New Delhi: Air pollution, particularly levels of fine particulate matter (PM 2.5), is associated with poorer quality sperm and may lead to infertility, according to a study published in international journal Occupational & Environmental Medicine on Tuesday.

The researchers said that although the size of the effect is relatively small in clinical terms, given how widespread air pollution is, this might spell infertility for a “significant number of couples".

“Environmental exposure to chemicals is thought to be a potential factor in worsening sperm quality, but the jury is still out on whether air pollution might also have a role. To explore this possibility further, the international team of researchers looked at the impact on health of short and long term exposure to fine particulate matter (PM 2.5) among nearly 6,500 (15 to 49 years old) men in Taiwan," said an official statement.

The men were all taking part in a standard medical examination programme between 2001 and 2014, during which their sperm quality was assessed (total numbers, shape/size, movement) as set out by the guidelines of the World Health Organization (WHO).

The study explained that PM 2.5 levels were estimated for each man’s home address for a period of three months, as that is how long it takes for a sperm to be generated, and for an average of two years, using a new mathematical approach combined with NASA satellite data.

“A strong association between PM 2.5 exposure and abnormal sperm shape was found. Every 5 ug/m3 increase in fine particulate matter across the 2 year average was associated with a significant drop in normal sperm shape/size of 1.29%," the study said.

“And it was associated with a 26% heightened risk of being in the bottom 10% of normal sperm size and shape, after taking account of potentially influential factors, such as smoking and drinking, age or overweight," the study added.

“However, it was also associated with a significant increase in sperm numbers, possibly as a compensatory mechanism to combat the detrimental effects on shape and size," the researchers suggested.

Similar findings were evident after three months of exposure to PM 2.5.

It, however, clarified that it is an observational study and thus no firm conclusions can be drawn about cause and effect.

“And exactly how air pollution could impair sperm development is not clear. But many of the components of fine particulate matter, such as heavy metals and polycyclic aromatic hydrocarbons, have been linked to sperm damage in experimental studies," the researchers pointed out in the study.

They suggested that free radical damage, brought on by exposure to air pollutants, might have a possible role, as this can damage DNA and alter cellular processes in the body.

“Although the effect estimates are small and the significance might be negligible in a clinical setting, this is an important public health challenge," the study stated.

“Given the ubiquity of exposure to air pollution, a small effect size of PM 2.5 on sperm normal morphology may result in a significant number of couples with infertility," the study warned and called for global strategies to minimize the impact of air pollution on reproductive health.

PM 2.5 (particulate matters less than 2.5 micron) is one of the deadliest components of air pollution. It is a fine particle that can settle deep in the lungs and be absorbed in the bloodstream, which can lead to respiratory problems, cardiovascular diseases and lung cancer. A recent report by The Lancet had said that more than half a million Indians are estimated to have died prematurely in 2015 due to PM2.5 air pollution.

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