Attention, Men: BPA Lowers Your Sperm Count
Guys, here’s a form of birth control you don’t want: plastic.
Scientists have discovered a direct link between exposure to bisphenol-A—a controversial synthetic chemical compound commonly found in plastic water bottles, packaging, toys, and other everyday objects—and lower sperm counts. Researchers also discovered that a key ingredient in birth control pills also lowers male fertility.
It’s the strongest evidence yet that widespread use of these chemicals is harming our ability to conceive children.
“I think this raises concern about any estrogenic exposure and its impact on developing testis,” said the study’s lead investigator, Pat Hunt, a developmental biologist at Washington State University. “We’re changing the mechanics of producing sperm in the male testis.”
The findings, which will be published in early February in the journal PLOS Genetics, vindicate recent consumer activism and laws demanding that manufacturers remove BPA from children’s toys, as well as packaging such as plastic water bottles and can liners. But they also raise worries that exposure to a synthetic hormone called ethinyl estradiol, used in prescription birth control pills, could be harming boys before birth.
Hunt hopes that these results will help create changes in how we test and approve substances for consumer products. “The way we currently test chemicals, the onus is on our government to prove they’re causing harm. The manufacturers get them into the marketplace and our lives [with] some pretty simplistic studies to prove they’re OK,” she said.
In the study, Hunt and her colleagues exposed newborn male mice to elevated levels of BPA or estradiol. They found that the synthetic estrogens were permanently harmful to developing testes, impairing their ability to generate germ cells or sperm.
“Estrogen affected the first wave of cell development right after birth,” said Hunt, “and it never went back to normal in older males.”
To figure out what, exactly, the BPA or estradiol was affecting, the researchers then transplanted germ cells from estrogen-exposed male mice into mice bred with a mutation that left them with testes that didn’t produce sperm but were otherwise healthy.
“They throw a party and no one ever shows up, but otherwise the testis is completely normal,” Hunt said.
If the estrogen had affected something other than the germ cells, the recipient mice would have eventually produced normal amounts of sperm. But instead, the transplantees had the same depressed sperm production as the donors—proving that the estrogens were affecting the germ cells and not some other body system or part.
Hunt said she and her colleagues were surprised at the results. “We thought it was affecting the amount of testosterone or some other aspect of the overall environment,” she said. But “the exposures are changing the stem cells that eventually divide and produce sperm.”
Mice exposed to estradiol, the birth control pill hormone, were more strongly affected than mice exposed to BPA.
To try to clear up some of the conflicting results from other studies of male exposure to endocrine disruptors such as BPA—some studies found them harmful, but others did not—Hunt and her team ran their experiment on mice from three different genetic stocks.
One strain of mice proved completely resistant to the estrogen effect, while the other two were affected. This explains why some past studies have found no negative health effects from BPA on the testis, said Hunt: “They used those mice.”
Regulators should take note, Hunt said.
“How well are the products being tested,” she said, “and what do we actually know about what we put in our bodies and the bodies of our newborns?”