A new Spanish study adds to the growing body of evidence suggesting that air pollution exposure in early childhood may be linked to cognitive dysfunction.
Researchers from Barcelona Institute for Global Health (ISGlobal) discovered that children who were exposed to small particulate matter in the womb and during the first years of life were at greater risk of poorer working memory (link appeared in boys only) and reduced executive attention (in both boys and girls).
The objective of the study, which was conducted as part of the BREATHE project, was to build on the knowledge generated by previous research from the same team, which found lower levels of cognitive development in children attending schools with higher levels of traffic-related air pollution.
The research, published in the journal Environmental Health Perspectives, involved 2,221 children (ages 7 to 10) attending schools in the city of Barcelona. The children’s cognitive abilities were evaluated via various computerized tests. Exposure to air pollution at home during pregnancy and throughout childhood was estimated with a mathematical model using real measurements.
The researchers found that greater PM2.5 (particulate matter with a diameter of less than 2.5 μm) exposure from pregnancy until age 7 years was associated with lower working memory scores on cognitive tests taken between the ages of 7 and 10 years — but only in boys. Working memory is responsible for temporarily holding information for further use. It plays a fundamental role in learning, reasoning, problem-solving and language comprehension.
“As yet, we don’t understand what causes these differences, but there are various hormonal and genetic mechanisms that could lead to girls having a better response to inflammatory processes triggered by fine particulate matter and being less susceptible to the toxicity of these particles,” commented Ioar Rivas, ISGlobal researcher and lead author of the study.
The findings suggest that exposure to fine particulate matter throughout the study period had a cumulative effect, although the associations were stronger when the most recent years of exposure were taken into account.
The study also found that higher exposure to particulate matter was associated with a reduction in executive attention in both boys and girls. Executive attention is one of the three networks that make up a person’s attention capacity. It is involved in high-level forms of attention, error detection, response inhibition, and the regulation of thoughts and feelings.
Whereas previous studies in the BREATHE project analyzed exposure to air pollution at schools over the course of a year, this study assessed exposures at the participants’ homes over a much longer time: from the prenatal period to 7 years of age.
“This study reinforces our previous findings and confirms that exposure to air pollution at the beginning of life and throughout childhood is a threat to neurodevelopment and an obstacle that prevents children from reaching their full potential,” said Jordi Sunyer, Childhood and Environment Programme Coordinator at ISGlobal and last author of the study.