Research

Traffic-related air pollution and respiratory symptoms among asthmatic children, resident in Mexico City: the EVA cohort study

Maria-Consuelo Escamilla-Nuñez¹ , Albino Barraza-Villarreal¹ , Leticia Hernandez-Cadena¹ , Hortensia Moreno-Macias¹ , Matiana Ramirez-Aguilar² , Juan-Jose Sienra-Monge³ , Marlene Cortez-Lugo¹ , Jose-Luis Texcalac¹ , Blanca del Rio-Navarro³ and Isabelle Romieu¹

¹  Instituto Nacional de Salud Pública, Mexico

²  Comision Federal para la Proteccion contra Riesgos Sanitarios, SSA, Mexico

³  Hospital Infantil de Mexico Federico Gomez, Mexico

author email corresponding author email

Respiratory Research 2008, 9:74doi:10.1186/1465-9921-9-74

Published:	16 November 2008

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 μg/m³ (IQR) of PM_2.5 (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% to16.4%) 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).

Conclusion

Respiratory symptoms in asthmatic children were significantly associated with exposure to traffic exhaust, especially from natural gas and diesel-fueled vehicles.