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A Danish study looked at more than 16,000 men and 22,000 women, and found that exposure to air and noise pollution correlated with a increased risk of male infertility. However, it is worth noting that while the authors suggest possible reasons that this may be the case, the study does not attempt to prove a causal link.
Professor Debbi Stanistreet, Head of the Department of Public Health and Epidemiology at the Royal College of Surgeons in Ireland, said:
“Whilst more and more evidence is coming to light on the impact of air pollution on health, fertility is an area in which relatively little research has been undertaken.
This study is a cohort design which follows a population over time, and therefore is considered a fairly strong research design when considering whether exposure to air pollution leads to a specific health outcome, in this case infertility
The study found a significant relationship between exposure to air pollution and an increased risk of an infertility in men. It also found that road traffic noise was associated with a higher risk of an infertility among women older than 35 years.
As few studies have been carried out in this area, similar studies are now required to see whether the results are replicated among other populations.
If results are found to be consistent across different populations and using different methods of measuring fertility and air pollution, this will strengthen the evidence of a causal relationship between air pollution and infertility.
Given that such a high proportion of the population are exposed to worrying levels of air pollution, it is an important area of concern and action in relation to global health, especially as exposure is already known to be associated with many serious health problems.
It is also worth noting that a very significant amount of exposure to PM2.5 in Ireland, is associated with home heating stoves that burn wood, peat and other forms of biomass. Thus, if the findings are proved to be found to be repeated across other populations, the risk could potentially also be found in rural areas where many people have heating stoves in their homes, not just in areas with high levels of pollution from traffic.”
‘Long term exposure to road traffic noise and air pollution and risk of infertility in men and women: nationwide Danish cohort study’ by Allan Jensen et al. was published in The BMJ at 23:30 UK time Wednesday 4 September 2024.
DOI: 10.1136/bmj-2024-080664
VIA UK SMC
Professor Jill Belch, an expert in vascular medicine and air pollution from the University of Dundee’s School of Medicine, said:
“This is a key study linking even more toxic effects to exposure to air pollution in particular to the very small particles PM2.5.
“Childlessness can be catastrophic for some, and it is likely that the known harmful effects on sperm quality and movement are at play here. More attention needs to be paid to achieving legal limits of air pollution by Government and Local Authorities.
“Noise pollution does not get enough attention in terms of amelioration, we know it has effects on mental health, hearing and sleep – even when asleep noise is perceived as a danger signal causing the ‘fight or flight’ response to occur resulting in poor sleep quality. The mechanism of decreased fertility in women could be related to these, or to a completely unknown mechanism, but the implications of this study, if validated, should require a soundproofing standard for all new builds.
“This is an observational study and these are subject to some scientific constraints by their very nature. However, this was a large well-constructed study taking into account confounders. If validated by future prospective work then this association has striking implications for fertility as a 24% fall in male fertility and a 14% in female fertility would have very profound effects on future generations.”
Prof Allan Pacey, Professor of Andrology at the University of Manchester, said:
“This is an elegant study which uses register data in Denmark to assess air pollution, traffic noise and infertility diagnosis. It’s the kind of study that we could only dream of doing in the UK!
“The results are interesting and seem to confirm the hypothesis that exposure to fine particulate matter (PM2.5) air pollution is linked to a higher risk of infertility in men. This has been an area of concern for a while, but my reading of the literature is that the previous studies have been relatively small and frequently used surrogate markers of infertility such as changes to semen quality. In this current study the authors have linked exposure to infertility diagnosis which is more robust in my view.
“I am not able to comment on the observation that traffic noise is somehow associated to the risk of infertility in women. This is not my area of expertise. But in interpreting all of the study findings we should remember that this is an association and from the data presented we cannot infer cause or effect.
“Whilst the authors of the study have done a good job in controlling (adjusting) for several important confounders, such as socioeconomic factors, it is possible that the real cause of this association lies with something that it was not possible to measure. For example, the authors are clear that they did not have information on lifestyle factors, such as alcohol use, smoking, or body mass index.
“However, overall, I think this is a good study and it should serve as useful basis for future investigations in other countries that are able to link their databases like this.”
Professor Alison Campbell, Chief Scientific Officer at Care Fertility & Honorary Professor, University of Kent, said:
“This large observational study involving nearly one million Danish people is a rare and complex undertaking, requiring extensive data collection over many years. While the research is commendable, certain estimations and assumptions were necessary, such as road traffic noise and pollution levels, and the study could not account for environmental exposure outside the home, like in the workplace.
“Although noise has not been widely studied in relation to fertility, there is evidence suggesting a link between noise-induced stress and sleep disturbance, which could impact fertility. Previous studies have already shown air pollution affects sperm quality, though evidence regarding its impact on female fertility is mixed, highlighting the need for further research in this area.
“The study’s findings come amid a decline in birth rates in many countries, over the past decade. Whilst some people elect not to have children for a broad number of reasons, infertility is a health problem that contributes to these statistics. Social, political, and economic factors also influence birth rates and further research into environmental factors like noise and pollution could shed light on new solutions. Despite the scale and construction of this study, its findings need to be confirmed in other populations.
“People trying to conceive should not be unduly concerned by this research and are advised to take proactive, proven steps such as avoiding smoking, limiting alcohol consumption, and maintaining a healthy weight, to support their fertility and consulting a medical specialist for further help and advice.”
Declared interests
Prof Allan Pacey: In the last 2 years I have been in receipt of income from grants, commercial contracts and donations from Cryos International, CytoSwim Ltd, Exceed Health, Mealis Group, Carrot Fertility. But all monies were donated to the University of Sheffield (my former employer) to support research and training. I am also an unpaid trustee of the Progress Educational Trust (Charity Number 1139856), Patron of The Fertility Alliance (Charity Number 1206323), and Chair of the Advisory Committee of the UK NEQAS Reproductive Science EQA Scheme.
Prof Alison Campbell: Alison Campbell is a minor shareholder in Care Fertility.
Prof Jill Belch: all current work is funded by local charities (Miller, TICR, Sir John Fisher, Northwood Trust), so no industry funding.