The impact of air pollution on fertility treatment outcomes

Many factors influence fertility treatment success, including maternal age, ovarian reserve, sperm and embryo quality and clinical practice. Researchers are also increasingly examining whether environmental exposures may be a relevant factor.

Air pollution is already recognised as one of the largest environmental risks to human health. Long-term exposure has been firmly linked to cardiovascular and respiratory diseases, contributing to adverse health outcomes and shortened life expectancy worldwide. Evidence of its effects on reproduction is now accumulating too: polluted air has been associated with poorer semen quality, reduced ovarian reserve, longer time to pregnancy and a higher risk of miscarriage. In parallel, several studies have reported lower success rates among fertility patients living in more polluted areas.

However, previous research into air pollution and fertility treatment has often concentrated on individual clinics, cities or countries. These studies can provide important evidence within a particular setting, but a comparison across several regions offers a wider perspective. It allows researchers to examine whether the same broad association appears across populations with different healthcare systems, fertility practices and pollution levels.

As a research intern, now in Grade 11 at Taipei American School, I had the opportunity to help conduct such a study, looking into how ambient PM2.5 levels relate to fertility treatment outcomes across three continents. Starting in August 2025, I joined a team of researchers from the Taiwan IVF Group and Ton Yen General Hospital, supervised by Barry Behr, professor emeritus at Stanford University, California.

Our research focused on fine particulate matter, which is associated with particularly significant health risks. Commonly known as PM2.5, this air pollutant consists of particles measuring 2.5 micrometres or less in diameter. Exposure has been linked to oxidative stress and inflammation in both laboratory and clinical studies, two possible pathways through which air pollution could affect fertility.

Environmental data from the World Health Organisation, the European Environment Agency and NASA allowed us to track ambient PM2.5 exposure across Europe, North America and East Asia between 2010 and 2022. In parallel, we examined publicly available fertility treatment registry data in these regions across the same period, which provided regional information on clinical pregnancy and live birth rates.

Across all three regions, the same broad pattern emerged: areas with higher PM2.5 exposure tended to have poorer fertility treatment outcomes.

We grouped regions according to their pollution exposure and compared those in the highest and lowest exposure quartiles. This provided a clear way to examine how clinical pregnancy and live birth rates differed between areas with relatively high and relatively low PM2.5 levels.

In Europe, regions in the highest exposure quartile had clinical pregnancy rates four to eight percent lower and live birth rates three to seven percent lower than those in the lowest quartile. In North America and East Asia, the corresponding differences were approximately five to 12 percent for clinical pregnancy and four to ten percent for live birth.

These figures varied in size between regions, but the direction of the association remained the same. The estimated association size (that is, the strength of the relationship between PM2.5 levels and fertility treatment outcomes) also changed between regions, but there was no evidence of a statistically significant difference between continents. Importantly, the overall pattern remained consistent: higher PM2.5 exposure was associated with lower clinical pregnancy and live-birth rates across Europe, North America and East Asia.

This cross-continental consistency is notable because the three regions differ in their populations, healthcare systems, fertility practices, environmental conditions and levels of air pollution. The results suggest that the observed relationship was not confined to a single geographic setting or one particular model of fertility care.

As a population-level analysis, the study cannot establish a direct causal relationship between PM2.5 exposure and fertility treatment outcomes in individual patients. Regional differences in patient characteristics, treatment practices, socioeconomic factors and other environmental exposures may also have contributed to the lower success rates seen in more polluted areas. More precise exposure estimates combined with individual-patient data would allow researchers to determine whether the association persists after differences in patient characteristics and fertility treatment practices are taken into account.

Nevertheless, the consistency of the association across three geographically, populationally and clinically distinct regions strengthens the rationale for investigating air pollution as a potentially modifiable environmental factor in fertility treatement success, as well as in reproductive health in general.

Modern IVF laboratories commonly use high-efficiency particulate air filtration and other air-quality controls to minimise airborne contaminants and maintain stable conditions for fertilisation and embryo culture. However, patients are exposed to ambient air pollution outside the laboratory before and throughout treatment. This exposure may have a detrimental impact on reproductive success via pathways that could potentially involve sperm or oocyte quality, the uterine environment or implantation

Future patient-level studies incorporating more precise exposure measurements will be important to clarify how PM2.5 exposure influences fertility treatment success, and identify the biological mechanisms involved. Research could examine exposure at specific stages of fertility treatment, including before ovarian stimulation, during treatment and around the time of embryo implantation, as well as possible mechanisms involving oxidative stress and inflammation.

In July 2026 in London, I presented the findings of this study during a poster discussion session at the Annual Meeting of the European Society of Human Reproduction and Embryology. Standing in front of clinicians and scientists from around the world and fielding their questions was both daunting and energising, and it showed me how much interest there is in the environmental side of reproductive medicine.

Participating in this research allowed me to see how large-scale data analysis can uncover meaningful patterns in reproductive medicine and environmental health. It has motivated me to keep working at the intersection of the two, with the hope that a better understanding of what patients are exposed to outside the clinic can eventually improve what happens inside it.