Countries all across the world are attempting to combat the threat of air pollution. In the midst of this conflict, a new Chinese study claims that air pollution can damage male fertility by lowering sperm motility, or the ability of sperm to swim in the right direction.
The study, which was published in the journal JAMA Networks, looked at data from over 30,000 Chinese males and found that exposure to particulate matter with a diameter of less than 2.5 m and a diameter of less than 10.0 m can cause low sperm motility and increase the incidence of asthenozoospermia (a medical term for the reduced sperm motility in semen, when the sperm is unable to reach and fertilise the egg).
Researchers at the School of Medicine of Tongji University in Shanghai studied data records of 33,876 men from 340 Chinese cities, aged 34 on average, with a varied degree of exposure to air pollution. These men and their wives got pregnant through assisted reproduction technology between January 2013 and December 2019.
The cities where these men lived had median levels of PM2.5, PM2.5-10, and PM10 pollution. It was found in the study that an increase in PM 2.5 exposure results in 3.6 percent decrease in sperm motility and an increase in PM10 exposure results in 2.44 percent decrease in sperm motility. However, no significant associations were observed between PM exposure and sperm count or concentration.
The study further observed the effect of pollution on sperm in different stages of its development. The three key stages were — spermatogenesis (when the sperm is made), sperm motility development (when the sperm develops ability to swim), and epididymal storage (when the sperm is stored).
The effects of PM2.5 and PM10 for the period of spermatogenesis were significantly larger than the periods of sperm motility development and epididymal storage. This indicates that the effect may be genetic.
The study suggests that an increase in PM2.5 to PM10 exposure increases the odds of asthenozoospermia by 14 percent and 9 percent, respectively.
Allan Pacey, professor of andrology at the University of Sheffield, who is not involved in the study said, “The possibility of a link between air pollution and semen quality has been suggested in a number of studies over the years, although not all of them have agreed with this conclusion.”
According to Pacey, the findings of the study need to be taken with a pinch of salt as there isn’t enough information to infer that pollution has a significant negative clinical effect at large. More research out in the field might help answer that question with more certainty in the future.