Air pollution is estimated to kill 7 million people prematurely each year, due to its well-known negative effects on the cardiac and respiratory systems. But even for those left alive, dirty air has a profound impact on brain function, according to research published on Monday in Proceedings of the National Academy of Sciences.
Led by Xin Zhang, a health and economics expert at Peking University, the study overlays two comprehensive datasets—the China Family Panel Studies (CFPS) surveys and the air pollution index (API)—to isolate the influence of dirty air on cognitive ability across 162 Chinese counties. The CFPS questionnaires are completed by tens of thousands of Chinese citizens, and include math and verbal aptitude assessments. The API is generated from daily readings of major air pollutants in Chinese cities, which are collected and published by the Chinese Ministry of Environmental Protection.
Zhang’s team amassed over 25,000 completed CFPS surveys from the years 2010 and 2014, and matched them with API data from the same cities and timeframes. The researchers found that low test scores correlated to high air pollution, and that verbal scores in particular dropped between 2010 and 2014 in regions with increasingly dirty air.
The decline in cognitive abilities was especially noticeable in aging and elderly people, who are more vulnerable to neurodegenerative diseases. Men, particularly uneducated men, also experienced greater decreases in cognitive function compared to women. The authors speculate that this could be due to the female brain’s slightly larger abundance of white matter, which is crucial to verbal tests.
“Our findings about the damaging effect of air pollution on cognition, particularly on the aging brain, imply that the indirect effect on social welfare could be much larger than previously thought,” the team concluded. “A narrow focus on the negative effect on health may underestimate the total cost of air pollution”
The authors also calculated that if the same air quality standards upheld by the US Environmental Protection Agency were adopted in China, verbal test scores would be boosted 2.41 points while the math scores would rise 0.39 points.
China has been actively trying to curb its air pollution, and the nation’s efforts are beginning to pay off. But given that about 91 percent of the global population is exposed to air that fails World Health Organization quality standards, this is a problem that extends beyond any one country’s borders. Air pollution will have to be tackled on a worldwide level, so that future generations will not only be able to breathe freely—but also think clearly.
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