (FDA) estimates that human adults are exposed to and 8 times higher than the estimated safe daily amount to consume, according to vom Saal.

Yet the blood levels of biologically active BPA over the next 24 hours were lower in the monkeys than the average levels found in people in the United States and other developed countries, vom Saal said. For levels to be higher in people when measured, their exposure dose must be greater than that given to the monkeys, he explained.

“These results suggest that the average person is likely exposed to a daily dose of BPA that far exceeds the current estimated safe daily intake dose,” vom Saal said.

He said that BPA exposure must come from many unknown sources, in addition to food and beverage containers. Like drugs, BPA acts in pulses, with each exposure creating a high-level pulse before it is cleared in the urine, according to vom Saal.

The researchers are continuing the study in more monkeys, but vom Saal said they do not expect to get different findings because the data in the first five animals were “very consistent.” The species of monkey that they used (rhesus) metabolizes BPA similar to humans, he added.

Reference: The Endocrine Society, Our exposure to controversial chemical may be greater than dose considered safe, 10-Jun-2009