As wildfires become more common across the United States, a new study suggests that the increased exposure to smoke may make it harder for some couples to conceive.
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That’s because wildfire smoke may compromise sperm quality in men undergoing fertility treatments, according to the study.
“As we see more frequent and intense wildfire events, understanding how smoke exposure impacts reproductive health is critical,” senior author Tristan Nicholson, MD, PhD, an assistant professor of urology at the University of Washington School of Medicine and a reproductive urologist at the UW Medicine’s Men’s Health Center, said in a statement.
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For the study, researchers examined semen samples from 84 men in the Seattle area who provided sperm for intrauterine insemination (IUI) procedures between 2018 and 2022. IUI, also called artificial insemination, is a fertility procedure where specially prepared sperm is placed directly in a woman’s uterus while she’s ovulating, with the goal of increasing the chance of pregnancy.
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All of the study participants provided semen samples before and after exposure to wildfire smoke. There were major fires in the Seattle area in 2018, 2020, and 2022.
Sperm Quality Declined After Wildfires
Sperm samples collected after the wildfires were significantly poorer in quality than samples taken before exposure, according to findings published in the journal Fertility and Sterility.
Wildfire exposure was associated with:
- Declines in total sperm count, or the total amount of sperm released during ejaculation
- Decreased total sperm concentration, or how much sperm is in a milliliter of semen
- Reductions in total progressively motile sperm count, or the proportion of sperm ejaculated that can swim forward effectively enough to potentially reach and fertilize an egg
The study wasn’t designed to prove whether or how wildfire smoke exposure might directly impact sperm quality, fertility, or pregnancy outcomes. It’s also unclear whether sperm quality would be permanently altered by smoke exposure, or if it would potentially recover to its pre-exposure quality over time.
How Wildfire Smoke Might Damage Sperm
Inhaling tiny particles in wildfire smoke might compromise sperm quality because it leads to systemic inflammation, interferes with hormones that play a role in reproduction, or interferes with the quality of DNA, says Elizabeth Rubin, MD, an assistant professor of obstetrics and gynecology at Oregon Health & Science University in Portland, who has studied the impact of smoke exposure on fertility.
“In any of these situations, the result is that the body is less able to make high-quality sperm,” says Dr. Rubin, who wasn’t involved in the new study. “Lower quality or quantity of sperm may make getting pregnant or staying pregnant harder, or even impact developing embryos for patients undergoing in vitro fertilization.”
The male body produces sperm continuously, so it’s possible that sperm quality damaged by wildfire exposure may improve over time, Rubin says.
However, it’s also possible that repeated exposure to wildfires might cause cumulative damage to the body’s ability to produce sperm, Rubin adds.
“Unfortunately, there are many things we don’t know about the impact of wildfire smoke on fertility, including the impacts to sperm,” Rubin says. “More long-term studies are needed, particularly in people who are repeatedly exposed, such as wildfire fighters.”
Taking Precautions During Wildfires
“Anyone living in an area being impacted by wildfire smoke should take steps to decrease their risks, not only in terms of fertility but also for lung health,” Rubin says.
To reduce your smoke exposure, Rubin recommends:
- Wearing a mask
- Staying indoors
- Using air filters when possible
Even just avoiding doing things like yard work, mowing, or cleaning outdoors during smoky periods will help.
“None of these have been studied in the context of fertility, and it can be hard to know exactly how much benefit each option gives you, but all are helpful for your overall health,” Rubin says.
