Air pollution linked to higher risk of infertility in men

A study in Denmark has found that exposure to PM_2.5  is linked to an increased risk of infertility in men, while road traffic noise was similarly linked to infertility in women over 35.

The cohort for the study was made up of 900,000 men and women aged between 30 and 45, with fewer than two children, cohabiting or married, living in Denmark between 2000 and 2017.

Having access to the historic addresses of participants – including which floor of a building they lived on – the team could estimate levels of PM 2.5 and traffic noise over a period of time that averaged out at just over four years. Because both air and noise pollution can be associated with traffic, the researchers combined exposure models with high quality data to make their exposure estimates.

People with infertility were found through the Danish National Patient Register, meaning that only couples actively seeking infertility counselling were identified as infertile participants in the study.

From 526,056 men, 16,172 were diagnosed with infertility, while 22,672 (out of 377,850 ) women were similarly diagnosed.

After adjusting for factors such as income, education level, and occupation, it was fund that exposure to 2.9 µg/m3 higher average levels of PM2.5 over five years was associated with a 24% increased risk of infertility in men aged between 30 and 45.

Exposure to 10.2 decibel higher average levels of road traffic noise over five years was associated with a 14% increased risk of infertility among women older than 35 years. Noise was not associated with infertility among younger women and PM2.5 was not associated with infertility in women at all.

For men over 37, noise pollution seems to be linked with a small increased risk of infertility.

The researchers speculated on why men seem to be more affected by air pollution than women with regards to fertility: ‘A potential explanation  is that while female follicle development begins in utero, new sperm cells are produced continuously in the testis (after puberty), with an overall lifespan of three months. Therefore, particulate air pollution may act directly on the sperm cells during the vulnerable spermatogenesis phase.’

They conclude: ‘As many western countries are facing declining birth rates and increasing maternal age at the birth of a first child, knowledge on environmental pollutants affecting fertility is crucial. 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.’