BPA exposure disrupts human egg maturation; may explain some fertility problems

		IMAGE: Images of eggs examined in this study show a properly formed spindle structure with aligned chromosomes (image A) and eggs with spindles of various abnormal shapes and misaligned chromosomes after... Click here for more information.

As many as 20 percent of infertile couples in the United States have unexplained reasons for their infertility. Now, new research led by Catherine Racowsky, PhD, director of the Assisted Reproductive Technologies Laboratory at Brigham and Women's Hospital (BWH), shows that exposure to BPA (Bisphenol-A) could be a contributing factor as to why some infertile couples are having difficulty conceiving. The study will be published online on July 31, 2013 in the journal Human Reproduction.

"To our knowledge, this is the first study that has shown that BPA has a direct effect on egg maturation in humans," said Dr. Racowsky. "Because exposure to BPA is so ubiquitous, patients and medical professionals should be aware that BPA may cause a significant disruption to the fundamentals of the human reproductive process and may play a role in unexplained infertility."

The randomized trial examined 352 eggs from 121 consenting patients at a fertility clinic. The eggs, which would have otherwise been discarded, were exposed to varying levels (20 ng/ml, 200 ng/ml and 20 µg/ml) of BPA in a laboratory setting. An egg from each patient was not exposed to BPA and served as the control. Researchers then examined the eggs and found that exposure to BPA caused:

• A decrease in the percentage of eggs that matured.
• An increase in the percentage of eggs that degenerated.
• An increase in the percentage of eggs that underwent spontaneous activation, the abnormal process when an egg acts as though it has been fertilized, even though it has not been.

As the BPA dose increased, there was a decreased likelihood of maturity, an increased likelihood of degeneration and an increased likelihood of spontaneous activation. Additionally, among the mature eggs, there was a significant trend toward a decreased incidence of bipolar spindles and aligned chromosomes with an increased dose of BPA. Researchers note that these results are similar to the previous research examining the impact of BPA exposure on animal eggs.

Racowsky said, "Our data show that BPA exposure can dramatically inhibit egg maturation and adds to a growing body of evidence about the impact of BPA on human health. I would encourage further research to gain a greater understanding of the role BPA plays in infertility."

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Study: Chemical exposure and pollutants may impact ability to conceive

Researchers at the National Institutes of Health are reporting that couples with high levels of PCBs and similar environmental pollutants take longer to conceive a child.

PCBs (polychlorinated biphenyls) are chemicals that have been used as coolants and lubricants in electrical equipment. They are part of a category of chemicals known as persistent organochlorine pollutants and include industrial chemicals and chemical byproducts as well as pesticides.

The compounds are also resistant to decay, and may persist in the environment for decades. Some, known as persistent lipophilic organochlorine pollutants, accumulate in fatty tissues. Another type, called perfluorochemicals, are used in clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and the insulation of electrical wire.

Exposure to these chemical pollutants is known to have a number of effects on human health, but their effects on human fertility-- and the likelihood of couples achieving pregnancy-- have not been extensively studied.

To conduct the study, the researchers enrolled 501 couples from four counties in Michigan, and 12 counties in Texas, from 2005 to 2009. Couples provided blood samples for the analysis of organochlorines (PCBs) and perfluorochemicals (PFCs). Women kept journals to record their monthly menstrual cycles and the results of home pregnancy tests. The couples were followed until pregnancy or for up to one year of trying.

For each standardized increase in chemical concentration the researchers measured, the odds of pregnancy declined by 18 to 21 percent for females exposed to PCB congeners 118, 167, 209, and the perfluorchemical, perfluorooctane sulfonamide. Perfluorooctane sulfonamide is one of a broad class of compounds known as perfluoroalkyls, which have been used in fire fighting foams.

With increasing exposure, the odds for pregnancy declined by 17 to 29 percent for couples in which males were exposed to PCB congeners 138, 156, 157, 167, 170, 172, and 209 and to DDE, produced when the pesticide DDT degrades in the environment. DDT is banned for use in the United States, but is still used in some countries.

The investigators noted that they cannot rule out that some of the delays they observed may have been due to exposure to multiple chemicals. They added that these associations would need to be confirmed by other researchers.

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