title: Traffic-related air pollution and respiratory symptoms among asthmatic children, resident in Mexico City: the EVA cohort study.
abstract: BACKGROUND
  Taffic-related air pollution has been related to adverse respiratory outcomes; however, there is still uncertainty concerning the type of vehicle emission causing most deleterious effects.
  
  
  METHODS
  A panel study was conducted among 147 asthmatic and 50 healthy children, who were followed up for an average of 22 weeks. Incidence density of coughing, wheezing and breathing difficulty was assessed by referring to daily records of symptoms and child's medication. The association between exposure to pollutants and occurrence of symptoms was evaluated using mixed-effect models with binary response and poisson regression.
  
  
  RESULTS
  Wheezing was found to relate significantly to air pollutants: an increase of 17.4 microg/m3 (IQR) of PM2.5 (24-h average) was associated with an 8.8% increase (95% CI: 2.4% to 15.5%); an increase of 34 ppb (IQR) of NO2 (1-h maximum) was associated with an 9.1% increase (95% CI: 2.3% to 16.4%) and an increase of 48 ppb (IQR) in O3 levels (1 hr maximum) to an increase of 10% (95% CI: 3.2% to 17.3%). Diesel-fueled motor vehicles were significantly associated with wheezing and bronchodilator use (IRR = 1.29; 95% CI: 1.03 to 1.62, and IRR = 1.32; 95% CI: 0.99 to 1.77, respectively, for an increase of 130 vehicles hourly, above the 24-hour average).
  
  
  CONCLUSIONS
  Respiratory symptoms in asthmatic children were significantly associated with exposure to traffic exhaust, especially from natural gas and diesel-fueled vehicles.
authors.affiliation: Instituto Nacional de Salud Pública, Mexico. mescamilla@correo.insp.mx
authors.forename: Maria-Consuelo
authors.initials: MC
authors.lastname: Escamilla-Nuñez
authors.forename: Albino
authors.initials: A
authors.lastname: Barraza-Villarreal
authors.forename: Leticia
authors.initials: L
authors.lastname: Hernandez-Cadena
authors.forename: Hortensia
authors.initials: H
authors.lastname: Moreno-Macias
authors.forename: Matiana
authors.initials: M
authors.lastname: Ramirez-Aguilar
authors.forename: Juan-Jose
authors.initials: JJ
authors.lastname: Sienra-Monge
authors.forename: Marlene
authors.initials: M
authors.lastname: Cortez-Lugo
authors.forename: Jose-Luis
authors.initials: JL
authors.lastname: Texcalac
authors.forename: Blanca
authors.initials: B
authors.lastname: del Rio-Navarro
authors.forename: Isabelle
authors.initials: I
authors.lastname: Romieu
mesh_terms: D000397:Air Pollution / Q000032:analysis* / Q000706:statistics & numerical data*; D001249:Asthma / Q000453:epidemiology*; D002648:Child; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D015995:Prevalence; D012120:Respiration Disorders / Q000453:epidemiology*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D001335:Vehicle Emissions