Air Pollution Alters Sperm Gene Function
Research involving over 2,000 men has revealed that exposure to common outdoor air pollutants may induce subtle changes in sperm DNA, potentially affecting gene activity. This large-scale fertility study highlights concerns about the impact of air pollution on male reproductive health.
The findings were presented on Tuesday at the annual meeting of the European Society of Human Reproduction and Embryology held in London. The study identified ozone and nitrogen dioxide as the pollutants most strongly associated with epigenetic modifications in sperm.
“Our findings suggest that air pollution exposure during key stages of sperm development may be associated with changes in sperm DNA.”
Dr Carrie Nobles, an epidemiologist at the University of Massachusetts Amherst and lead author of the study, emphasized the significance of these results.
Study Design and Methodology
The research tracked more than 2,000 men residing in Salt Lake City, Utah, from 2013 to 2017. Participants provided semen samples at enrollment and subsequently after two, four, and six months.
Researchers estimated each participant’s exposure to outdoor air pollutants—including ozone, nitrogen dioxide, sulphur dioxide, and fine particulate matter—during the three months preceding each semen sample collection. This timeframe corresponds to the period of sperm production.
Epigenetic Mechanisms and Findings
While growing evidence has linked air pollution to male fertility issues, the underlying biological mechanisms have remained unclear. This study suggests DNA methylation as a potential mechanism. DNA methylation involves chemical tags attached to DNA that regulate gene expression without altering the genetic code itself.
Scientists analyzed sperm DNA methylation patterns in 1,220 men who provided samples at the six-month follow-up. They identified 39 DNA methylation changes associated with exposure to air pollution mixtures. Among these, ozone and nitrogen dioxide showed a particularly strong influence.
Although most epigenetic tags are erased early in embryo development, some genes retain these modifications through imprinting. Such imprinted genes can influence embryo development and subsequent health outcomes. One gene identified in this study, GNAS, has been previously linked to reduced semen quality and fetal development issues.
“Changes in gene expression have the potential to impact men’s fertility, which is why this area of research is important. Future work is needed to make a direct link between air pollution-associated changes in sperm DNA methylation and fertility.”
Dr Nobles highlighted the importance of further research to establish a direct causal relationship between these epigenetic changes and fertility outcomes.
Expert Commentary
Professor Allan Pacey, a professor of andrology at the University of Manchester who was not involved in the study, acknowledged the measurable effect demonstrated by the research.
“At the present time, it is not possible to conclude 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.”
Professor Richard Lea, a professor of reproductive biology at the University of Nottingham, also commented on the study’s contribution.
“This is an important piece of research that adds to a growing body of evidence that sperm quality is adversely affected by airborne pollutants.”
