You may have seen the label, “B.P.A.-free” on the packaging of plastic products such as baby bottles or reusable water bottles. Perhaps you have also seen or read news reports discussing the potential health hazards from BPA exposure. Scientists have been investigating the effect of a common chemical, bisphenol A or BPA, which has long been considered safe, on people’s health. Studies conducted in the 1990s first suggested that low doses of BPA might be hazardous to people’s health. Since then, researchers have been investigating the effects of low doses of BPA on animals and to some extent, humans. Their findings are controversial, leading to conflicting reports and causing the Food and Drug Administration (FDA) to reevaluate the safety of BPA. But what is BPA? And why might it be harmful?
Bisphenol A (BPA) is chemical that is used to make polycarbonate plastics and epoxies. Polycarbonate plastic is a hard, clear, almost shatterproof plastic that is found in many common items such as reusable water bottles, CDs, computers and sports safety equipment. BPA was first used for commercial applications in the 1950s, and since that time the number of uses for BPA has grown rapidly. Today, many common products are made using BPA; BPA is used in the coating inside food and drink cans, adhesives, and circuit boards. Due to the many uses for BPA, there is over 6 million pounds a year produced in the United States alone. Manufacturers like to use BPA-based polycarbonate because it is so tough, almost unbreakable, and holds up well over time. The recent health concerns over BPA have led some manufacturers to use alternatives to BPA-based polycarbonate; some have returned to using glass or stainless steel, while others have developed polycarbonate-like plastics that do not use BPA. However, these new plastics are usually more expensive than the BPA-containing polycarbonate. BPA is also used in the coating inside food and drink cans and this may be unlikely to change; manufacturers say there is no safe alternative to these BPA-containing epoxies.
BPA did not have any immediate harmful effects when tested for acute toxicity. However, the effect of continuous exposure to low doses of BPA has some scientists concerned. BPA can actually leach out of can linings or plastic containers into the food or drinks they are holding, so that most people are exposed daily to small amounts of BPA. In fact, over 90% of the U.S. population has detectable levels of BPA in their urine, according to the Centers for Disease Control and Prevention (CDC).
Many studies have been done on BPA in rodents and have shown that BPA is an endocrine disrupter and acts like the hormone estrogen. In rats that do not produce estrogen, BPA can restore estrogen-dependent behaviors and physiological processes. In other animal studies, BPA caused accelerated puberty, tumor development, and behavior changes in the offspring of mothers fed BPA. Doctors and scientists still don’t know if or how this estrogenic activity could affect human health. Studies have also suggested that BPA may cause early developmental defects and other hazardous health conditions in adults such as obesity, liver damage, and diabetes.
Much of the controversy surrounds the determination of a safe dose of BPA for humans. The Environmental Protection Agency (EPA) has set a reference dose of 0.05 mg/kg per day; exposure below this level is not thought to cause any harmful health effects. For a 150-pound person, this is about 3.4 mg of BPA per day. If you consider that a peanut weights about 0.5 grams, then this would be about 1/150th of that peanut. Estimates of BPA intake range from 0.6 to 71.4 ug/day, so most people are well below the reference dose. However the reference dose is only an estimate of safe levels based on studies in animals. Different animals have been tested in order to determine a safe dosage, including mice, rats, and dogs. Each animal is different in terms of how BPA is metabolized and excreted and so the animal studies may not be able to accurately determine a safe dose for humans. Some researchers believe the reference dose may be too high, that exposure to BPA at current levels may already be causing adverse health effects in humans. But there is little data to support one way or the other; almost all of the current studies have been done using animal models.
The first human study measuring the correlation between BPA levels and disease was recently conducted. Urine levels of BPA were measured in 1500 adults. The participants were also asked if they had any known diseases such as cancer, liver disease, diabetes, etc. They found that the adults with high urine levels of BPA were also more likely to have heart disease or diabetes. This is the first study to suggest a link between diabetes and heart disease and high levels of BPA in humans. However, this data only shows a correlation between high BPA levels and diabetes and heart disease, there is no data showing that BPA actually caused these diseases. For example, studies suggest that a major route of BPA exposure may be through cans, so that a person that drinks a lot of soda would be expected to have high levels of BPA. Drinking a lot of soda may also be a risk factor for these diseases and the high levels of BPA may have nothing to do with causing disease. As the first study to measure BPA levels and human disease, its findings are very interesting, but must be followed up by additional studies to determine if BPA exposure is a risk factor for diabetes and heart disease.
The Final Verdict?
The Food and Drug Administration (FDA) maintains that BPA can be safely used for food packaging and that the recent studies are still not conclusive about the effect of BPA on human health. In April, however, the Canadian government banned the use of BPA in baby bottles. Researchers and officials still disagree about the possibility of harmful effects from BPA. It will likely take many additional tests and studies to come to a definite answer on a safe level of BPA exposure for humans.
Until a verdict is reached, it appears that with some food and drink storage products, you have a choice: BPA-free options, especially for baby and water bottles, are becoming widely available if you choose to make the switch. However the current data is controversial and it will take time and more studies to determine what effect, if any, BPA has on human health.
–Dana E. Christofferson, Harvard Medical School
For More Information:
New York Times: Agency Affirms Plastics Safety, as Study Raises Questions:
< http://www.nytimes.com/2008/09/17/health/17plastic.html >
New York Times: Canada Takes Steps to Ban Most Plastic Baby Bottles:
< http://www.nytimes.com/2008/04/19/business/worldbusiness/19plastic.html >
Centers for Disease Control and Prevention:
< www.cdc.gov >
The Environmental Protection Agency:
< www.epa.gov >
Lang IA, Galloway TS, Scarlett A, Henley WE, Depledge M, Wallace RB, Melzer D. (2008). Association of urinary bisphenol A concentration with medical disorders and laboratory abnormalities in adults. JAMA. 300 (11): 1303-10.