Pollution directly affects children under 2 years old

A study by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, highlights the possible impact of traffic-related air pollution (NO2) on the attentional development of the youngest children. 

A growing body of research shows that exposure to air pollution, especially during pregnancy and infancy, can have a negative impact on brain development. Now, a study led by the Barcelona Institute for Global Health (ISGlobal), a centre supported by the "la Caixa" Foundation, has found that exposure to nitrogen dioxide (NO2) during the first two years of life is associated with reduced attention span in children aged 4 to 8 years, especially boys. NO2 is a pollutant from traffic emissions. 

The study, published in Environment International, associated higher exposure to NO2 with poorer attention span in children aged 4-6 years, and found increased susceptibility to this pollutant in the second year of life. This association persisted from 6 to 8 years only in boys, not in girls, with a somewhat longer period of susceptibility to NO2 at birth at two years of age. 

The research team used data from 1,703 women and their children from the INMA Project birth cohorts in four Spanish regions. From the address of residence, the team estimated the daily exposure to NO2 during pregnancy and in the first 6 years of childhood. In parallel, attentional function (the ability to choose what to pay attention to and what to ignore) at 4-6 years and at 6-8 years, and working memory (the ability to temporarily retain information) at 6-8 years were assessed using validated computerised tests.

Periods of increased susceptibility to environmental contamination 

A previous INMA study had found that exposure to NO2 during pregnancy and infancy was associated with impaired attentional function in children aged 4-5 years. The present study found that: 

Higher exposure to NO2 between 1.3 and 1.6 years was associated with higher standard error of stimulus reaction time, an indicator of consistency of response speed, on the test of attentional function at 4-6 years. 

Higher exposure to NO2 between 1.5 and 2.2 years was associated with a higher number of omission errors. 

Higher NO2 exposure between 0.3 and 2.2 years was associated with higher reaction time standard error at 6-8 years only in boys. 

On the other hand, no associations were found between higher NO2 exposure and working memory in boys and girls aged 6-8 years. 

"These findings underline the potential impact of traffic-related air pollution on the delayed development of attentional capacity, and the importance of further investigating its long-term effects in older age groups", explains Anne-Claire Binter, last author of the study and postdoctoral researcher at ISGlobal.

As the brain matures

Attentional function is crucial for the development of the brain's executive functions, which manage and control the actions, thoughts and emotions that enable us to achieve a goal or purpose. "The prefrontal cortex, the part of the brain responsible for executive functions, develops slowly and matures during pregnancy and childhood," adds Binter. 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 NO2 exposure and attentional function may last longer because their brains mature more slowly, which could make them more vulnerable," she says. To understand this better, people should be followed up to see how age and gender affect the relationship between air pollution and attention span, especially in older age groups. In conclusion, "this study suggests that early childhood, up to the age of two, seems a relevant period for preventive measures," says Binter. "Even a small effect at the

individual level of relatively low levels of exposure, as in this study, can have large consequences at the population level. Exposure to traffic-related air pollution is therefore a determinant for the health of future generations". 

Referencia 

Crooijmans, K.L.H.A., Iñiguez, C., Withworth, K.W., Estarlich, M., Lertxundi, A., Fernández-Somoano, A., Tardón, A., Ibarluzea, J., Sunyer, J., Guxens M., Binter, A.C. 2024, Nitrogen dioxide exposure, attentional function, and working memory in children from 4 to 8 years: Periods of susceptibility from pregnancy to childhood, Environment International. Volume 186, 2024, 108604, ISSN 0160-4120, https://doi.org/10.1016/j.envint.2024.108604 

Sobre ISGlobal 

The Barcelona Institute for Global Health (ISGlobal) is the result of an innovative alliance between the "la Caixa" Foundation and academic and governmental institutions to contribute to the efforts of the international community to address the challenges of health in a globalised world. ISGlobal consolidates a node of excellence based on research and medical care that originates in the hospital (Hospital Clínic and Parc de Salut MAR) and academic (University of Barcelona and Pompeu Fabra University) spheres. Its working model is based on the generation of scientific knowledge through Research Programmes and Groups, and its translation through the areas of Training and Analysis and Global Development. ISGlobal is accredited as a "Severo Ochoa Centre of Excellence" and is a member of the CERCA system of the Generalitat de Catalunya.