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• Posted October 9, 2025

Wildfire Smoke Might Damage Male Fertility

Wildfire smoke could be damaging men’s fertility, according to a new study.

Key measures of sperm quality appeared to drop among dozens of men participating in fertility treatments, researchers recently reported in the journal Fertility and Sterility.

“These results reinforce growing evidence that environmental exposures — specifically wildfire smoke — can affect reproductive health,” said senior researcher Dr. Tristan Nicholson, an assistant professor of urology in the University of Washington School of Medicine in Seattle.

“As we see more frequent and intense wildfire events, understanding how smoke exposure impacts reproductive health is critical,” she added in a news release.

For the study, researchers analyzed semen samples from 84 men taken as part of intrauterine insemination procedures in the Seattle area between 2018 and 2022.

Major wildfire smoke events hit Seattle in 2018, 2020 and 2022, researchers noted. The team compared the men’s sperm quality during and between these events.

“This study takes advantage of our institution’s location in the Puget Sound region, where wildfire smoke events create distinct pre- and post-exposure periods in a natural experiment to examine how a sudden, temporary decline in air quality influences semen parameters,” researchers wrote.

Results showed consistent declines in sperm concentration, total sperm count and sperm movement during wildfire smoke exposures.

Wildfire smoke contains particle pollution that can invade a person’s organs through their lungs and bloodstream, researchers said.

This exposure has previously been linked to lung cancer, respiratory disease, heart attack, stroke and mental impairment, but its effect on male fertility has not been well-studied, researchers said.

Overall, the pregnancy rate among the men’s partners was 11%, and the live birth rate 9% — both at the low end of the average range, researchers noted.

However, the team added that the study was not designed to fully evaluate the direct impact of wildfire smoke on reproductive outcomes.

Researchers next plan to see what happens after wildfire smoke has dented a man’s fertility.

“We are very interested in how and when sperm counts recover after wildfire smoke exposure,” Nicholson said. “Currently we are conducting a prospective pilot study of men in the Seattle area to evaluate how wildfire smoke affects sperm quality.”

More information

The U.S. Centers for Disease Control and Prevention has more on wildfire smoke’s effect on human health.

SOURCE: University of Washington, news release, Oct. 1, 2025

• Infertility
• Hormones: Male