The Economist reports on a study from researchers at Peking University (the Harvard of China) in Beijing: https://www.economist.com/science-and-technology/2018/08/30/older-men-are-more-prone-to-cognitive-impairment-from-dirty-air
Summary: The team of researchers consisting of Xiaobo Zhang, Xin Zhang and Xi Chen "looked at tests carried out as part of the China Family Panel Studies (CFPS), a survey by Peking University. In 2010 and 2014 the same group of around 20,000 people were tested in standardised mathematics and given a verbal test in word recognition. Crucially, the CFPS logged precise information about the date and location of each test."
"Putting this information together allowed the researchers to match test scores at each location with the local air quality as reported by the air-pollution index, a measure that rates pollution levels in different cities across China based on daily readings of sulphur dioxide, nitrogen dioxide and tiny bits of particulate matter. The index ranges from zero to 500, signifying the highest level of pollution."
"As they report in Proceedings of the National Academy of Sciences, the researchers showed that chronic exposure to pollution lowered the scores on the verbal tests, and that the higher the pollution levels were the more the scores dropped."
In addition, the results indicated that men were more affected than women and that poorer men were most affected. One of the researchers theorized that "pollutant damage is probably accumulating in the white matter of the brain, which people depend upon more heavily for verbal tasks; and men have less white matter than women. It is possible, too, that men with a poor education may work outside, and are thus more exposed to air pollution."