Air pollution may negatively affect male fertility: Study
Air pollution may negatively affect semen quality, particularly the ability of sperm to swim in the right direction, according to the findings of a new research, The Guardian reported.
The study was conducted at the School of Medicine of Tongji University in Shanghai through analysing samples collected from a total of 33,876 men -- aged 34 on average -- whose wives conceived through assisted reproduction technology with their sperm between January 2013 and December 2019.
The samples were collected from 340 Chinese cities, with a varied degree of exposure to air pollution among them, according to The Guardian report.
Sperm motility -- the sperm's ability to swim inside the reproductive tract -- is one of the factors that determine semen quality.
The study suggested that the smaller the size of the particulate matter that cause air pollution, the greater the link with poor semen quality.
The researchers studied the factors such as sperm count, concentration, and sperm motility of the samples to establish the quality of the semen.
"Our findings suggest that smaller particulate matter size fractions may be more potent than larger fractions in inducing poor sperm motility," the authors wrote in the paper, adding that it highlighted the need to reduce exposure to air pollution among men in their reproductive age.
Although researchers have long been studying if there is any possible link between air pollution and sperm quality, the findings lacked consistency and were complicated to put into perspective regarding adverse health effects on male fertility.
The new research studied patterns between semen qualities in correlation with the participants' extent of exposure to air pollution from particulate matter of diameter smaller than 2.5 micrometres, between 2.5 and 10 micrometres, and 10 micrometres.
The study revealed that both the progressive and the total sperm motility were lower among samples of participants who were exposed to smaller particulate matter, according to The Guardian report.
Those exposed to particulate matter smaller in diameter than 2.5 micrometres saw an estimated decrease in sperm motility of 3.6%, compared to 2.44% less sperm motility when exposed to particulate matter of 10 micrometres in diameter.
The researchers, however, did not find any link between air pollution and sperm count or concentration, the report read.
"This paper adds to the evidence base suggesting the link is real, and is impressive because it uses semen quality data from over 30,000 men," Allan Pacey, a professor of andrology at the University of Sheffield, told The Guardian.
"But the level of decline in sperm motility seems to be quite low," Pacey, who was not involved in the study, also said.
He stressed that correlation is not causation, and noted that the paper could not provide any conclusive evidence to determine whether air pollution might be responsible for reduced sperm motility, or there may be other reasons.
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