Recent studies have shown that air pollution is bad for health. But how bad is it? A four-year longitudinal study by the International Food Policy Research Institute (IFPRI) has, for the first time, found that exposure to air pollution over a significant period of time impacts cognitive abilities, and leads to steep reduction in verbal and math tests scores.

“Long-term exposure to air pollution impedes cognitive performance in verbal and math tests,” said study author Xiaobo Zhang, senior research fellow, IFPRI and distinguished chair professor of economics at Peking University .

“The damage on cognitive ability by air pollution also likely impedes the development of human capital. Therefore, a narrow focus on the negative effect on health may underestimate the total cost of air pollution. Our 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,” Zhang added.

While the health consequences of air pollution are well known, few studies have examined its impact on cognitive abilities.

The study, “The impact of exposure to air pollution on cognitive performance”, co-authored by IFPRI’s Xiaobo Zhang, Xin Zhang of Beijing Normal University , and Xi Chen of Yale University, has been published in health journal Proceedings of the National Academy of Sciences (PNAS).

The study, with a sample size of nearly 32,000, examined the relationship between cognitive test scores, taken from the nationally representative China Family Panel Studies longitudinal survey conducted in 2010 and 2014, with short- and long-term air pollution exposure calculated from official air pollution index values. Zhang observed that the impact for India could be much worse as pollution levels are higher in New Delhi than Beijing.

Both verbal and math scores decreased with increasing cumulative air pollution exposure, with a steeper decline for verbal scores than math scores, according to the key findings of the study. The decline in verbal scores was more pronounced among males (49% more) than females. Among males, the decline in verbal scores became more pronounced with age, and this age dependence was greater in those with less than a middle school education compared with a middle school education or more.

“The damage air pollution has on aging brains likely imposes substantial health and economic cost, considering that cognitive functioning is critical for the elderly to both running daily errands and making high-stakes economic decisions. This finding has been neglected in the policy discourse, and has important policy implications,” said Zhang. Cognitive decline or impairment are risk factors of Alzheimer’s disease and other forms of dementia for the elderly.

“These research findings on China, the largest developing country with severe air pollution, also shed light on other developing countries,” said Zhang. World’s top 20 most polluted cities, according to the World Health Organization ’s (WHO) database, are in developing countries. Almost all the cities in low- and middle-income countries with more than 1,00,000 residents fail to meet WHO air quality guidelines.

