The effect of air quality on fertility

Infertility affects millions of couples around the world but relatively little research has been done on the impact of air pollution. However, dirty air is already known to increase the risk of premature birth and low birth weight. Common levels of nitrogen dioxide are as bad as smoking in raising the risk of miscarriage and pollution particles have been found on the foetal side of placentas.

Right, so what do we know?

A study in China has found that high pollution levels can increase the risk of infertility by up to 20%. The analysis of 18,000 couples in China found that those living with moderately higher levels of small-particle pollution had a 20% greater risk of infertility. Infertility is defined as not becoming pregnant within a year of trying.

Why is this?

Pollution particles are known to cause inflammation in the body, which could damage egg and sperm production.

Men living in areas with higher air pollution are more likely to have a higher proportion of abnormally shaped sperm. Researchers from the Chinese University of Hong Kong analysed sperm quality in samples from more than 6500 Taiwanese men between the ages of 15 and 49. They paired this data with satellite imaging data to determine the levels of air pollution around their homes. They found a robust association between exposure to high air pollution and low percentage of sperm normal morphology in reproductive-age men.

Another recent study of 600 women attending a US infertility clinic found that increased exposure to air pollution was associated with a lower number of maturing eggs in the ovaries.

Is this something to worry about in the UK?

We should note that the level of air pollution in cities in Taiwan and China is generally higher than in cities in the UK. The average pollution level for the Chinese couples was 57µg/m3 whereas in London the average is about 13µg/m3.

Professor Allan Pacey, an andrology researcher at the University of Sheffield, added: 'From this and other studies, I remain of the opinion that air pollution probably does have the potential to negatively influence male reproductive health.

But the jury is still out...'