Air pollution in the first 2 years of life is associated with poor attention in later childhood

Children who are exposed to air pollution in utero or in the first two years of life may have poorer attention levels in later life, particularly in boys, researchers from the Barcelona Institute for Global Health (ISGlobal) have found. 

The researchers looked at exposure to nitrogen dioxide (NO2), a common pollutant that comes mainly from traffic emissions, finding that higher exposure to NO2 was associated with poorer attentional function in 4- to 6-year-olds, with increased susceptibility to this pollutant observed in the second year of life. 

This association persisted at an age of 6 to 8 years of age only in boys, with a slightly greater susceptibility period from birth to 2 years of age.

Researchers used data from 1,703 women and their children from the INMA Project birth cohorts in four Spanish regions. Using the home address, the researchers estimated daily residential exposure to NO2 during pregnancy and the first 6 years of childhood. 

In parallel, they assessed the attentional function (the ability to choose what to pay attention to and what to ignore) at 4-6 years and 6-8 years, and working memory (the ability to temporarily hold information) at 6-8 years, using validated computerised tests.

Key findings from the research include: 

• Higher exposure to NO2 between 1.3 and 1.6 years of age was associated with higher hit reaction time standard error, an indicator of speed consistency, in the attentional function test at 4–6 years of age.
• Higher exposure to NO2 between 1.5 and 2.2 years of age was associated with more omission errors.
• Higher exposure to NO2 between 0.3 and 2.2 years was associated with higher hit reaction time standard error at 6–8 years only in boys.
• No associations were found between higher exposure to NO2 and working memory in children aged 6 to 8 years.

“These findings underline the potential impact of increased traffic-related air pollution on delayed development of attentional capacity and highlight the importance of further research into the long-term effects of air pollution in older age groups”, co-author Anne-Claire Binter said. 

Attentional function is crucial for the development of the brain’s executive functions, which manage and control actions, thoughts and emotions to achieve a goal or purpose. 

“The prefrontal cortex, a part of the brain responsible for executive functions, develops slowly and it is still maturing during pregnancy and childhood,” Ms Binter added. 

“This makes it vulnerable to exposure to air pollution, which has been linked in animal studies to inflammation, oxidative stress, and impaired energy metabolism in the brain.”

“In boys, the association between exposure to N02 and attentional function may last longer because their brains mature more slowly, which could make them more vulnerable”, she continued. 

To understand this better, future studies should follow people over time to see how age and gender affect the relationship between air pollution and attention span, especially in older age groups.