BPA and Semen Quality
Bisphenol A (BPA) is a high production volume chemical that has been a topic of much debate in the news over the past few years. This ubiquitous chemical has endocrine disrupting/mimicking properties and has been associated with adverse health outcomes in animals and humans, including metabolic syndrome (obesity, diabetes), neurobehavioral deficits and adverse reproductive health outcomes. We are exposed daily to BPA through food contact materials, for example drinking out of polycarbonate (PC) plastic water bottles, eating food stored and heated in PC containers, and previously infants were exposed through drinking from baby bottles, but due to consumer demand PC baby bottles were taken off the shelves and replaced with BPA free bottles. BPA is also used in the manufacture of epoxy resin and lacquer lining of canned food and beverages. Other sources include dental sealants and white composite fillings and recently, thermal receipt paper handled daily in supermarkets, ATM machines, gas stations, etc was found to be an additional source of exposure to BPA through dermal absorption (Ehrlich S. et al. 2014).
In 2010, BPA was labeled toxic in Canada and as a precautionary approach, the import, sale and distribution of BPA-containing baby bottles was banned in Canada. In the USA, however, BPA is still considered safe at levels found in consumer products. The Food and Drugs Administration (FDA) is however currently reevaluating their stance based on multiple studies published in recent years that include in vitro, animal and human studies. With regard to human reproduction, the level of concern has been that of negligible to minimal concern, due to the absence of human evidence that shows it is unsafe. A call for more epidemiological studies was made to reach a definitive conclusion. Our goal was to therefore examine the association between BPA and semen quality parameters. Since studying human reproduction is challenging in naturally conceiving couples, particularly for women, our group studied the association between BPA and early reproductive health outcomes using a fertility cohort undergoing assisted reproductive technologies (ART). We recruited 190 men attending the Massachusetts General Hospital (MGH) Vincent Fertility Clinic between 2000 and 2004. These men were partners in subfertile couples seeking fertility treatment. We examined these associations cross-sectionally and found that increased urinary BPA concentrations collected on the same day as a semen sample were associated with suggestive declines of 23% and 13% in sperm concentration and sperm morphology, respectively, as well as a 10% increase in sperm DNA damage that were statistically significant (Meeker J, et al. 2010). Urinary BPA concentrations in our cohort were slightly lower but comparable to the general US population levels (CDC National Health and Nutrition Examination Study 2005-2006). Our findings are consistent with animal studies that showed adverse effects of BPA on Sertoli cell function and sperm production. An occupational study in 218 male workers from epoxy resin factories in China, (Li DK et al, 2011) similarly found significantly decreased semen quality parameters in the high BPA exposure group. Taken together these recent animal and human findings build a body of literature that can help to inform policy makers in their reevaluation of the level of concern of BPA in relation to male fertility in the coming year.
One main critique of our study design may be that men attending a fertility clinic are not representative of the general population and thus the abovementioned changes in semen parameters may not be as relevant to a healthy fertile man. Male reproduction, however, has been declining over the past few decades and while the decreases in semen quality seen in an average healthy man of fertile age may not impact fertility on an individual level, population shifts in semen parameters to the left can significantly impact those men who are at the lower end of the normal range of semen parameters, thus increasing the proportion of infertile men in the general population over time. This is a growing public health concern. According to Carlsen et al in 1992, there has been a global decline in sperm counts of 40% over the second half of the 20th century. While controversial, due to the inherent limitations of studying historical and ecological data, the study findings were later confirmed by Swan et al. and in 2000, when the question of declining sperm counts was revisited and the analyses expanded to include additional studies published since 1990, the decline in global sperm counts was again confirmed. This observed decline in semen quality has been attributed to environmental factors that may explain the geographical and temporal patterns of decline over a relatively short period of time. It is therefore necessary to carefully assess the impact of BPA and other endocrine disrupting chemicals on male infertility.
Ehrlich S, Calafat AM, Humblet O, Smith T, Hauser R. 2014. Handling of thermal receipts as a source of exposure to bisphenol A. JAMA Feb 26;311(8):859-60.
Meeker JD, Ehrlich S, Toth TL, Wright DL, Calafat AM, Trisini AT, et al. 2010. Semen quality and sperm DNA damage in relation to urinary bisphenol A among men from an infertility clinic. Reprod Toxicol 30: 532-539.
Li DK, Zhou Z, Miao M, He Y, Wang J, Ferber J, et al. 2011. Urine bisphenol-A (BPA) level in relation to semen quality. Fertil Steril 95: 625-630.
Carlsen E, Giwercman A, Keiding N, Skakkebaek NE. 1992. Evidence for decreasing quality of semen during past 50 years. BMJ. 1992 Sep 12;305(6854):609-13.
Swan SH, Elkin EP, Fenster L. 2000. The question of declining sperm density revisited: an analysis of 101 studies published 1934-1996. Environmental Health Perspectives 108:961-966
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