Air Pollution Might Explain the 30% of Infertility With No Known Cause: Large Chinese Study
Exposure to air pollution may be a leading factor behind infertility, according to a new, large-scale study out of China. The finding may help shed light on why approximately 30% of infertile couples have fertility issues that can’t be explained by hormonal imbalances, poor sperm quality, or any other known cause.
Over the last two decades, about 10% of the global population has been affected by infertility, and evidence suggests this rate is on the rise. In India, infertility affects about 10% to 14% of the population. In recent years, air pollution has been thought to play a role in infertility, as lower fertility has been found to be most common in places where air pollution has increased. Among the pollutants, PM 2.5 was suspected as most damaging, because of its serious consequences on other aspects of human health. However, no study had found a direct link until now.
Researchers in China found that exposure to airborne particulate matter increases by up to 20% the likelihood of infertility, defined as not becoming pregnant within a year of unprotected sexual intercourse. They also found the proportion of women not becoming pregnant after a year of trying rising from 15% to 26% between least-polluted and most-polluted areas. These findings, the researchers hope, inform more effective reproductive policies.
While the research did not assess the particular mechanisms which lead to a decrease in fertility, multiple studies have shown that air pollution affects the number of viable eggs in ovaries and reduces sperm count. “Further studies are required to evaluate potential mechanisms and confirm the association between air pollution and fecundity decrements, which might be responsible for increased infertility rates in areas with heavy PM2.5 pollution,” said the study.
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This study, published in the science journal Environment International, was based on data from more than 18,000 couples in China. The researchers took account of their reproductive information, sociodemographic characteristics such as age, weight, income, and lifestyle patterns including smoking, alcohol drinking, and exercise levels. Then, after estimating each participant’s PM 2.5 exposure levels across 1-year, 3-year, and 5-year and adjusting the data for other factors that contribute to fertility struggles, they reached the conclusion.
Previous studies had produced mixed results. But unlike older studies that were based on smaller samples, the researchers say that their samples were recruited from the general population, making the findings more generalisable.