Expert says air pollution may harm fertility and could be one reason some couples struggle to conceive.
Exposure to air pollution may do more than harm the lungs and heart—it could also change how genes function in sperm, potentially affecting male fertility, pregnancy outcomes, and even the health of future generations, according to new research. ()
The findings, presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) and published in the journal Human Reproduction, suggest that common air pollutants can alter DNA methylation in sperm, a biological process that regulates gene activity without changing the underlying DNA sequence.
Researchers say the study provides new evidence that environmental pollution may influence reproductive health at the molecular level, although further research is needed to determine whether these changes directly affect fertility or child development.
How Air Pollution Can Affect Sperm
Sperm production, known as spermatogenesis, takes around three months. During this period, developing sperm cells can be influenced by environmental exposures, including air pollution. Rather than causing mutations in DNA, pollutants appear to affect DNA methylation—a process in which small chemical tags called methyl groups attach to DNA and influence whether certain genes are switched on or off.
These epigenetic changes do not alter the genetic code itself but can affect how genes function. Scientists believe some of these changes may persist during early embryonic development, potentially influencing pregnancy and offspring health.
How Researchers Studied the Impact of Air Pollution
The study is one of the largest investigations to examine how air pollution affects sperm at the molecular level. Researchers analyzed data from more than 2,000 men who participated in a reproductive health study conducted in Salt Lake City, Utah, between 2013 and 2017.
Participants provided semen samples when they enrolled in the study and again after two, four, and six months. DNA methylation was analyzed in the sperm samples of 1,220 men who completed the six-month follow-up. The researchers also estimated each participant’s exposure to outdoor air pollutants during the period of sperm development. They measured exposure to ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and fine particulate matter (PM2.5).
Ozone and Nitrogen Dioxide Showed the Strongest Effects
The analysis identified 39 DNA methylation changes associated with exposure to mixtures of air pollutants. Among all the pollutants studied, ozone and nitrogen dioxide emerged as the strongest contributors to these molecular changes.
Many of the affected genes are involved in critical biological processes, including sperm development, chromosome organization, and cellular quality control, suggesting that air pollution may interfere with the normal development of healthy sperm.
Why the GNAS Gene Matters
One of the most significant findings involved changes in the GNAS gene, an imprinted gene that has previously been linked to reduced semen quality and plays an important role in embryonic and fetal development.
Unlike most genes, imprinted genes retain information about whether they were inherited from the mother or the father. Because these genes remain active during the earliest stages of embryonic development, changes in their regulation could potentially influence pregnancy outcomes and the health of future children.
Lead author Dr. Carrie Nobles said the findings highlight the importance of understanding how environmental exposures may influence reproductive health. “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,” Nobles said.
She added that changes observed in the GNAS gene were particularly noteworthy. “Because imprinted genes can persist through early embryonic development, this raises important questions about whether fathers’ environmental exposures may influence not only fertility, but pregnancy and offspring health,” she said.
Air Pollution Is an Increasing Reproductive Health Concern
Air pollution has already been linked to a wide range of health problems, including cardiovascular disease, respiratory illnesses, and reproductive disorders.
Previous studies have shown that men exposed to higher levels of air pollution often have poorer semen quality. However, scientists say much less has been known about the biological mechanisms that could explain these effects.
According to the researchers, the current findings help bridge that knowledge gap by showing that pollution may alter gene regulation in sperm, potentially affecting reproductive health in ways that extend beyond traditional measures such as sperm count or motility.
Experts Say More Research Is Needed
Dr. Nobles emphasized that air pollution is a complex mixture of pollutants whose composition varies by location and season. In urban environments, nitrogen dioxide and ozone are commonly produced by traffic emissions and natural gas combustion, making them particularly relevant to public health.
She said future studies should investigate whether these DNA methylation changes have measurable effects on male fertility, pregnancy success, and children’s health, while also examining the role of indoor air pollution and personal exposure.
Commenting on the findings, Karen Sermon, Immediate Past Chair of ESHRE, described the research as an important step toward understanding how pollution affects human reproduction.
“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 affects our reproductive health,” Sermon said.
Reducing Exposure to Air Pollution
While it is impossible to eliminate exposure completely, experts recommend several practical steps to reduce the health risks associated with air pollution:
- Check daily air quality reports and limit outdoor activities when pollution levels are high.
- Use indoor air purifiers to reduce pollutants inside homes.
- Wear well-fitted protective masks designed to filter airborne particles during periods of poor air quality or heavy pollution.
- Avoid strenuous outdoor exercise near busy roads or during peak traffic hours, when pollution levels are often highest.
Although the study does not prove that air pollution directly causes infertility, it adds to growing evidence that cleaner air may play an important role in protecting reproductive health.
Researchers say larger studies in different populations are now needed to confirm the findings and determine whether these molecular changes translate into measurable effects on fertility, pregnancy outcomes, and the health of future generations.
References:
- Exposure to air pollution mixtures during spermatogenesis and sperm DNA methylation in men seeking infertility treatment – (https://academic.oup.com/humrep/article/41/Supplement_1/deag083.203/8727607)
Source-Medindia