BOSTON, USA: Researchers from the U.S. have found that exposure to bisphenol A (BPA), a chemical used to manufacture dental sealants, among other uses, significantly impairs human egg maturation. They believe that the findings may contribute to a better understanding of the decrease in fertility among both women and men in recent decades. In a randomized trial of 121 patients who underwent infertility treatment cycles at Brigham and Women’s Hospital from March 2011 to April 2012, the researchers found a dose–response association of BPA exposure with altered human egg maturation in vitro.
They exposed 352 clinically discarded oocytes to different concentrations of BPA in a laboratory setting and found that there was a decrease in the percentage of oocytes that progressed as the BPA dose increased. In addition, they observed an increase in the percentage of oocytes that were degenerated. Among other findings, they reported that oocytes exposed to 20 µg/ml BPA progressed significantly more slowly than controls did.
“To our knowledge, this is the first study that has shown that BPA has a direct effect on egg maturation in humans,” said Dr. Catherine Racowsky, lead researchers and director of the hospital’s Assisted Reproductive Technologies Laboratory. “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.”
BPA is found in a wide variety of daily consumer products, such as food cans, beverage containers, plastic dinnerware, automobile parts and toys. Although the industrial compound has been shown to disrupt the endocrine system in several in vitro and in vivo studies, the mechanism underlying this effect is largely unknown. In the scope of the National Health and Nutrition Examination Survey, a program designed to assess the health and nutritional status of adults and children in the U.S., researchers found BPA in the urine of more than 90 percent of participants. It has also been found in various human fluids, including follicular fluid in a Japanese study in 2002.
According to the Centers for Disease Control and Prevention, 6.7 million women aged 14 to 44 in the U.S. have impaired ability to fall pregnant or carry a baby to term. Over 7 million women in this age group have used infertility services. The researchers added that approximately 20 percent of infertile couples in the country have unexplained reasons for their infertility.
The study, titled “Bisphenol-A and Human Oocyte Maturation in vitro,” was published online on July 30 in the Human Reproduction journal.