Air Pollution Fertility Risks for Future Generations
New research presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) has found that exposure to air pollution may alter the way genes function in sperm, raising important questions about male fertility, pregnancy outcomes and even the long-term health of future children.
The study is one of the largest of its kind to investigate how common outdoor air pollutants may influence sperm at a molecular level, adding to growing evidence that environmental factors can play a significant role in reproductive health.
How can air pollution affect sperm?
Researchers found that men exposed to higher levels of air pollution during spermatogenesis—the approximately three-month process during which sperm are produced—showed changes in DNA methylation within their sperm.
DNA methylation is a natural process that acts like a series of switches, helping turn genes on or off without changing the underlying DNA sequence itself. These tiny chemical changes can influence how genes function and may affect sperm development and early embryo development.
The changes identified in this study were linked to genes involved in:
- Sperm development
- Chromosome organisation
- Cellular quality control
- Early embryonic development
More than 2,000 men took part
The study analysed data from more than 2,000 men attending fertility clinics in Salt Lake City, Utah, between 2013 and 2017.
Participants provided semen samples over a six-month period, with researchers analysing sperm DNA from 1,220 men who completed the final follow-up.
Using residential air quality data, the research team estimated each participant’s exposure to common outdoor pollutants during sperm production, including:
- Ozone (O₃)
- Nitrogen dioxide (NO₂)
- Sulphur dioxide
- Fine particulate matter (PM2.5)
Ozone and nitrogen dioxide showed the strongest links
Researchers identified 39 changes in sperm DNA methylation associated with exposure to combinations of air pollutants.
Among the pollutants studied, ozone and nitrogen dioxide appeared to have the strongest influence.
One particularly important finding involved a gene called GNAS, which has previously been linked to poorer semen quality and plays an important role in embryo and fetal development.
Because GNAS is an imprinted gene—meaning only one copy inherited from either the mother or father is active—changes to its regulation could potentially influence early embryonic development.
Could a father’s environment affect future children?
Lead author Dr Carrie Nobles, Assistant Professor of Environmental Health Sciences at the University of Massachusetts Amherst, said the findings raise important questions about the wider impact of environmental exposures.
“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.”
She added that the findings relating to the GNAS gene were particularly significant.
“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.”
Pollution and fertility
Air pollution has increasingly been recognised as an important threat to human health.
Previous studies have already linked poor air quality with:
- Reduced sperm quality
- Lower sperm counts
- Increased oxidative stress
- Cardiovascular disease
- Respiratory illness
However, far less has been understood about how pollution may influence sperm at the genetic and epigenetic level.
This new research helps fill part of that gap.
More research is still needed
The researchers stress that these findings show an association, rather than proving that air pollution directly causes fertility problems or changes in offspring health.
Future studies will now need to determine whether these DNA methylation changes lead to measurable differences in fertility, pregnancy outcomes or children’s health.
The team also hopes future research will examine personal exposure to indoor pollution alongside outdoor air quality.
ESHRE expert: Another important piece of the puzzle
Professor Karen Sermon, Immediate Past Chair of ESHRE, said the findings add to an expanding body of evidence linking environmental pollution with reproductive health.
“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 amongst the myriad ways that pollution impacts our reproductive health.”
What does this mean for people trying to conceive?
While it’s impossible to eliminate all exposure to air pollution, the findings highlight how important overall health and environmental factors may be for fertility.
Male fertility is influenced by many factors including:
- Smoking
- Alcohol consumption
- Diet and nutrition
- Exercise
- Body weight
- Stress
- Heat exposure
- Environmental pollutants
Because sperm take around three months to develop, positive lifestyle changes made today may help improve sperm health in the months ahead.
As scientists continue to learn more about the relationship between our environment and fertility, studies like this provide valuable insight into how both partners’ health before conception may influence pregnancy and future generations.
Source: Research presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) and published in Human Reproduction.
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