Association between traffic-related air pollution in schools and cognitive development in primary school children: a prospective cohort study

• Published in: PLoS medicine Vol. 12; no. 3; p. e1001792
• Main Authors: Sunyer, Jordi, Esnaola, Mikel, Alvarez-Pedrerol, Mar, Forns, Joan, Rivas, Ioar, López-Vicente, Mònica, Suades-González, Elisabet, Foraster, Maria, Garcia-Esteban, Raquel, Basagaña, Xavier, Viana, Mar, Cirach, Marta, Moreno, Teresa, Alastuey, Andrés, Sebastian-Galles, Núria, Nieuwenhuijsen, Mark, Querol, Xavier
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.03.2015; Public Library of Science (PLoS)
• Subjects: Air Pollutants - adverse effects; Air Pollutants - analysis; Air pollution; Air Pollution - adverse effects; Air Pollution - analysis; Air Pollution, Indoor - adverse effects; Air Pollution, Indoor - analysis; Aire; Attention - drug effects; Brain - drug effects; Brain - growth & development; Carbon - adverse effects; Carbon - analysis; Child; Child development; Child Development - drug effects; Cognition; Cognition - drug effects; Contaminació; Desenvolupament; Elementary school students; Environmental Exposure - adverse effects; Environmental Exposure - analysis; Experiments; Female; Health aspects; Humans; Infants; Male; Memory; Memory - drug effects; Motor Vehicles; Nitrogen dioxide; Nitrogen Dioxide - adverse effects; Nitrogen Dioxide - analysis; Particle Size; Particulate Matter - adverse effects; Particulate Matter - analysis; Pollutants; Prospective Studies; Schools; Social Class; Social classes; Socioeconomic factors; Spain; Vehicle Emissions; Spain; Spain, Cataluna, Barcelona
• ISSN: 1549-1676; 1549-1277; 1549-1676
• DOI: 10.1371/journal.pmed.1001792

Air pollution is a suspected developmental neurotoxicant. Many schools are located in close proximity to busy roads, and traffic air pollution peaks when children are at school. We aimed to assess whether exposure of children in primary school to traffic-related air pollutants is associated with impaired cognitive development. We conducted a prospective study of children (n = 2,715, aged 7 to 10 y) from 39 schools in Barcelona (Catalonia, Spain) exposed to high and low traffic-related air pollution, paired by school socioeconomic index; children were tested four times (i.e., to assess the 12-mo developmental trajectories) via computerized tests (n = 10,112). Chronic traffic air pollution (elemental carbon [EC], nitrogen dioxide [NO2], and ultrafine particle number [UFP; 10-700 nm]) was measured twice during 1-wk campaigns both in the courtyard (outdoor) and inside the classroom (indoor) simultaneously in each school pair. Cognitive development was assessed with the n-back and the attentional network tests, in particular, working memory (two-back detectability), superior working memory (three-back detectability), and inattentiveness (hit reaction time standard error). Linear mixed effects models were adjusted for age, sex, maternal education, socioeconomic status, and air pollution exposure at home. Children from highly polluted schools had a smaller growth in cognitive development than children from the paired lowly polluted schools, both in crude and adjusted models (e.g., 7.4% [95% CI 5.6%-8.8%] versus 11.5% [95% CI 8.9%-12.5%] improvement in working memory, p = 0.0024). Cogently, children attending schools with higher levels of EC, NO2, and UFP both indoors and outdoors experienced substantially smaller growth in all the cognitive measurements; for example, a change from the first to the fourth quartile in indoor EC reduced the gain in working memory by 13.0% (95% CI 4.2%-23.1%). Residual confounding for social class could not be discarded completely; however, the associations remained in stratified analyses (e.g., for type of school or high-/low-polluted area) and after additional adjustments (e.g., for commuting, educational quality, or smoking at home), contradicting a potential residual confounding explanation. Children attending schools with higher traffic-related air pollution had a smaller improvement in cognitive development.