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A recent Danish study published in The BMJ has revealed that long-term exposure to fine particulate matter (PM2.5) air pollution is associated with a higher risk of infertility in men. Conversely, road traffic noise appears to be linked to an increased risk of infertility in women over the age of 35. The findings, if confirmed by future research, could inform strategies to regulate both noise and air pollution to protect public health.
Infertility is a significant global health issue, affecting approximately one in seven couples attempting to conceive. While previous studies have explored the impact of particulate air pollution on sperm quality and fertility treatment success, results concerning fecundability— the likelihood of conceiving— have been inconsistent. Additionally, research on the effects of road traffic noise on infertility has been limited.
To address these gaps, researchers analyzed national registry data from Denmark, encompassing 526,056 men and 377,850 women aged 30-45 years, who were cohabiting or married and had fewer than two children. The study period spanned from 2000 to 2017, with a focus on individuals actively trying to conceive. Those with existing infertility diagnoses or undergoing sterilization procedures were excluded from the study.
The researchers calculated yearly average PM2.5 concentrations and road traffic noise levels at participants’ addresses from 1995 to 2017. They then cross-referenced these environmental exposures with infertility diagnoses recorded in the national patient register.
During an 18-year follow-up period, infertility was diagnosed in 16,172 men and 22,672 women. The study found that a 2.9 µg/m³ increase in average PM2.5 levels over five years was associated with a 24% higher risk of infertility in men aged 30-45 years. Interestingly, PM2.5 levels did not appear to affect infertility risk in women.
For women over 35 years old, a 10.2-decibel increase in road traffic noise over five years was linked to a 14% higher risk of infertility. However, this association was not observed in younger women (30-35 years). In men, road traffic noise was associated with a modest increase in infertility risk for those aged 37-45 years, but not for those aged 30-37 years.
The study’s results were consistent across rural, suburban, and urban areas and among individuals with varying socioeconomic statuses. Despite these findings, the study’s observational nature means that causation cannot be definitively established. The researchers acknowledged limitations, including the inclusion of couples not actively trying to conceive and a lack of data on lifestyle factors and exposure to noise and air pollution during work or leisure activities.
Nonetheless, the researchers suggest that if these results are corroborated by future studies, implementing policies to mitigate air pollution and noise could be crucial in improving fertility rates in Western countries.
For further details, see the study published in The BMJ: “Long term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study,” DOI: 10.1136/bmj-2024-080664.
