Long-term exposure to air pollution may increase infertility risk in men

Key takeaways:

• Long-term exposure to particulate matter in the air was linked to infertility in men.
• Noise pollution from road traffic was linked to infertility in certain women.

Exposure to air pollution over a half-decade increased the risk for infertility in men, the results of a nationwide cohort study published in BMJ showed.

Results from the analysis also revealed a link between noise pollution from road traffic and infertility among women aged 35 to 45 years, researchers noted.

According to background information from WHO, around 17.5% of adults — or one in six — experience infertility worldwide.

“It is really interesting that for both noise and air pollution, we [found that] the increase in risk follows a linear association with no ‘safe’ lower threshold,” Mette Sørensen, PhD, an associate professor of epidemiology from the Danish Cancer Institute in Denmark, told Healio.

Sørensen and colleagues pointed out that air pollution has been negatively tied to sperm quality and reduced success rates after infertility treatment in women, “although results are inconsistent,” they wrote.

In the study, the researchers used Danish National Patient Register data to assess the impact of road traffic noise and fine particulate matter (PM^2.5) on infertility in men and women aged 30 to 45 years who had fewer than two children, were married or cohabited and who resided in Denmark between 2000 to 2017.

Most of the people in the sample were actively trying to become pregnant, putting them at risk for a diagnosis of infertility, Sørensen and colleagues noted, while individuals with an existing infertility diagnosis were excluded from the study.

Overall, the analysis included 526,056 men and 377,850 women.

A total of 16,172 men and 22,672 women had a diagnosis of infertility during an 18-year follow-up period.

The researchers found an association between exposure to 2.9 µg/m³ higher average levels of PM^2.5 over a period of 5 years and a 24% increased risk for infertility among men aged 30 to 36 years (HR = 1.24; 95% CI, 1.18-1.3) and those aged 37 to 45 years (HR = 1.24; 95% CI, 1.15-1.33).

They did not report any association between exposure to particulate matter and infertility in women.

Meanwhile, the analysis linked exposure to 10.2 decibel higher average levels of road traffic noise over 5 years to a 14% increased risk for infertility in women aged 35 to 45 years (HR = 1.14; 95% CI, 1.1 to 1.18).

Women aged 30 to 34 years did not have an increased risk.

Long-term exposure to road traffic noise also increased the risk for infertility in men aged 37 to 45 years (HR = 1.06; 95% CI, 1.02-1.11), but this increase was not seen in men aged 30 to 36 years.

The higher risks for infertility in men and women tied to PM^2.5 and road traffic noise, respectively, were consistent across people living in rural, suburban and urban areas and across socioeconomic status levels.

“Particulate air pollution may act directly on the sperm cells during the vulnerable spermatogenesis phase,” Sørensen and colleagues wrote, which could explain why infertility in women was not impacted by PM^2.5.

Researchers identified several study limitations. The researchers did not have access to data on lifestyle factors like smoking and BMI.

They also had a lack of information on PM^2.5 and road traffic noise levels at places like work.

Sørensen and colleagues pointed out that understanding environmental impacts has become crucial as many countries face decreasing birth rates.

Regarding future research, “we would like to investigate whether air pollution and noise exposure has any effect on the success of fertility treatment (whether you achieve pregnancy or not),” Sørensen told Healio.

References:

• Air pollution linked to higher risk of infertility in men. Available at: https://www.eurekalert.org/news-releases/1056542. Published Sept. 4, 2024. Accessed Sept. 4, 2024.
• Sørensen M, et al. BMJ. 2024;doi:10.1136/ bmj-2024-080664.
• 1 in 6 people globally affected by infertility: WHO. Available at: https://www.who.int/news/item/04-04-2023-1-in-6-people-globally-affected-by-infertility. Published April 4, 2023. Accessed Sept. 4, 2024.