Traffic-related air pollution and respiratory symptoms among asthmatic children, resident in Mexico City: the EVA cohort study.
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.
Escamilla-Nuñez
Maria-Consuelo
MC
Instituto Nacional de Salud Pública, Mexico. mescamilla@correo.insp.mx
Barraza-Villarreal
Albino
A
Hernandez-Cadena
Leticia
L
Moreno-Macias
Hortensia
H
Ramirez-Aguilar
Matiana
M
Sienra-Monge
Juan-Jose
JJ
Cortez-Lugo
Marlene
M
Texcalac
Jose-Luis
JL
del Rio-Navarro
Blanca
B
Romieu
Isabelle
I
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*
D001335:Vehicle Emissions