AIR POLLUTION DAMAGES DNA IN SPERM, STUDY SUGGESTS
Air pollution may switch off genes that make healthy sperm, scientists have discovered.
Previous studies have shown that men living in polluted areas had poorer sperm quality and higher levels of infertility, but it was unknown what was driving the effect.
US researchers have now shown that breathing in dirty air appears to affect genes thought to be responsible for sperm development and cell quality.
Sperm takes around three months to develop and researchers discovered that men exposed to air pollution during that period had worrying chemical tags added to the DNA of important genes.
The addition of these tags – known as DNA methylation – acts like a dimmer switch or a piece of tape over a light switch. Although it does not change the underlying code, it can stop genes being read successfully.
Dr Carrie Nobles, lead author of the University of Massachusetts, 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.
“We need to understand whether air pollution-associated changes in sperm DNA have measurable downstream impacts on men’s fertility and couples’ pregnancy health.”
Sperm counts have been declining globally for the past 50 years, dropping more than 50 per cent since the 1970s. Scientists have been trying to find the reasons and chemicals in the environment are among the chief suspects, but there has been little definitive evidence.
Allan Pacey, professor of andrology at the University of Manchester, added: “There has been growing evidence in recent years that aspects of human health can be impacted by air pollution, and this includes male infertility.
“However, we have not really understood much about the likely mechanism by which this occurs.
“Whether the observed changes to sperm DNA methylation are clinically meaningful for male infertility and further work will need to be done to confirm or refute that.”
For the latest study, scientists took semen samples from more than 2,000 men during a six-month period and then studied sperm DNA methylation after the final visit.
They also measured their exposure to air pollutants including ozone, nitrogen dioxide, sulphur dioxide and fine particulate matter.
‘Growing body of evidence’
Researchers identified 39 DNA changes associated with air pollution mixtures, with ozone and nitrogen dioxide emerging as the strongest culprits.
British experts said the findings were important and called for more studies to look at the link between DNA damage and air pollution.
Richard Lea, professor of reproductive biology at the University of Nottingham, said: “This is an important piece of research that adds to a growing body of evidence that sperm quality is adversely affected by airborne pollutants.
“Since there is currently increased public, academic and clinical awareness around pollutant effects on reproductive health, the release of this work in abstract form is timely.
“Although air pollution is recognised as a major route of exposure with studies beginning to emerge in the literature, few studies have directly addressed this by identification of differentially methylated genes in sperm.”
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The research was published in the journal Human Reproduction and presented at the annual meeting of the European Society of Human Reproduction and Embryology.
Prof Karen Sermon, a former chairman of the society, said: “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 among the myriad ways that pollution impacts our reproductive health.”
2026-07-07T06:05:15Z
