Air pollution may explain regional gaps in sperm quality,

By Stephen Beech

Marked differences in sperm quality among men with similar lifestyles may be down to air pollution levels where they live, suggests a new study.

Researchers found "substantial" regional differences in sperm quality, with men in the highest-performing region recording almost double the total healthy sperm count of those in the worst region.

Lifestyle habits were broadly similar across regions and didn't explain the differences, raising questions about the role of environmental pollution exposure in male reproductive health.

Researchers analyzed semen quality and lifestyle data from 386 men undergoing fertility assessment across seven assisted reproduction centers in Spain between June 2024 and December 2025.

Participants completed a questionnaire covering factors including residence, body mass index (BMI), medical history, physical activity, chemical exposure, medication use, smoking, alcohol, drug and coffee consumption.

Researchers then compared semen parameters across four regions of Spain — north, south, southeast and central — to determine whether geographical differences in sperm quality could be explained by lifestyle or socio-demographic factors.

The results revealed "significant" regional differences in semen volume, sperm concentration, motility, morphology and total motile sperm count, as well as the prevalence of asthenozoospermia — reduced sperm motility — and teratozoospermia, abnormal sperm morphology.

Men living in northern Spain recorded the strongest semen quality overall, with an average total motile sperm count of 94.35 million, compared with 50.11 million in central Spain.

The northern region also had the highest average sperm concentration and sperm motility (44.79%).

Reduced sperm motility affected 23.9% of men in the north, compared with 55.4% in southern Spain and 53.4% in central Spain.

Despite the differences in semen quality, lifestyle habits and overall lifestyle patterns were broadly similar across the four regions studied.

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After adjustment for all measured lifestyle and socio-demographic factors, only geographical location and abstinence duration remained independently associated with semen parameters.

Total motile sperm count was independently associated with both geographical location and abstinence duration, while geographical location alone remained significantly associated with the prevalence of reduced sperm motility and abnormal sperm morphology.

Study lead author Professor Rocío Núñez-Calonge said: "What was most remarkable for us was that the strongest semen quality parameters were consistently found in northern Spain.

"At the same time, we were surprised to find that lifestyle habits were very similar across all the geographical areas studied.

"If, based on the results of this study, we rule out male lifestyle habits as the explanation for the geographical differences observed in semen quality, it seems likely that these variations may instead be related to differences in environmental exposure, such as levels of pollution or other environmental contaminants present in those areas."

She noted that the findings may have implications beyond Spain, with studies from several countries reporting significant regional variations in semen quality, particularly in areas with marked environmental variations.

Núñez-Calonge, scientific advisor at the International Reproduction Unit based in Alicante, said: "Given the widespread presence of air pollution in many urban environments, its potential effects on male fertility deserve further investigation."

She added: "Larger and well-designed studies are needed to better clarify the relationship between environmental exposure and semen quality.

"At the same time, stronger public health policies aimed at reducing exposure to pollutants, industrial chemicals and plastic-derived compounds should be considered as a priority for protecting reproductive health in future generations."

The findings, published in the journal Human Reproduction, are due to be presented at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in London.

Professor Karen Sermon, ESHRE immediate past chair, said: "While it is well established that a healthy lifestyle has a positive effect on sperm quality, the effect of environmental factors that are beyond the control of the individual are clear and need to be tackled at societal and political level."

She added: "There is a clear responsibility for national and EU regulators in this matter."