AsianScientist (Nov. 30, 2017) – Scientists in China, Hong Kong, Taiwan and the Netherlands have reported that air pollution is associated with lower sperm quality. They published their findings in Occupational and Environmental Medicine.
Environmental exposure to chemicals is thought to be a potential factor in worsening sperm quality. In modern cities where air quality is often poor, people are chronically exposed to particulate matter in the air. Fine particulate matter under 2.5 micrometers in size, known as PM2.5, are especially harmful because they remain in the air for extended periods of time and can bypass the nose to enter the lungs and the bloodstream. However, the jury is still out on whether and how PM2.5 affects sperm quality.
In this study, a team of researchers led by Professor Chang Ly-Yun of Academia Sinica, Taiwan, looked at the impact on reproductive health of short- and long-term exposure to PM2.5 among nearly 6,500 men in Taiwan between the ages of 15 to 49 years.
The men had taken part in a standard medical examination program between 2001 and 2014, during which their sperm quality was assessed according to guidelines set out by the World Health Organization—the total numbers, shape, size and movement of sperm were documented. At the same time, PM2.5 levels for each man was estimated based on his home address, monitored for an average of two years with a new mathematical approach in combination with NASA satellite data.
A strong association between PM2.5 exposure and abnormal sperm shape was found. Every 5 µg/m3 increase in fine particulate matter across the two year average was associated with a significant drop in normal sperm size of 1.29 percent. PM2.5 exposure was also associated with a 26 percent heightened risk of being in the bottom 10 percent of normal sperm size and shape, after taking into account potentially influential factors, such as smoking, drinking, age or obesity.
However, the researchers observed significantly higher sperm numbers associated with PM2.5 exposure. They suggest that this could be a compensatory mechanism to combat the detrimental effects on sperm shape and size. Changes in sperm quality were evident after just three months of exposure to PM2.5.
The researchers noted that theirs was an observational study, so no firm conclusions can be drawn about cause and effect, and they were not privy to information on any previous fertility problems. While the precise manner in which air pollution could impair sperm development remains unclear, the scientists point out that 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.
Free radical damage, brought on by exposure to air pollutants, might also have a possible role, as free radicals 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, air pollution is clearly an important public health challenge,” the researchers emphasized.
“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,” they warned, calling for global strategies to minimize the impact of air pollution on reproductive health.
The article can be found at: Lao et al. (2017) Exposure to Ambient Fine Particulate Matter and Semen Quality in Taiwan.
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Source: BMJ; Photo: Shutterstock.
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