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


RESULTS
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.


CONCLUSIONS
Children attending schools with higher traffic-related air pollution had a smaller improvement in cognitive development.
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain; Institut Hospital del Mar d'Investigacions Mèdiques-Parc de Salut Mar, Barcelona, Catalonia, Spain.
Jordi
J
Sunyer
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Mikel
M
Esnaola
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Mar
M
Alvarez-Pedrerol
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Joan
J
Forns
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain; Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain.
Ioar
I
Rivas
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Mònica
M
López-Vicente
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain; Learning Disabilities Unit (UTAE), Neuropediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Barcelona, Spain.
Elisabet
E
Suades-González
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Maria
M
Foraster
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Raquel
R
Garcia-Esteban
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Xavier
X
Basagaña
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain.
Mar
M
Viana
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Marta
M
Cirach
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain.
Teresa
T
Moreno
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain.
Andrés
A
Alastuey
Pompeu Fabra University, Barcelona, Catalonia, Spain.
Núria
N
Sebastian-Galles
Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Catalonia, Spain; Pompeu Fabra University, Barcelona, Catalonia, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Madrid, Spain.
Mark
M
Nieuwenhuijsen
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Catalonia, Spain.
Xavier
X
Querol
D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D016902:Air Pollution, Indoor / Q000009:adverse effects / Q000032:analysis; D001288:Attention / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000254:growth & development; D002244:Carbon / Q000009:adverse effects / Q000032:analysis; D002648:Child; D002657:Child Development / Q000187:drug effects*; D003071:Cognition / Q000187:drug effects*; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects; D018986:Motor Vehicles; D009585:Nitrogen Dioxide / Q000009:adverse effects / Q000032:analysis; D010316:Particle Size; D052638:Particulate Matter / Q000009:adverse effects / Q000032:analysis; D011446:Prospective Studies; D012574:Schools; D012923:Social Class; D013030:Spain; D001335:Vehicle Emissions
D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions; D002244:Carbon; D009585:Nitrogen Dioxide