The study, conducted by Danish scientists and published in The BMJ, reveals major findings regarding the effects of PM2.5 particles and road traffic noise on reproductive health.
The research involved over 500,000 men and nearly 400,000 women aged between 30 and 45 who were living in Denmark with a partner between 2000 and 2017.
The participants included a high proportion of people actively trying to conceive, excluding those with pre-existing infertility diagnoses or those who had undergone sterilization procedures.
The researchers calculated the yearly average PM2.5 concentration and road traffic noise level at the address of every participant between 1995 and 2017 and compared this data to the success of conception.
The study found that long-term exposure to PM2.5, which are pollution particles smaller than 2.5 micrometres, was linked to a 24% increased risk of infertility in men.
These particles can originate from road traffic, including carbon emissions from engines, small bits of metal and rubber from engine wear and braking, as well as dust from road surfaces. They can also come from building materials, industry, wind-blown dust, sea salt, pollens, and soil particles.
Professor Jill Belch, an expert in vascular medicine and air pollution from the University of Dundee, commented on the study, stating, "This is a key study linking even more toxic effects to exposure to air pollution in particular to the very small particles PM2.5."
Interestingly, the study did not find an association between PM2.5 and infertility in women. However, it did reveal that exposure to higher average levels of road traffic noise over five years was linked to a 14% increased risk of infertility among women over 35 years old.
The researchers suggested that stress and sleep disturbances caused by noise pollution might impair reproductive function, including reduced sperm count and quality, and menstrual irregularity. The findings were consistent for participants living in both rural and urban areas, regardless of their financial status.
Professor Allan Pacey, an expert in andrology at the University of Manchester, noted that while the study was good, its findings were limited. He stated, "It is possible that the real cause of this association lies with something that it was not possible to measure."
Additionally, the authors acknowledged that they did not have information on lifestyle factors such as alcohol use, smoking, or body mass index, which could also influence fertility outcomes.
Despite these limitations, the study's implications are profound. If replicated, the findings could help create strategies and policies to protect the population from the adverse effects of noise and air pollution on reproductive health. As Professor Belch emphasized, "More attention needs to be paid to achieving legal limits of air pollution by Government and Local Authorities."
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