Researchers said breathing polluted air can result in a "steep reduction in verbal and math scores."
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The study, published in the Proceedings of the National Academy of Sciences, found air pollution led to cognitive problems, particularly in older men.
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Those cognitive problems can lead to dementia and other mental health concerns.
The data is based on nearly 32,000 people over a four-year period in China.
"The damage on the aging brain by air pollution imposes substantial health and economic costs ..." researchers said.
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According to the World Health Organization, nine out of every 10 people on the planet breathe air containing a high level of pollutants, with Africa and Asia being the worse affected regions.