Table 3.

Risk of asthma symptoms per 20-ppb increase in NO₂ exposure.

	Unadjusted		Adjusteda		Adjustedb
Symptom	IRR	95% CI	IRR	95% CI	IRR	95% CI
Daytime wheezing, coughing, or chest tightness	1.05	0.99–1.12	1.03	0.96–1.11	1.04	0.97–1.12
Slowing activity due to asthma, wheeze, chest tightness, or cough	1.07	1.00–1.14*	1.06	0.99–1.14	1.08	0.94–1.15
Limited speech due to wheeze	1.12	1.04–1.21**	1.15	1.05–1.25**	1.17	1.08–1.27**
Wheeze, cough, or chest tightness while running	1.08	1.01–1.15*	1.07	0.99–1.14	1.09	1.01–1.17*
Coughing without a cold	1.13	1.06–1.20#	1.10	1.02–1.18**	1.15	1.07–1.23#
Nocturnal awakenings due to cough, wheeze, shortness of breath, or chest tightness	1.11	1.04–1.18#	1.09	1.02–1.16*	1.12	1.04–1.19**

^aModels are adjusted for PM_2.5; SHS; season of sampling; age, sex, and race of the child; and mother’s education level.

^bModels are adjusted for PM_2.5; SHS; distance from the curb, type of street in front of home, season of sampling; age, sex, and race of the child; and mother’s education level.

^*p < 0.05.

^**p < 0.01.

^#p < 0.001.