Air quality is linked to a wide range of health problems, including respiratory diseases, cardiovascular complications, and cancer, and the list is only growing. According to research presented this week at the 42nd annual conference of the European Society of Human Reproduction and Embryology (ESHRE), common pollutants can fundamentally disrupt the genetic makeup of human sperm, and these changes may impact more than just male fertility.
One of the largest studies of its kind, this project was conducted from 2013 to 2017 and involved over 2,000 men in Salt Lake City, Utah. Volunteers provided sperm samples to the researchers, first upon enrollment and then at intervals of two, four, and six months. The researchers focused specifically on studying changes in sperm DNA methylation. These chemical shifts regulate genetic activity without rewriting the DNA itself. Methylation changes have already been linked to genes used in chromosome organization, maintaining cell integrity, and overall sperm development.
Concurrently, the team of researchers used regional data to assess men's exposure to outdoor air pollutants during the roughly three-month period of sperm production, known as spermatogenesis. These included common pollutants such as nitrogen dioxide, sulfur dioxide, fine particulate matter, and ozone. Although previous studies have identified a link between air pollution and sperm quality, geneticists still don't fully understand how these adverse effects manifest at the molecular level.
Researchers have identified ozone and nitrogen dioxide as some of the most influential pollutants. In urban areas like Salt Lake City, concentrations of these two substances often exceed standards due to natural gas combustion and vehicle emissions.
«"Our findings suggest that exposure to air pollution 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," said Carrie Nobles, a co-author of the study and an environmental scientist at the University of Massachusetts Amherst, in an accompanying statement.
Researchers identified 39 DNA methylation changes associated with air pollution, particularly in the gene GNAS — an imprinted gene associated with poor sperm quality and fetal development. However, as Nobles explained, the gene's significance GNAS «"especially important.".
«"Because imprinted genes can persist throughout early embryonic development, this raises important questions about whether environmental factors affecting fathers may influence not only fertility but also pregnancy and offspring health," she said.
As these are preliminary results, Nobles emphasized that it is crucial that researchers now work to replicate these findings in future studies. She also explained that further research is needed to determine the measurable impact on fertility and pregnancy in men, as well as to investigate other sources of pollution.
«"We know that couples exposed to air pollution often have difficulty conceiving, and this may be one of many explanations for how pollution affects our reproductive health," said former ESHRE chair Karen Sermon, commenting on the study.