A major fertility study presented this week at the European Society of Human Reproduction and Embryology annual meeting in London found associations between air pollution exposure and epigenetic changes in sperm DNA. Researchers tracked more than 2,000 men in Salt Lake City, Utah over several years, collecting semen samples at multiple time points and estimating their exposure to outdoor air pollutants during the three-month sperm development window preceding each sample collection.
The investigation focused on DNA methylation, chemical modifications attached to DNA that control whether genes are activated or deactivated without altering the underlying genetic sequence. Among the 1,220 participants who provided samples at the six-month mark, scientists identified 39 DNA changes associated with air pollution mixtures. Ozone and nitrogen dioxide emerged as the pollutants showing the strongest connection to these epigenetic modifications, with sulphur dioxide and fine particulate matter also examined.
While previous research has suggested air pollution may reduce male fertility, the biological mechanisms have remained unclear. The findings point to DNA methylation as a potential explanatory pathway. Notably, one identified gene called GNAS has previously been associated with reduced semen quality and problems in fetal development. Most epigenetic markers are typically erased early in embryo development, though certain imprinted genes retain these changes with potential effects on developmental processes.
Lead researcher Dr. Carrie Nobles of the University of Massachusetts Amherst emphasized that exposure during critical stages of sperm development may drive these DNA changes. However, independent experts cautioned that further investigation is necessary to establish clinical significance. Prof. Allan Pacey of the University of Manchester noted the study demonstrated measurable effects but stressed that determining whether the observed methylation changes meaningfully impact male infertility requires additional research.
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