Bisphenol A
Chester J. Zelasko, Ph.D. | July 22, 2008

If you’ve paid any attention to the news, you know that plastic bottles have come under scrutiny--not only beverage bottles, but sippy cups, baby bottles, and the lining of all types of cans. The culprit is a resin called bisphenol A (BPA) that is used in the manufacture of polycarbonate bottles and can linings. This Newsletter will examine the issue of BPA and whether there’s any real evidence of harm to humans.

The Concern
Due to its chemical structure, BPA can mimic the female hormone estrogen and can weakly bind to estrogen receptors. The question is why could this be a problem? Estrogen-like activity attributed to exposure to BPA has been associated with health issues from cancer to obesity to growth issues in children. We’ve all had exposure to BPA--95% of all Americans have measurable amounts of BPA in their urine based on testing from the U.S. Centers for Disease Control (1).

Should we be concerned? It’s very difficult to know for certain. The plastics manufacturers and the scientific community put forth only their own points of view. As you might expect, the manufacturers suggest that their research demonstrates that plastics are safe. On the other hand, the anti-BPA research community hasn’t presented their case as clearly as they might.

One body of scientific research focuses on the effects of BPA on animals and humans. Breast cancer, abnormal genital development, and prostate growth are some of the health problems attributed to BPA exposure in animal studies. The problem is that the type and nature of the exposure varies. For example, the administration of the liquids containing BPA isn’t exactly consistent with typical eating in animal studies. In order to dose every animal the same, they use a procedure called oral lavage. Think of it this way: a tube is forced down the throat to directly put the liquid into the stomach. It’s the only way to get identical amounts into the animals, but it’s not what happens in the real world to animals or humans.

In humans, BPA has been thought to be related to infertility. In a study done in Japan, researchers examined several groups of women: normal weight, obese, and some with polycystic ovary syndrome (POS). All subjects had levels of BPA in their blood, but those with the highest BPA also had the highest androgen levels (male sex hormones) (2). Increased androgens may partially explain infertility. However, in a recent study, researchers could find no association between exposure to BPA and infertility (3).

The other body of research examines the amount of BPA that is actually leached from plastics and the conditions under which they can be released such as heat and liquids (4, 5). After reading the studies, I’m not ready to stop using my plastic coffee mug; the amounts fall well within the current safety limits.

Bottom Line
The research that’s missing on BPA is cause and effect. Human trials are lacking and, because humans live so long, would be difficult to perform. Additionally, in any clinical trial with the potential for negative effects, it’s difficult to gain approval from human-subject committees. The probability is that no long-term human clinical trial will be done. The only way we will ever find out the effects is by epidemiological study. That may tell us general effects but not specific exposure issues.

What I can tell you is that if you want to avoid exposure to BPA, check for the symbol on the bottom of the bottle or cup. Avoid plastics made with the plastic symbol 3, 6, or 7--those can contain the higher amounts of BPA (5). The plastics in soft drinks and bottled water are fine. Based on the research I’ve read, even if you’ve been using a plastic 7 as I have for coffee, the amount you might have been exposed to is relatively low and within the safety limits. And if you want to reduce the 3, 6, and 7 plastic in your children’s lives, I can’t argue with that--you’ll be limiting their lifetime exposure, particularly during their formative years and that may give science time to catch up. As long as you avoid making them paranoid about plastic, there’s no harm done.

Here’s more food for thought. We pick up substances from our environment all the time. When we use cast-iron skillets, we pick up iron. If we cook in aluminum pans, we pick up aluminum. (Remember all the hype about aluminum and Alzheimer’s?) If we live near a forest, we pick up molds and pollen. If we live in a desert, and this is gross, we inhale dried animal feces that become airborne. So the problem is that we will never get to a place where we can avoid every potential danger. While we shouldn’t seek out potential dangers--such as using bottles if they really do leak toxins--we can never avoid them. The idea is to keep your body healthy to combat any natural or man-made toxins--that’s what they’re designed to do.

References:
  1. Lakind JS, Naiman DQ. Bisphenol A (BPA) daily intakes in the United States: Estimates from the 2003-2004 NHANES urinary BPA data. J Expo Sci Environ Epidemiol. Apr 16, 2008 [Epub ahead of print].

  2. Takeuchi, T, et al. Positive Relationship between Androgen and the Endocrines Disruptor, Bisphenol A, in Normal Women and Women with Ovarian Dysfunction. Endocrine Journal. 2004; 51(2), 165-169.

  3. Foster WG Environmental contaminants and human infertility: hypothesis or cause for concern? J Toxicol Environ Health B Crit Rev. 2008 Mar;11(3-4):162-76.

  4. Brede C, et al. Increased migration levels of bisphenol A from polycarbonate baby bottles after dishwashing, boiling and brushing. Food Addit Contam. 2003 Jul;20(7):684-9.

  5. Maragou NC, et al. Migration of bisphenol A from polycarbonate baby bottles under real use conditions. Food Addit Contam. 2008 Mar;25(3):373-83.

  6. Smart Plastics Guide Healthier Food Uses of Plastics. Institute for Agriculture and Trade Policy. October, 2005.
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