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

Table 4 Effect of traffic on the risk of respiratory symptoms and bronchodilator use among asthmatic children

Type of vehicle*		Coughing	Wheezing	Use of Bronchodilator
	IQR	IRR 95% CI+	IRR 95% CI	IRR 95% CI
A	1,537	1.17(0.87, 1.58)	1.46(0.99, 2.14)	1.64(1.01, 2.66)
B	499	1.37(0.95, 1.97)	1.80(1.12, 2.88)	1.99(1.10, 3.61)
C	130	1.15(0.97, 1.36)	1.29(1.03, 1.62)	1.32(0.99, 1.77)
Distance from main avenue to the child's residence (meters)	212	0.87(0.68, 1.11)	0.69(0.49, 0.98)	0.68(0.42, 1.08)

* Hourly average. Definition: A: Private cars (Gasoline); B: Small buses for public transportation (Gasoline or natural gas); C: School buses, other buses, pick up trucks and heavy trucks (Diesel). Poisson models are adjusted by sex, severity of asthma, atopy and the distance between the traffic road and the child's residence (this last variable is not considered in the distance model).
+ Coefficients were calculated by a change of an interquartile range (IQR).

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