(London, United Kingdom) New research presented today at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) suggests that exposure to air pollution may impact genes associated with sperm development, raising new questions about male fertility, pregnancy outcomes and offspring health.[1]
In one of the largest studies of its kind, researchers found that men exposed to mixtures of common air pollutants during sperm development showed changes in sperm DNA methylation – chemical modifications that regulate gene activity without altering the DNA itself. The methylation changes were linked to genes involved in key reproductive and cellular processes, including sperm development, chromosomal organisation and cellular quality control.
The secondary data study included more than 2,000 men between 2013 and 2017 in Salt Lake City, Utah. Participants provided semen samples at enrolment and after 2, 4 and 6 months. Sperm DNA methylation was analysed in the 1,220 men who provided a sample at the six-month follow-up visit.
Researchers estimated participants’ exposure to outdoor air pollutants during spermatogenesis – the approximately three-month process of sperm production – including ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide and fine particulate matter (PM2.5).
Researchers identified 39 DNA methylation changes associated with air pollution mixtures, with ozone and nitrogen dioxide emerging as the strongest contributors. Among the most notable findings was altered methylation in GNAS , an imprinted gene previously associated with poorer semen quality and implicated in embryonic and foetal development.[2,3]
Air pollution is increasingly recognised as a major threat to human health, with growing evidence linking exposure to cardiovascular, respiratory and reproductive health effects.[4] Previous studies have associated air pollution with poorer semen quality, but far less is known about how these exposures may influence sperm at the molecular level.[5]
Lead author Dr Carrie Nobles explained, “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.”
Discussing the significance of the findings, Dr Nobles said, “The association with changes in the imprinted gene GNAS was particularly important. 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.”
Dr Nobles noted that air pollution is a complex mixture that varies by season and location, with nitrogen dioxide and ozone often elevated in urban areas due to traffic emissions and natural gas combustion.
“A critical next step is replication of findings in other studies,” Dr Nobles added. “We also need to understand whether air pollution-associated changes in sperm DNA methylation have measurable downstream impacts on men’s fertility and couples’ pregnancy health. Future research should also explore the role of indoor and personal air pollution exposure.”
Commenting on the significance of the study, Professor Dr Karen Sermon, Immediate Past Chair of ESHRE, said: “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.”
The study abstract will be published today in Human Reproduction , one of the world’s leading reproductive medicine journals.
ENDS
Notes to editors:
A reference to the ESHRE Annual Meeting must be included in all coverage and/or articles associated with this study.
For more information or to arrange an expert interview, please contact the ESHRE Press Office at: press@eshre.eu
About the study author:
Dr Carrie Nobles is a reproductive and environmental epidemiologist studying the impacts of ambient environmental risk factors on men’s and women’s reproductive health. She is an Assistant Professor in the Department of Environmental Health Sciences in the School of Public Health and Health Sciences at the University of Massachusetts Amherst.
About the European Society of Human Reproduction and Embryology:
The main aim of ESHRE is to promote interest in infertility care and to aim for a holistic understanding of reproductive biology and medicine.
ESHRE collaborates world-wide and advocates universal improvements in scientific research, encourages and evaluates new developments in the field, and fosters harmonisation in clinical practice. It also provides guidance to enhance effectiveness, safety and quality assurance in clinical and laboratory procedures, psychosocial care, and promotes ethical practice. ESHRE also fosters prevention of infertility and related educational programmes and promotes reproductive rights regardless of the individual’s background. ESHRE’s activities include teaching, training, professional accreditations, mentoring and career planning for junior professionals, as well as developing and maintaining data registries. It also facilitates and disseminates research in human reproduction and embryology to the general public, scientists, clinicians, allied personnel and patient associations.
Website: https://www.eshre.eu/
About Human Reproduction:
Human Reproduction is a monthly journal of ESHRE and is one of the top three journals in the world in the field of reproductive biology, obstetrics and gynaecology. It is published by Oxford Journals, a division of Oxford University Press.
References:
[1] Nobles, C., et al. (2026). Exposure to air pollution mixtures during spermatogenesis and sperm DNA methylation in men seeking infertility treatment. Human Reproduction.
[2] Tang Q, Pan F, Yang J, et al. (2018). Idiopathic male infertility is strongly associated with aberrant methylation of imprinted genes in sperm: a case-control study. Clin Epigenetics. 10:134.
[3] Wang L, Zhang J, Duan J, et al. (2017). Altered GNAS imprinting due to folic acid deficiency contributes to poor embryo development and abnormal foetal outcomes. Oncotarget . 8(38):64901–64917.
[4] World Health Organization. (2025). Air pollution . https://www.who.int/health-topics/air-pollution
[5] Omolaoye, T. S., du Plessis, S. S., & Ramsay, M. (2024). Implications of exposure to air pollution on male reproduction. Antioxidants, 13 (1), 92. https://doi.org/10.3390/antiox13010092