Chemicals that pervade our modern world – plastics, pesticides, stain repellents, components of personal hygiene products – are contributing to a decades-long decline in fertility and could pose health risks even into future generations, according to an explosive new book by Shanna Swan, PhD, an environmental and reproductive epidemiologist at the Icahn School of Medicine at Mount Sinai, New York.
Dr. Shanna Swan
Dr. Swan laid out the case that endocrine-disrupting chemicals (EDCs) such as phthalates and bisphenol A (BPA) threaten human existence, a conclusion that stems in part from her 2017 meta-analysis that showed a 52% drop in sperm counts from 1973 to 2011 in men in North America, Europe, and Australia.
“This alarming rate of decline could mean the human race will be unable to reproduce itself if the trend continues,” Dr. Swan said in her book, “Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race,” (New York: Scribner, 2021) coauthored with health journalist Stacey Colino.
Her premise that EDCs pose a risk to both male and female fertility is underscored by new research. A March 2021 article in Human Reproduction links prenatal chemical exposures to lowered fertility in a study of 1,045 Swiss military conscripts.
The Swiss men, aged 18-22 years, were significantly more likely to have low semen volume and low total sperm count if their mothers reported that they had occupational exposures to four or more endocrine-disrupting chemicals while they were pregnant. These EDCs, which mimic natural hormones, included pesticides, heavy metals, phthalates, alkylphenolic compounds, and solvents that can be found in agricultural work or hair and beauty salons.
These chemicals are not so-called “forever chemicals” that persist in the human body. But the Swiss study still showed an association between exposure during pregnancy and the future fertility of the male children. “Those apparently small exposures that pass quickly can affect development,” said Dr. Swan, who was not affiliated with the research. “It takes very little in terms of time and amount of chemicals to alter fetal development.”
Health risks beyond reproduction
While Count Down is placing a new spotlight on chemical hazards, some major medical organizations have already taken positions on the risks. “Reducing exposure to toxic environmental agents is a critical area of intervention for ob.gyns.,” the American College of Obstetricians and Gynecologists said in an environmental policy priority. “The Endocrine Society is concerned that human health is at risk because the current extensive scientific knowledge on EDCs and their health effects is not effectively translated to regulatory policies that fully protect populations from EDC exposures.”
But for the medical community, addressing the impact of EDCs goes beyond advocacy for regulatory and legislative changes, Dr. Swan said in an interview. Physicians should talk to patients about the importance of reducing their chemical exposure to safeguard their overall health.
“Reproductive health and particularly sperm count, subfertility, and infertility are predictors of lifelong health,” she said. That includes associations between reproductive disorders and “the risk of heart disease, obesity, reproductive cancers and, perhaps most dramatically, with a shortened lifespan.”
Dr. Tracey Woodruff
Some medical schools are including information on environmental health and exposure risks in the curriculum, said Tracey Woodruff, PhD, MPH, director of the program on reproductive health and the environment at the University of California, San Francisco. She urged physicians to ask patients about potential occupational exposures to hazardous chemicals and provide information about ways to reduce everyday exposures.
For example, safer options include buying organic produce, microwaving food in glass rather than plastic containers and avoiding products that contain phthalate or BPA. “If you’re going to talk to people about what they eat, that’s a perfect venue for talking about the environment,” said Dr. Woodruff, who coedited the textbook, Environmental Impacts on Reproductive Health and Fertility (Cambridge University Press: Cambridge, England, 2010).
The UCSF program provides patient guides in English and Spanish with suggestions of ways to reduce chemical exposures at work and at home.