June 18, 2009
A study released this week by researchers at the University of Cincinnati says that exposure to bisphenol A may increase heart disease in women.
<p>Bisphenol A (BPA) is the chemical building block of polycarbonate plastics and is used in countless consumer products including food and beverage containers, kitchen appliances, electronics, and packaging and is used to make resins that line food and drink cans.</p><p>Research by Scott Belcher and colleagues in the university's department of pharmacology and cell biophysics has found that environmentally available levels of BPA -- a synthetic chemical known to mimic the behavior of estrogen -- can disrupt normal heart muscle function and prompt arrhythmia or irregular heartbeat.</p><p>BPA has come under increasing scrutiny by medical researchers for its endocrine-hormone-disrupting potential -- effects that include interference with reproductive, egg and fat cell development, as well as with thyroid hormone and neurological functions. The chemical has also been linked to conditions that can prompt obesity and diabetes.</p><p>Additional cause for concern is the fact that these adverse effects can occur at very low levels of exposure.</p><p>"Levels of bisphenol A identified in human blood that would be in direct contact with the heart" can produce the effects seen in our research, said Belcher, speaking from Washington, where this research was presented at the June 10-13 Endocrine Society annual meeting.</p><p>While it creates plastics so durable they are used in sports gear, motor vehicles, shatterproof lenses as well as in baby bottles and toddlers sippy cups, the chemical can leach from finished products. These plastics and resins are so widely used that researchers studying the chemical describe BPA as ubiquitous. And although BPA does not last long in the environment or the human body, because it is so prevalent, current exposure in the U.S. is considered virtually continuous.</p><p>Monitoring by the U.S. Centers for Disease Control and Prevention (CDC) has found BPA in nearly 95 percent of the Americans tested. A recent <a href="http://www.hc-sc.gc.ca/fn-an/securit/packag-emball/bpa/bpa_survey-enquete-can-eng.php">study by Health Canada</a> found BPA in 96 percent of the canned soft drinks it tested -- a study that covered 84 percent of all soft drinks sold in Canada -- at levels equivalent to 500 times what are considered normal estrogen levels.</p><p>Belcher's study showed that environmentally relevant, low levels of BPA can interfere with the genetic receptors that help regulate cardiac muscles, resulting in an increased frequency of irregular heartbeat. As an estrogenic compound, explains Belcher, the BPA interferes with how the heart muscle cells process calcium, a key factor in maintaining normal, healthy heartbeat. Due the specific ways in which the female body responds to estrogenic substances, this effect occurred in females rather than males.</p><p>One in three women in the U.S. suffer from cardiovascular disease, and <a href="http://www.americanheart.org/downloadable/heart/1236184538758WOMEN.pdf">women account for over 50 percent of the U.S. deaths</a> from heart attack, so this finding could have wide ramifications. </p><p>According to the American Heart Association, women have a higher rate of death from a repeat -- rather than first -- heart attack, making any factors that could increase the risk of subsequent heart attack of particular concern.</p><p>Thus far, the adverse impacts of BPA on cardiac muscle cells have been seen in cells isolated from rat and mouse hearts. But Belcher says the genetic mechanisms affected should work the same way in the human heart. A statement on endocrine-disruption chemicals -- such as BPA -- just released by the <a href="http://www.endo-society.org/journals/ScientificStatements/upload/EDC_Scientific_Statement.pdf">Endocrine Society</a> notes that the way these chemicals work is comparable in wildlife and in humans and in both live-animal and cell-culture experiments. Belcher's group is in the process of looking at cells isolated from human heart transplant samples.</p><p>Bisphenol A is currently approved by the U.S. Food and Drug Administration for use in food contact and other consumer products. But as evidence of the chemical's potential adverse health impacts grows, there are increasing efforts to regulate the compound.</p><p>Numerous states have introduced bills that would bar BPA from infant and children's products, but thus far only two have passed, one in Chicago, the other in Minnesota. However, a number of U.S. retailers have withdrawn such products voluntarily, among them Wal-Mart and Toys R Us. Canada has banned BPA from baby bottles sold there and now includes BPA on its list of toxic substances.</p><p>The chemical and plastics industry maintains that BPA is safe, as does the North American Metal Packaging Alliance, whose members use BPA in food-can lining. "The science supporting the safe use of epoxy liners in food contact applications is both extensive and extensively analyzed," said a <a href="http://www.metal-pack.org/docs/pdf/00046353.PDF">statement released by NAMPA</a> on May 30 in response to news media reports of a <a href="http://www.washingtonpost.com/wp-dyn/content/article/2009/05/30/AR2009053002121.html">plastics and packaging industry meeting</a> convened to craft a campaign to defend BPA safety. </p><p>"The scientific evidence supporting the safety of bisphenol A has been repeatedly and comprehensively examined by government and scientific bodies worldwide. In every case, these assessments support the conclusion that bisphenol A is not a risk to human health at the extremely low levels to which people might be exposed," says a <a href="http://bisphenol-a.org/pdf/FactSheet-experts.pdf">statement</a> from the Polycarbonate/BPA Global Group of the American Chemistry Council.</p><p>Responding specifically to Belcher's study and other as-yet-unpublished research presented at the Endocrine Society meeting, the ACC said, "Bypassing the scientific process in favor of sensational press releases is a scare tactic that will not promote public health." The ACC also questions the relevance to human health of BPA research conducted with animals.</p><p>"It should be noted that the Endocrine Society's conclusions directly conflict with the findings of authoritative scientific reviews," the ACC said in an additional statement released June 10. "In fact, the International Union of Pure and Applied Chemistry (IUPAC) has stated it is 'somewhat reassuring that after substantial research in the past decade, there have been no conclusive findings of low-level environmental exposures to EAS [endocrine active substances] causing human disease."</p><p>While not confirmation of any direct cause and effect, research published last year in the <a href="http://jama.ama-assn.org/cgi/content/full/301/7/721"><em>Journal of the American Medical Association</em></a> found that people exposed to higher levels of BPA are more likely to develop cardiovascular disease than those who were not. This study was based on samples from nearly 1,500 adults collected by the CDC's National Health and Nutrition Examination Survey.</p><p>"For women, exposure to any environmental estrogens could be very important after a heart attack," said Belcher. Many women also experience arrhythmia during pregnancy, and the severity of an existing arrhythmia can worsen during pregnancy, so anything that would increase such risks would be of concern to both maternal and fetal health.</p><p>Given the strong evidence of multiple adverse health impacts of endocrine-disrupting chemicals such as bisphenol A, the Endocrine Society -- which has over 14,000 members from over 100 countries -- recommends decreasing exposure to these chemicals. Meanwhile, the FDA is continuing its own review of BPA safety.</p>
Keep reading... Show less