Air Pollution Linked to Changes in Male Fertility and Offspring Health

A recent study has revealed that the effects of air pollution extend beyond respiratory and cardiovascular systems, potentially impacting male reproductive health as well.

Researchers identified that men exposed to higher levels of air pollutants during sperm development exhibited alterations in a process known as DNA methylation. This chemical modification regulates gene activity without altering the DNA sequence itself.

The investigation involved over 2,000 men from Salt Lake City, Utah, between 2013 and 2017. Participants provided semen samples at the study's outset and again after two, four, and six months. The researchers analyzed samples from 1,220 men during the final follow-up to detect changes in sperm DNA methylation.

Exposure to various air pollutants was measured during the approximately three-month period of sperm formation. These pollutants included ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide, and fine particulate matter (PM2.5).

The research team identified 39 DNA methylation changes associated with exposure to a combination of these pollutants. Ozone and nitrogen dioxide showed the strongest correlations with these alterations. Notably, changes were observed in the GNAS gene, an imprinted gene previously linked to reduced semen quality and involved in embryonic development. (An imprinted gene is subject to chemical marks that determine which parental copy is active or inactive depending on inheritance from the mother or father.)

Dr. Carrie Nobles, the study’s lead author, stated that the findings suggest exposure to air pollution during sperm development may be linked to genetic changes involved in sperm formation and early developmental processes.

She emphasized the significance of the association with the GNAS gene, explaining that imprinted genes can remain active during early embryonic growth. This raises questions about whether paternal environmental exposures might influence fertility and offspring health.

Air pollution is recognized as a growing global health risk, with previous studies linking it to cardiovascular and respiratory diseases as well as decreased semen quality. However, the molecular mechanisms by which these pollutants affect sperm remain incompletely understood.

Nobles noted that air pollution is a complex mixture of contaminants varying by location and season. She highlighted that levels of certain pollutants, such as nitrogen dioxide and ozone, tend to be higher in urban areas due to vehicle emissions and natural gas combustion.

The researcher confirmed that the next step involves replicating these findings in other studies and determining whether the DNA methylation changes in sperm caused by air pollution exposure lead to measurable effects on male fertility or pregnancy outcomes.

The study’s results were presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) and published in the journal Human Reproduction.