Air pollution linked to a higher risk of infertility in men

Long-term exposure to fine particulate air pollution (PM2.5) is linked to a higher risk of infertility in men, while road traffic noise is linked to a higher risk of infertility in women over 35, according to a Danish study published by The BMJ.

If these findings are confirmed in future studies, they could help guide strategies to regulate noise and air pollution to protect the general population from this exposure, the researchers say.

Infertility is a major global health problem that affects one in seven couples trying to conceive.

Several studies have found a negative association between particulate air pollution and sperm quality and success after fertility treatment, but results on fertility (the likelihood of becoming pregnant) are inconsistent and no studies have examined the effects of transport noise on infertility in men and women.

To address this uncertainty, researchers set out to investigate whether long-term exposure to road traffic noise and particulate matter (PM2.5) air pollution was associated with a higher risk of infertility in men and women.

Their findings are based on national registry data from 526,056 men and 377,850 women aged 30 to 45, with fewer than two children, cohabiting or married, and living in Denmark between 2000 and 2017.

This group was selected to include a large proportion of people who are actively trying to conceive and therefore at risk of an infertility diagnosis. Individuals with an existing diagnosis of infertility were excluded, as were women who had undergone surgery that prevented pregnancy and men who had been sterilized.

Annual average PM2.5 concentrations and road traffic noise levels at each participant’s address (1995–2017) were calculated, and diagnoses of infertility were recorded from the National Patient Register.

Infertility was diagnosed in 16,172 men and 22,672 women during an 18-year follow-up period (average just over 4 years).

After adjusting for several potentially influential factors, including income, education level and occupation, the exposure is 2.9 µg/m³ higher five-year average levels of PM2.5 were associated with a 24% increased risk of infertility in men aged 30-45. PM2.5 was not associated with infertility in women.

Exposure to 10.2 decibels higher average levels of road traffic noise over five years was associated with a 14% increased risk of infertility in women over 35 years of age. Noise was not associated with infertility in younger women (30-35 years).

In men, traffic noise was associated with a small increased risk of infertility in the 37-45 age group, but not among the 30-37 age group.

The higher risk of noise-related infertility in women and PM2.5-related infertility in men was consistent among people living in rural, suburban and urban areas, as well as among people of low, medium and high socio-economic status.

This is an observational study, so no cause can be determined, and the researchers acknowledge that couples who were not trying to conceive may have been included, and that information on lifestyle factors and exposure to noise and air pollution at work and during leisure activities was missing. .

However, this was a large study, based on reliable health and housing data, using validated models to assess pollution and noise levels, and allowed the researchers to take into account a range of important social and economic factors.

As such, they conclude: “If our results are confirmed in future studies, it suggests that the political implementation of air pollution and noise control could be important tools to improve birth rates in the Western world.”