Air pollution may be causing infertility for a ‘significant number of couples’ a new study suggests.

Researchers looked at 6,500 men living in Taiwan and found that higher pollution was linked to poorer quality sperm.

The study showed that for every 5 ug/m3 increase in tiny particles called PM2.5s, there was a 26 per cent increased risk of being in the bottom 10 per cent of normal sperm size and shape.

The effect was found when particle counts rose over 25 ug/m3 . In London yesterday, particulates rose to 69 ug/m3 in some areas.

Although it is unclear how the pollution impacts sperm, researchers say that the components of fine particulate matter, such as heavy metals and polycyclic aromatic hydrocarbons, have been linked to sperm damage in experimental studies.

Free radical damage, brought on by exposure to air pollutants, may also damage DNA and alter cellular processes in the body, the researchers suggest.

“Although the effect estimates are small and the significance might be negligible in a clinical setting, this is an important public health challenge,” said Dr Xiang Qian Lao of the Chinese University of Hong Kong.

“Given the ubiquity of exposure to air pollution, a small effect size of PM2.5 on sperm normal morphology may result in a significant number of couples with infertility.”