Previous research has shown that sperm counts for men living in North America, Australia, and Europe have been declining since the 1970s. Why? There are only theories, not confirmations, and the results have often been mixed.
Now, a team of researchers from the Shanghai Tongji University School of Medicine (China) has carried out a study to answer this question, concluding that there is an association between air pollution and semen quality. .
Scientists studied 33,876 male patients at fertility clinics in 130 cities in China and found that those who lived in areas with higher levels of particulate matter, or airborne particles, tended to have poorer sperm quality, especially in the regarding sperm motility, the sperm’s ability to ‘swim’ or move in the right way.
The investigation
First, they separated the patients into four groups based on the degree of air pollution in the areas where they lived. Next, they studied the results of sperm examination performed by doctors at fertility clinics. They focused on sperm count, degree of concentration, and motility.
After this, they could not find any connection between the number of sperm produced by the patients, nor the concentrations of sperm and the levels of air pollution. However, they did see patterns related to motility. Patients who lived in areas of high concentrations of the smallest types of particles had the highest sperm motility. So much so, that patients exposed to airborne particles smaller than 2.5 micrometers had an average 3.6% decrease in motility compared to the average man in China. In men exposed to larger particles (up to 10 micrometers in diameter), the average drop in motility was 2.44%.
The research, which has been published in JAMA, also suggests that the smaller the size of contaminant particles in the air, the greater the link to poor semen quality.
“Our findings suggest that smaller suspended particle size fractions may be more potent than larger fractions in inducing poor sperm motility,” the authors wrote.
Study limitations
In any case, apart from air quality, among the factors that influence sperm quality are also age, body mass index, body fat or alcohol consumption, so the study presents some limitations and its results should be taken with some caution. There is not yet enough data to infer a significant clinical effect overall and cause a reduction in their chances of becoming parents.
What factors determine the quality of sperm?
They are three:
Sperm count: the number of sperm. The lower the sperm count, the lower the chance of conceiving.
Sperm Mobility: The ability of the sperm to navigate through the cervix, uterus, and fallopian tubes and reach the egg for fertilization. Less sperm mobility will lead to lower fertility.
Sperm structure: Also known as sperm morphology, it is the correct structure (tail and head) of the sperm that is essential to aid motility. A better structure implies a better quality of sperm.
Did you know that abnormal sperm have head or tail defects, such as a misshapen head or a double tail?
Referencia: Yan Zhao et al, Association of Exposure to Particulate Matter Air Pollution With Semen Quality Among Men in China, JAMA Network Open (2022). DOI: 10.1001/jamanetworkopen.2021.48684
