Air pollution exposure may lead to lower cognitive performance, study indicates

Written by Sharon Salt, Editor

A landmark study from an International Food Policy Research Institute (IFPRI; Washington DC, USA) scientist has established that exposure to air pollution over a long period of time significantly impacts cognitive abilities, as measured through steep reduction in verbal and math test scores.
“Long-term exposure to air pollution impedes cognitive performance in verbal and math tests,” commented Xiaobo Zhang, Senior Research Fellow at IFPRI. “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.

In this study, published in the Proceedings of the National Academy of Sciences, the sample size consisted of approximately 32,000 individuals. The researchers 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.

The findings indicated that both verbal and math scores decreased with increasing cumulative air pollution exposure; with a steeper decline for verbal scores than math scores. In addition to this, the decline in verbal score was more pronounced among males than females. Among males, the decline in verbal scores was reported to be 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,” concluded Zhang.

The researchers have estimated that reducing fine particulate matter concentrations to the US Environmental Protection Agency standard (50 µg/m3) would increase verbal and math scores by 2.41 and 0.39 points, respectively, which is equivalent to an increase from the median to the 63rd and 58th percentiles, respectively.

Zhang also mentioned that these research findings shed light on other developing countries. Accordingly to the WHO, the world’s top 20 most-polluted cities are in developing countries. Almost all the cities in low- and middle-income countries with more than 1,000,000 residents fail to meet WHO air quality guidelines.

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Sources: Zhang X, Chen X, Zhang X. The impact of exposure to air pollution on cognitive performance. Proc. Natl Acad. Sci. doi:10.1073/pnas.1809474115 (2018) (Epub ahead of print); www.ifpri.org/news-release/new-study-exposure-air-pollution-leads-lower-verbal-math-test-scores