A huge medical study involving 50,000 people has discovered that long-term exposure to air pollution leads to a massive reduction in intelligence, and can impair even simple math solving skills.
The collaborative study by researchers from Beijing Normal University and Yale University also found that air pollution, especially those infused by a deadly microscopic pollutant called "PM2.5," might be more damaging to the human brain than originally thought. Air pollution also causes cognitive impairment especially in the elderly.
The study was led by Xin Zhang of Beijing Normal University and Xi Chen of Yale University was conducted in 2010 and again in 2014. The researchers recorded the time, date, location, and matched tests results to air quality data in their effort to find a link between poor air quality and a decline in cognitive skills.
The results were startling. Researchers found that pollution can affect a person's ability to think in verbal and math tests, which was unexpected. Damage to the brain is more severe in older men and in men with no education beyond primary school.
Long-term exposure to air pollution impedes cognitive performance in verbal and math tests, said Zhang Xiaobo, chair professor of economics at Peking University, and one of the study's authors.
He pointed out that the damage to cognitive ability by air pollution likely impedes the development of human capital. Zhang said their findings on the damaging effect of air pollution on cognition imply that the indirect effect of pollution on social welfare could be much larger than previously thought.
Cumulative and increasing exposure to air pollution decreased both verbal and math scores. There was also a steeper decline for verbal scores than math scores. The study showed the drop in verbal scores was larger among males than females.
Among males, the drop in verbal scores was more pronounced with age. This age dependence was more significant in those with less than a middle school education compared with a middle school education or more.
The study said the damage air pollution has on aging brains likely causes significant health and economic costs since cognitive functioning is critical for the elderly in their daily routines and making high-important economic decisions. This finding has important policy implications, said Zhang.
Reducing fine particulate matter concentrations to the US Environmental Protection Agency (EPA) standard of 50 μg/m3 should increase verbal and math scores by 2.41 and 0.39 points, respectively.
The study is a wake-up call for developing countries that house the majority of the world's worst polluted cities. A recent study from the World Health Organization (WHO) found that the world's top 20 most polluted cities are in developing countries.
