The association between cognitive performance and exposure to particulate air pollution in primary schoolchildren

Abstract

Cardiorespiratory effects and mechanisms of particulate air pollution have been largely investigated and an association with adverse outcomes has been well established. However, little is known regarding neurobehavioral effects. Studies in animals suggest a biological plausability for a link between ultrafine particles (UFP) and neurological impairment. However, information based on studies in humans is very limited. Objectives: In a panel of primary schoolchildren, the effect of chronic and acute exposure to fine and ultrafine particulate air pollution on cognitive performance was investigated. Methods: 70 children, aged 9 to 12 years, were recruited at a primary school in Flanders, Belgium. A series of computerized tests from the Neurobehavioral Evaluation System (NES) battery and the Stroop test were used to evaluate cognitive performance. Acute exposure to particulate matter and UFP was monitored on site. chronic exposure was estimated based on the proximity between the place of residence and major roads. The change in cognitive test outcome associated with exposure to UFP was estimated using mixed models, taking the clustering of the data into account. Results: A significant association was found between attention tests and acute as well as chronic exposure to air pollution. An interquartile range increase in indoor UFP was associated with a 5.44% (1.01 to 9.87) delay in response reaction time of the Stroop test. A doubling in the distance to major roads resulted in an estimated reduction in reaction time of -1.34% (-2.30 to -0.38). Indoor UFP was also significantly associated with the outcome of the Continuous Performance test, with an estimated percent change in mean reaction time of 1.00% (0.23 to 1.77), but not with distance to major roads. Similar associations were found with outdoor UFP. None of the other tests from the NES battery showed a significant association with exposure to particulate air pollution and no significant associations were found with other particulate matter fractions (TSP, PM10 or PM2.5). The reported associations were independent of age, gender, test session number, hour of the day, BMI, maximum outdoor apparent temperature, exposure to environmental tobacco smoke, birth weight, breast feeding, and educational level of the mother. Conclusion: Both acute and chronic exposure to air pollution, as implemented by residential distance to major roads, are associated with an inverse effect on children's attention.