You may have noticed a growing frequency of this label on your tupperware containers and plastic water bottles: “BPA-free.” Let’s be serious, you’ve likely been living under a rock if you haven’t. “BPA-free” has, for the past few years, been the answer to the growing concern of chemical-leaching plastics. The word “leaching” alone is enough to make your food unappetizing so, of course, “BPA-free” sounds much better, right? Turns out BPA-free plastics have their share of negative side-effects, too.
Bisphenol A (BPA) is a compound found in many plastic products you may encounter on a daily basis – food packaging, plastic food storage, lining on the inside of canned foods, thermal paper receipts, dental fillings, dust from laminate flooring, and even children’s toys and baby bottles. When the plastic becomes damaged, some of the compound can leach into your foods or liquids and then is consumed. Because of it’s chemical structure it is what’s called an “estrogenic” molecule, meaning it is capable of mimicking estrogen and interacting with the estrogen receptors in the body.
This can have serious side-effects: early puberty, infertility in both men and women, decreased sperm count and sperm quality, polycystic ovarian syndrome (PCOS), and hormone-dependent cancers, such as breast and prostate cancers ². Logically, when many of these side-effects started being attributed to BPA-leaching in their products, many companies switched to BPA alternative plastics. Unfortunately for many of those companies, many of those alternatives have been found to affect sperm and egg production in mice.
By accident Patricia Hunt’s lab at Washington State University found a leaching problem with Bisphenol-S (BPS), a common BPA alternative. They had set up an experiment to study the effects of BPA, using BPA-free plastic cages so their control group wouldn’t be contaminated. After awhile, however, they started to notice genetic anomalies in the controls that were similar to the experiment group, which were receiving small doses of BPA. Theoretically this shouldn’t be possible, so they started testing their cages and found the BPS was leaching, causing similar effects as the BPA they were trying to study¹.
The problem lies in the structure: the BPA-alternatives, which are all still bisphenols, maintain the same basic structure with a few substitutions or additions tacked on. It’s kind of like humans: we all have a head with ears, lips, nose, and a set of eyes. However, exactly how those parts look is a little different, but for the most important functions they work much the same.
This got the ball rolling on a whole new study: they compared multiple types of BPA-alternatives and found they decreased sperm count and increased the number of eggs and embryos with abnormal numbers of chromosomes (normally they are in pairs). These consequences are due to a failure in recombination: when an egg and a sperm meet, they combine their respective sets of DNA which pair up according to type and go through a slicing process in which some bits of DNA are exchanged between the maternal and paternal DNA copies. This plays a pretty crucial role in evolution, increasing the diversity of the gene pool. Failure of this process could have disastrous effects on a species.
In the females, the abnormal eggs are not destroyed by the body; in males, there is a “checkpoint mechanism” which destroys these defective sperm, consequently lowering the count. To make matters worse, the study found these effects due to the bisphenols can be passed on to the next generation and can amplify if the successive generations are also exposed.
So are we doomed? Perhaps not. Thankfully the study also found that if bisphenol exposure can be removed, the production of eggs and sperm returned to normal after four generations in mice. It is yet unknown if this is possible in humans, but it is at least a spark of hope.
In the paper they state all “bisphenols should be considered germline toxicants*,” so it seems the best advice is try to limit your plastic exposure when possible by opting for glass, paper, and can-free alternatives.
¹Horan et al., Replacement Bisphenols Adversely Affect Mouse Gametogenesis with Consequences for Subsequent Generations, Current Biology (2018), https://doi.org/10.1016/j.cub.2018.06.070
²Konieczna, A., A. Rutkowska, and D. Rachoń. “Health Risk of Exposure to Bisphenol A (BPA).” Rocz Panstw Zakl Hig. 2015:66(1): 5-11.
*germline toxicant: a chemical or substance which negatively affects the function or production of the cells (germ cells) which give rise to the gametes (eggs and sperm).