Sex and Plastics: A Connection You Should Pay Attention To!

Sex and Plastics: A Connection You Should Pay Attention To!

By Lori Cooper, MD

There is a lot of information coming out in the news about the dangers of substances in the environment that can have a negative effect on our endocrine or hormone systems. In particular, attention has been focused on bisphenoyl[bis-fē-nŏl] A (BPA) and its reported effects on the reproductive hormones, specifically estrogen (the main female sex hormone).

What is BPA?

Bisphenoyl A (BPA) is an industrial chemical that is used to make hard plastics and epoxy resins, which often coat the insides of metal cans. It was first synthesized in 1891, and by the 1930s its use as a synthetic (manufactured) estrogen was being explored, due to its estrogen-like properties. However, at this time diethylstilbestrol [dī-eth'il-stil-bes'trol] (DES) also came to the marketplace as a synthetic estrogen, and so BPA fell out of favor. In the 1950s, BPA was rediscovered as a building block of polycarbonate plastics used for food and beverage storage. Today it is one of the most abundantly produced chemicals worldwide. BPA-containing plastics are popularly used due to their clear and shatter-resistant properties for things such as headlights, water bottles, baby bottles, automobiles, sports equipment and coatings on CDs, DVDs, electrical equipment and medical devices. In fact, it would be extremely hard not to come into contact with BPA-containing products.

Why is BPA a health concern?

BPA has been linked with a number of health conditions. It is referred to as an “endocrine disruptor,” which means that it can interfere with the function of some of the hormones that your own body produces. This can lead to adverse changes in reproduction, development, neurological function and responses of the immune system. BPA was traditionally considered a “weak” estrogen, because it does not act as strongly as our body’s own estrogen. Estrogen is important in maintaining the function of reproductive organs and is also involved in bone health, protein synthesis, cholesterol metabolism, mental health, sexual desire and many other systems. As we learn more about BPA, we are finding that it may actually be a more potent estrogen mimic than was previously thought.

How does BPA act on the body?

BPA is considered a xenoestrogen (zē-nō-ĕs-trō'jin), which means “foreign estrogen.” Xenoestrogens are man-made compounds that mimic the effects of natural estrogens in the body. While BPA was thought to be 1,000 to 10,000 times less potent than estradiol [es-truh-dahy-awl], the main form of estrogen in reproductive years, in some cases it may be just as potent as estradiol. Additionally, the metabolites, or “break down” products of BPA may potentially be stronger xenoestrogens than BPA itself. BPA binds to various cells like an activator switch and triggers many of the same chemical changes as natural estrogen in the body. While it was initially thought that BPA acted only through cellular proteins called estrogen receptors (which act as signaling switches on cells), we have also learned that BPA can exert its estrogenic effects through other receptors as well.

What does BPA exposure cause in humans?

Fetuses, infants and children are most likely to be affected by BPA, even at levels of exposure below the established safety levels. Examples of the effects of BPA during these periods include abnormal pubertal development, behavioral changes, asthma, and impaired immune system, thyroid and adrenal functions. Because BPA exhibits hormone-like effects and acts in a similar way to estrogen, it can potentially interfere with many different systems in the body. Research into the effects of BPA in the early years of life has shown that exposure to BPA may induce changes that carry on into adulthood, although currently little is known about these effects.

Researchers are now trying to explore the link between BPA and diseases such as breast and prostate cancer, recurrent miscarriages, premature deliveries and abnormal semen production. In addition, they are also exploring the association of BPA with diabetes, cardiovascular disease, obesity and abnormal liver function. A great deal of what we know is based on animal studies, and sometimes attempts to establish the same findings in humans can be difficult. More research in this area is needed and is presently underway to examine how BPA acts and its consequences on our health in all stages of life.

It is also important to be aware that BPA is only one of many endocrine disruptors to which we are exposed. Plastics can often contain many other chemicals with estrogen-like activity. Whether BPA acts independently in exerting its effects, or has additive effects in the presence of these other disruptors, remains to be seen. Therefore, manufacturing “BPAfree” products is unlikely to limit risk entirely.

How does exposure to BPA occur?

Despite its durable properties, BPA is prone to leaching out of the very substance it makes. Exposure most often occurs by ingesting BPA from food and drink containers. Residual BPA that does not become bonded with the other compounds that make plastic can slowly seep out over time. This particularly happens when BPA-containing plastics are heated, microwaved or autoclaved. Given how prevalent BPA is in our surroundings, it is not surprising that most people have detectable levels in their bodies. Research has shown that BPA can be measured in 95 percent of urine samples analyzed in the U.S.A.!

How much BPA exposure is safe?

In the 1980s, the U.S. Food and Drug Administration (FDA) set the daily safety level for BPA at 50μg/kg body weight, based on prior experiments conducted in rodents. While this amount was based on the lowest levels at which cancer was observed to occur in animals and then divided by a factor of 1000 (to allow for a very large safety margin), other non-cancerous effects of BPA can be seen at levels well below this threshold. Levels of BPA exposure vary throughout life, and the fetal, infant and childhood periods represent more vulnerability to the effects of BPA.

What should I be doing about my exposure to BPA?

Precautions surrounding BPA exposure are most important when it comes to the developing fetus, infants and young children. Tips to help limit BPA exposure include:

  • Avoid microwaving polycarbonate plastic food and drink containers
  • Use only BPA-free baby bottles
  • Decrease consumption of canned foods and beverages with epoxy resins
  • Avoid plastic containers with number “7” recycling code on the bottom, as these often contain BPA
  • Try to use glass, porcelain or stainless steel containers

What regulations have come about concerning BPA?

In 2008, the safety of BPA came into question by the National Institutes of Health, resulting in some retailers withdrawing their polycarbonate products from the market. In 2010, the FDA warned of concern to fetuses, infants and children. That same year, Canada became the first country to declare BPA a toxic substance. Since then, Canada, the European Union and the U.S. have banned BPA in baby bottles. However, in 2012 the FDA decided against a ban of BPA from food packaging, despite increasing evidence of the harmful effects of BPA. While the picture is not completely clear and we need more research to help understand BPA’s effects, be cautious about your choice of food container, of what you use to heat your food in and from what you drink your liquids!

Dr. Lori Cooper is an Endocrinology Fellow at the University of Washington in Seattle. She is board certified in internal medicine. Dr. Cooper is currently involved in research examining the effects of testosterone on the prostate gland. She is interested in all aspects of general endocrinology and has a particular interest in male and female reproductive disorders as well as disorders of the adrenal glands.