Wildfire Smoke Exposure May Reduce Male Fertility, Study Finds

As wildfires become more frequent across the United States and Canada, new research suggests that exposure to wildfire smoke could negatively impact male reproductive health. A recent study conducted by UW Medicine has revealed that wildfire smoke exposure may decrease important sperm parameters in men undergoing fertility treatments.

Published in the journal Fertility and Sterility, the study analyzed semen samples from 84 men who provided sperm for intrauterine insemination procedures between 2018 and 2022. The Seattle area experienced significant wildfire smoke events in 2018, 2020, and 2022. By comparing sperm quality before and during these wildfire seasons, researchers observed notable declines in several key measures of sperm health.

Specifically, during wildfire smoke exposure, men showed reduced sperm concentration, total sperm count, and counts of motile and progressively motile sperm. Interestingly, the percentage of progressively motile sperm slightly increased, but this did not offset the overall decline in sperm quality. The study was designed as a retrospective analysis, with subjects serving as their own controls across different wildfire years, confirming consistent results.

Dr. Tristan Nicholson, the senior author and an assistant professor of urology at UW Medicine, explained that this natural experiment highlights how environmental factors like wildfire smoke can impair reproductive functions. The findings align with previous smaller studies linking air pollution to reproductive health problems, emphasizing the importance of further investigation.

While wildfire smoke particles are known to cause respiratory, cardiovascular, and neurological issues, their impact on male fertility remains less understood. The current research underscores the need to explore how wildfire smoke affects reproductive health across different populations, including women and men of reproductive age.

Although the study did not assess direct reproductive outcomes such as pregnancy or live birth rates, initial data suggest that pregnancy rates among women with partners in the study were around 11%, with live birth rates near 9%, consistent with typical rates. Researchers are now conducting ongoing studies to understand if sperm counts recover after smoke exposure and how long this process might take.

As wildfires intensify, understanding how smoke affects reproductive health becomes increasingly critical. This research highlights the potential fertility risks associated with wildfire smoke and calls for heightened awareness and further scientific exploration to better understand and mitigate these environmental impacts.

Source: https://medicalxpress.com/news/2025-10-wildfire-exposure-linked-sperm-quality.html