Israeli and American scientists have for the first time uncovered the mechanism by which the chemical compound Bisphenol A, commonly used in the plastics industry, damages human eggs and can harm female fertility.

Studies in recent years have shown a decline in human fertility in both males and females. The new research, which was carried out at Harvard University, and headed by Dr. Ronit Machtinger, a gynecologist at Sheba Medical Center, Tel Hashomer, tried to examine whether human eggs could be damaged by increased exposure to Bisphenol A. The research premise was based on information from previous research on animals that the substances harms various tissues.

Awareness has grown in recent years of the presence of Bisphenol A, especially in the baby bottle industry, in light of concerns that small concentrations of the material could affect babies’ brains and hormonal systems. In December 2010, the Health Ministry instructed hospitals to stop using baby bottles containing Bisphenol A, and in July 2012, the Federal Drug Administration banned further marketing of baby bottles containing the compound in the United States.

However, Bisphenol A is found in many other products, including food storage boxes (marked with the number 7), preservative cans, cold drink cans, CD cases, white dental fillings, plastic eyeglass frames and receipts from cash registers. Urine tests in both the United States and Israel show the presence of the material in 90 percent of those checked; concentrations can also be found in blood, breast milk, amniotic fluid and in the fluid that surrounds the eggs in the fallopian tubes.

The present research collected 242 eggs that had been harvested from 121 women undergoing in-vitro fertilization, who had approved use of the eggs for research purposes. Two eggs from each woman were used, one of which was exposed under laboratory conditions to a maturation culture into which varying amounts of Bisphenol A were inserted. The second egg was used as a control, placed in the same culture but without the Bisphenol A. The results showed that after 30 hours of exposure to Bisphenol A, a greater number of eggs did not mature or began to degenerate. Examination of the chromosomes in the egg showed damage that made proper maturation impossible.

In the group of eggs that were exposed to 20 nanograms per milliliter of Bisphenol A, which is 10 times the average concentration revealed by urine tests of healthy subjects, the rate of eggs that matured and could be used for fertilization was 52 percent, compared to 59 percent in the control group.

In another group of eggs, which were exposed to a quantity of Bisphenol A 100 times the norm, usable eggs declined to 42 percent. When the concentration of the substance was 10,000 times the norm, only 19 percent of the eggs matured.

“As opposed to most cells, including sperm cells, which are created throughout life, the supply of eggs is created in the fetal stage and declines gradually until menopause,” Wachtinger says. “The assumption is that the granulosa cells that surround the egg already contain a basic minuscule amount of Bisphenol A, and we found that continued exposure to concentrations of the substance can harm the supply of eggs and the process of their maturation and female fertility,” she added.

Also participating in the research were Prof. Catherine Racowsky of Harvard Medical School and Prof. Russ Hauser of the Harvard School of Public Health. The study was supported by the National Institute of Health in the United States and by the Environmental Health Fund in Israel. The findings were presented this week at a conference hosted by the latter organization at the Peres Peace Center, and will soon to be published.

According to Wachtinger, follow-up is needed on the effect of Bisphenol A on women’s bodies. “At present the significance of the findings is that long-term exposure to Bisphenol A, even in a low concentration, has possible effects on fertility and should be avoided, for example, by not heating up food in plastic containers in the microwave.”

Recent research has shown that Bisphenol A is transmitted to humans not only through food but also, in minuscule amounts, by touch. French scientists reported in the journal Chemosphere in 2010 in research on pigs that the substance can be transmitted through the skin. In 2011, Harvard scientists reported that cashiers who handled receipts were found to have high concentrations of Bisphenol A in their urine.