Exposure to common air pollutants could change how genes function in sperm, potentially affecting male fertility, pregnancy outcomes and the health of future children according to new research.
The study, which was presented at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE), found that men exposed to mixtures of air pollution during sperm development showed chemical modifications to their sperm DNA that could influence gene activity .
Researchers analysed data from more than 2,000 men in Salt Lake City, Utah, between 2013 and 2017. Participants provided semen samples at enrolment and after 2, 4 and 6 months, with sperm DNA methylation analysed in the 1,220 men who completed the six-month follow-up .
The team estimated each participant’s exposure to outdoor pollutants including ozone, nitrogen dioxide, sulphur dioxide and PM2.5 during spermatogenesis – the approximately three-month process of sperm production.
Researchers identified 39 DNA methylation changes associated with air pollution mixtures, with ozone and nitrogen dioxide emerging as the strongest contributors. Methylation involves chemical modifications that regulate gene activity without altering the underlying DNA itself.
Among the most notable findings was that pollution affected a gene called GNAS, which is known to be linked to poorer sperm quality and is also important for the healthy development of babies in the womb.
While previous studies have linked air pollution to poorer semen quality, far less has been known about how these exposures may influence sperm at the molecular level. The new findings raise questions about male fertility, pregnancy outcomes and the long-term health of offspring.
Lead author Dr Carrie Nobles said: ‘Our findings suggest that air pollution exposure during key stages of sperm development may be associated with changes in sperm DNA methylation, including in genes involved in spermatogenesis and early developmental processes.
‘The association with changes in the imprinted gene GNAS was particularly important. Because imprinted genes can persist through early embryonic development, this raises important questions about whether fathers’ environmental exposures may influence not only fertility, but pregnancy and offspring health.
‘A critical next step is replication of findings in other studies. We also need to understand whether air pollution-associated changes in sperm DNA methylation have measurable downstream impacts on men’s fertility and couples’ pregnancy health. Future research should also explore the role of indoor and personal air pollution exposure.’
Professor Dr Karen Sermon, Immediate Past Chair of ESHRE, commented: ‘This is another piece of the puzzle to understand how pollution negatively influences our fertility. We know that couples exposed to air pollution often have difficulties becoming pregnant, and this may be one of the explanations amongst the myriad ways that pollution impacts our reproductive health.’
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