Air Pollution May Boost Risk of Cognitive Decline

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It’s well known that air pollution contributes to many health problems, including heart disease, asthma, and other respiratory disorders. But evidence is accumulating that it can also harm the brain, especially as people age, contributing to cognitive decline and dementia.

In a study in the Proceedings of the National Academy of Sciences (PNAS) in September 2018, researchers found that people in China who had high exposure to air pollution in recent years performed worse on standard tests of verbal and math ability compared with people who had less exposure. The longer they were exposed to heavily polluted air, the more pronounced the effect, especially among older adults. Pollution seemed to have a worse effect on verbal than math performance, especially in men.

Closer to home, a working paper from the nonprofit National Bureau of Economic Research, published online in August 2018, analyzed the human and economic costs of the air pollution/dementia link. Using 15 years of Medicare records for almost 7 million U.S. adults, plus EPA air-quality data from the same period, economists correlated people’s cumulative exposure to fine particle air pollution (PM2.5, meaning particulate matter smaller than 2.5 microns) with their incidence of dementia. Sources of PM2.5 include motor vehicle exhaust, power plants, wildfires, tobacco smoke, and any other burning of fuels such as wood, oil, or coal.

They found that long-term exposure to elevated PM2.5 levels-even levels well below the federal maximum allowable thresholds-was associated with a markedly increased likelihood of a dementia diagnosis. What’s more, they estimated that the EPA’s tightening of its PM2.5 regulation in 2005 may have averted 140,000 cases of dementia by 2013. Given the economic costs associated with dementia, the authors further estimated that stricter PM2.5 regulation during those years saved the country more than $160 billion as a result of reduced dementia rates.

Bear in mind, this analysis focused on just one of the health benefits of reducing air pollution-and only in older people.

The bigger picture: Thanks to increased federal air-quality regulation, U.S. deaths attributable to air pollution (mostly from PM2.5) dropped by nearly half between 1990 and 2010, from about 135,000 down to 71,000 deaths per year, despite increases in population and energy use, according to estimates in a study in Atmospheric Chemistry and Physics in October 2018. Rollbacks of clean-air regulations by the Trump administration would put such improvements at risk.

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