Breathing in bad air may lead to attention problems in children

Increased exposure to nitrogen dioxide (NO₂) in the first 2 years of life has been linked to poor attention capacity in childhood.

In a study conducted in Spain, children with higher NO₂ exposure between 1.3 and 1.6 years of age performed with a higher hit reaction time standard error (HRT-SE) in the attentional function test conducted at age 4–6 years (0.14 ms per 10 μg/m³ increase in NO₂, 95 percent confidence interval [CI], 0.05–0.22). [Environ Int 2024;doi:10.1016/j.envint.2024.108604]

Additionally, those with higher NO₂ exposure between 1.5 and 2.2 years of age had more omission errors in test (1.02 per 10 μg/m³ increase in NO₂, 95 percent CI, 1.01–1.03).

In further analysis stratifying by sex and correcting for multiple testing, the association between higher exposure to NO₂ between 0.3 and 2.2 years and higher HRT-SE at age 6–8 years appeared to be evident only among boys (10.61 ms per 10 μg/m³ increase in NO₂, 95 percent CI, 3.46–17.75).

Air pollution exposure had no effect on children’s working memory at 6–8 years.

“These findings underline the potential impact of increased traffic-related air pollution on delayed development of attentional capacity [as well as] the importance of further research into the long-term effects of air pollution in older age groups,” said senior study author Dr Anne-Claire Binter, an environmental epidemiologist at the Barcelona Institute for Global Health (ISGlobal), Barcelona, Spain.

According to Binter, attentional function is crucial for the development of the brain’s executive functions—a range of cognitive processes (eg, planning, critical thinking, and inhibitory control, among others) that lays the foundation for a child’s ability to learn. And the first decade of life is prime time for this development. [Int J Environ Res Public Health 2022;19:749]

The development of the part of the brain responsible for executive functions, the prefrontal cortex, is a prolonged process extending from pregnancy to childhood. Binter pointed out that this ongoing development increases susceptibility to environmental factors such as air pollution, which has been shown to trigger inflammation, oxidative stress, and impaired energy metabolism in the brain. [Psychol Bull 2008;134:31-60]

“In boys, the association between exposure to NO₂ and attentional function may last longer because their brains mature more slowly, which could make them more vulnerable,” she said.

The takeaway is that “early childhood, up to the age of 2 [years], seems to be a relevant period for implementing preventive measures. Even a small effect at the individual level from relatively low levels of exposure, as in this study, can have large consequences at the population level,” Binter noted. “Exposure to traffic-related air pollution is therefore a determinant of the health of future generations.”

The study population comprised 1,703 women and their children from the INMA Project birth cohorts in four Spanish regions. Binter and colleagues estimated daily residential exposure to NO₂ during pregnancy and the first 6 years of childhood using land use regression models. Attentional function was assessed at 4–6 years and 6–8 years using the Conners Kiddie Continuous Performance Test and the Attention Network Test, respectively, and working memory at 6–8 years, using the N-back task.