Limits in the data
Michael Eisenberg, MD, a urologist and director of male reproductive medicine and surgery at Stanford (Calif.) University Medical Center, often gets questions from patients about how lifestyle and environmental exposures affect male fertility. (In her book, Dr. Swan also discusses how factors such as diet, exercise, smoking, and stress can affect male and female fertility.)
He found the evidence convincing that certain chemicals impact fertility – although, of course, it isn’t ethically possible to do randomized, controlled trials in which some people are intentionally exposed to chemicals to measure the effects. Along with adopting other healthy habits, he advised patients to avoid chemical exposures.
“It’s reasonable to try to eat organic and be mindful of where some of these exposures come from and try to minimize them to the extent possible,” he said.
Rebecca Sokol, MD, MPH, an endocrinologist and expert in male reproductive health, demonstrated the toxic effects of lead on sperm production in studies conducted on rats. But she views low-dose chemical exposure from everyday products as just one aspect of modern reproductive risks, some of which have stronger associations. For example, testosterone therapy impairs sperm production, and finasteride (a medication for male pattern baldness) has been linked to a reversible decline in sperm count.
“When it comes to these ubiquitous chemicals like phthalate and BPA, we explain to the patient that maybe they’re harmful, but we can’t say for sure,” because of the lack of causal data, said Dr. Sokol, professor emerita at the University of Southern California, who was on the panel that drafted the American Urological Association and American Society of Reproductive Medicine guideline on the diagnosis and treatment of male infertility.
Nonetheless, she advised patients to try to reduce exposures. “I don’t see us eradicating all the chemicals that might be bad for us unless we go back to another era. But we can do the best we can to avoid what we can.”
A call to action
Dr. Swan likened awareness of the health threat of chemical exposures to the gradual recognition of the climate crisis as a global imperative. Yet in some ways, the scientific work on chemical effects is even more daunting. The Environmental Protection Agency lists more than 86,000 chemicals on its inventory of chemical substances manufactured or imported into the United States.
Little is known about the potential effects of many chemicals that we inhale, ingest or absorb through our skin, Dr. Swan said. In her book, she noted the impact on wildlife – for example, reproductive abnormalities in frogs, alligators, and birds that were exposed to EDCs.
Yet Dr. Swan also takes solace in the lessons from the animal kingdom. Decades after the pesticide DDT, a neurotoxin and endocrine-disruptor, was banned in the United States in 1972, the bald eagle has made a comeback from near-extinction. She also pointed to a 2018 study which found that, while mice exposed to bisphenols passed on reproductive effects to offspring, when the exposures stopped, the effects disappeared after several generations.
“If we stop poisoning ourselves, we can turn this around,” said Dr. Swan. “That’s what I want people to know.”
Count Down frames the issues in language that is much starker than typically found in academic publications. But that is what’s necessary to draw attention to the effects of chemical exposures on human health and reproduction, Dr. Swan said. “I’m saying this in fairly extreme terms to alarm people, to make them realize it is a crisis and they have to act.”
No disclosures were reported.