A recent Danish study published by The BMJ revealed a concerning link between long-term exposure to fine particulate matter (PM2.5) air pollution and a higher risk of infertility in men.
Additionally, the study found that road traffic noise is associated with a greater risk of infertility in women over 35. These findings, if supported by future research, could play a crucial role in shaping regulations to mitigate the impact of noise and air pollution on the general population. Infertility affects a significant portion of couples worldwide, with an estimated one in seven couples struggling to conceive.
Numerous studies have uncovered concerning connections between particulate air pollution and sperm quality, as well as the success of fertility treatments. However, the impact on the likelihood of conceiving, known as fecundability, remains inconsistent. Additionally, little research has delved into the effects of transport noise on infertility in both men and women.
In response to this uncertainty, a team of researchers embarked on a study to explore whether prolonged exposure to road traffic noise and fine particulate matter (PM2.5) air pollution correlated with an increased risk of infertility in both men and women.
Their findings draw from national registry data for 526,056 men and 377,850 women aged 30-45 years, each with fewer than two children, cohabiting or married, and living in Denmark between 2000 and 2017.
The study carefully selected participants actively trying to conceive, making them more likely to be at risk of infertility. Those who already had infertility diagnoses and individuals who had undergone procedures preventing pregnancy were excluded from the study.
The researchers calculated yearly average PM2.5 concentrations and road traffic noise levels at each participant’s address from 1995 to 2017 and recorded infertility diagnoses from the national patient register. The study found that 16,172 men and 22,672 women were diagnosed with infertility during the 18-year follow-up period, with an average duration of just over four years.
After controlling for various influential factors such as income, education, and occupation, it was found that exposure to higher levels of PM2.5 over five years led to a 24% increased risk of infertility in men aged 30-45. Interestingly, PM2.5 was not associated with infertility in women.
Similarly, a 10.2-decibel increase in average road traffic noise over five years was linked to a 14% higher risk of infertility in women over 35. Notably, there was no association between noise and infertility in women aged 30-35.
Moreover, in men, road traffic noise was found to be associated with a slightly higher risk of infertility in the 37-45 age group but not among those aged 30-37.
The study found that the risk of noise-related infertility in women and PM2.5-related infertility in men was consistently higher across different living environments and socioeconomic statuses. Although this is an observational study and cannot prove cause and effect, the large sample size and use of reliable health and residential data, along with validated models to assess pollution and noise levels, make the findings significant.
It is important to note that the study lacked information on lifestyle factors and exposure to noise and air pollution at work and during leisure activities, and couples not trying to conceive may have been included. Despite these limitations, the researchers were able to account for a range of important social and economic factors.
As such, they conclude: “If our results are confirmed in future studies, it suggests that political implementation of air pollution and noise mitigations may be important tools for improving birth rates in the Western world.”
Journal reference:
- Mette Sørensen, Aslak Harbo Poulsen, Bugge Nøhr, Jibran Khan, Matthias Ketzel, Jørgen Brandt, Ole Raaschou-Nielsen, Allan Jensen. Long-term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study. BMJ 2024; DOI: 10.1136/bmj-2024-080664