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Association of traffic-related air pollution with cognitive development in children
  1. Carmen Freire1,
  2. Rosa Ramos1,
  3. Raquel Puertas1,
  4. Maria-Jose Lopez-Espinosa1,2,
  5. Jordi Julvez3,
  6. Inmaculada Aguilera3,
  7. Francisco Cruz4,
  8. Mariana-Fatima Fernandez1,
  9. Jordi Sunyer3,5,
  10. Nicolas Olea1
  1. 1Laboratory of Medical Investigations, San Cecilio University Hospital, University of Granada, CIBER de Epidemiología y Salud Publica (CIBERESP), Granada, Spain
  2. 2Center for Research on Public Health (CSISP), Conselleria de Sanitat, Generalitat Valenciana, CIBER de Epidemiología y Salud Publica (CIBERESP), Valencia, Spain
  3. 3Centre for Research in Environmental Epidemiology (CREAL), Municipal Institute of Medical Research (IMIM-Hospital del Mar), Doctor Aiguader, Barcelona, CIBER de Epidemiología y Salud Publica (CIBERESP), Spain
  4. 4Department of Personality, Evaluation and Psychological Treatment, School of Psychology, University of Granada, Granada, Spain
  5. 5Universitat Pompeu Fabra (UPF), Doctor Aiguader, Barcelona, Spain
  1. Correspondence to Dr Carmen Freire, Laboratory of Medical Investigations, San Cecilio University Hospital, University of Granada, 18071 Granada, Spain; cfreire{at}


Background Air pollution from traffic has been associated with cardiorespiratory diseases in children and adults, but there is little information on its potential neurotoxic effects. This study aimed to investigate the association between exposure to nitrogen dioxide (NO2), as a marker of traffic-related air pollution, and cognitive development in children.

Methods A population-based birth cohort from southern Spain was followed from the age of 4 years for 1 year. Complete data for analyses were gathered on 210 children living in urban and rural areas. NO2 exposure was predicted by means of land use regression models. A standardised version of the McCarthy Scales of Children's Abilities (MSCA) was used to assess children's motor and cognitive abilities. Multivariate analyses were performed to evaluate the relation between exposure to NO2 and MSCA outcomes, adjusting for potential confounders.

Results A negative effect of NO2 was found across all MSCA subscales, despite low predicted NO2 exposure levels (5–36 μg/m3). Children exposed to higher NO2 (>24.75 μg/m3) showed a decrease of 4.19 points in the general cognitive score and decreases of 6.71, 7.37 and 8.61 points in quantitative, working memory and gross motor areas, respectively. However, except for gross motor function, associations were not statistically significant.

Conclusion Although results were not statistically significant, the associations found between exposure to NO2 and cognitive functions suggest that traffic-related air pollution may have an adverse effect on neurodevelopment, especially early in life, even at low exposure levels.

  • air pollution
  • children
  • cognitive development
  • land use regression
  • neuroepidemiology
  • traffic-related air pollution

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  • Funding Consejería de Salud de la Junta de Andalucía (SAS 07/0133), the Spanish Ministry of Health (FIS 07/0252), Spanish Ministry of Science and Innovation (FPU-Programme to CF; Juan de la Cierva Programme-FSE to MJLE) and the European Commission (CONTAMED FP7-ENV-212502).

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Ethics Committee of the San Cecilio University Hospital of Granada (Spain).

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.