Air pollution is associated with a higher infertility risk in men, while noise pollution is associated with a higher risk of infertility in women, a study has found.
The study, which has been peer-reviewed and published in the BMJ, looked at whether long-term exposure to road traffic noise and fine particulate matter (PM2.5), a particular form of air pollution, was associated with a higher risk of infertility in men and women.
It drew from a database of 526,056 men and 377,850 women aged 30 to 45 who had fewer than two children, were cohabiting or married, and who had lived in Denmark between 2000 and 2017. This subset of the database was selected to include a high proportion of people who were actively trying to become pregnant.
The study excluded sterilised men and women who had had surgery to prevent pregnancy.
Between 1995 and 2017, the average amount of PM2.5 pollution was recorded at the addresses of each participant, and infertility diagnoses were recorded from the national patient register.
Across the 18-year period, infertility was diagnosed in 16,172 men and 22,672 women, and after adjusting for factors such as income, education level and occupation, it was found that exposure to levels of PM2.5 that were 2.9 micrograms per cubic metre higher than average over five years was associated with a 24% increased risk of infertility in men aged 30 to 45.
Although PM2.5 was not associated with infertility in women, exposure to levels of road traffic noise that were 10.2 decibels higher than average over five years was associated with a 14% increased risk of infertility among women over 35, while for women aged between 30 and 35 noise was not associated with infertility.
Road traffic noise was associated with a small increased risk of male infertility for those aged between 37 and 45, but not those aged between 30 and 37.
Infertility affects one in seven couples in the UK trying to conceive.
The researchers said several previous studies had found negative links between particulate air pollution and sperm quality, but t these studies had been inconsistent.
They concluded: “Based on a nationwide cohort, designed to include a high proportion of people actively trying to achieve pregnancy, we found that PM2.5 was associated with a higher risk of an infertility diagnosis among men and road traffic noise was associated with a higher risk of an infertility diagnosis among women older than 35 years, and possibly among men older than 37 years.
“As many western countries are facing declining birthrates 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 birthrates in the western world.”