Table 1.

Estimated effects of hypothetical air pollutant interventions on asthma incidence rates in the CHS, 1993 to 2014

Air pollutant intervention	Asthma incidence rate (95% CI)	Absolute incidence rate difference (95% CI)	Percentage incidence rate difference (95% CI)
NO2
Natural course	21.6 (19.6 to 23.3)	Reference	Reference
Remain at 1993 levels	25.8 (22.7 to 29.3)	4.2 (1.9 to 6.9)	19.3% (8.9% to 31.6%)
Percentage reduction
10%	19.4 (17.4 to 21.4)	−2.3 (−3.5 to −1.1)	−10.5% (−16.0% to −5.2%)
20%	17.4 (14.9 to 20.0)	−4.2 (−6.3 to −2.1)	−19.6% (−28.9% to −10.1%)
30%	15.7 (12.8 to 18.8)	−6.0 (−8.6 to −3.1)	−27.6% (−39.3% to −14.6%)
Hypothetical standards
30 ppb	20.1 (18.2 to 22.0)	−1.6 (−2.4 to −0.8)	−7.3% (−11.2% to −3.5%)
20 ppb	17.4 (15.2 to 19.9)	−4.2 (−5.9 to −2.3)	−19.6% (−27.0% to −10.7%)
10 ppb	13.2 (10.5 to 16.8)	−8.5 (−11.0 to −5.0)	−39.2% (−50.4% to −23.3%)
PM2.5
Natural course	21.6 (19.6 to 23.3)	Reference	Reference
Remain at 1993 levels	23.7 (20.9 to 26.8)	2.1 (0.2 to 4.4)	9.8% (0.9% to 20.4%)
Percentage reduction
10%	20.6 (18.6 to 22.7)	−1.0 (−1.9 to −0.1)	−4.5% (−8.9% to −0.4%)
20%	19.7 (17.3 to 22.2)	−1.9 (−3.6 to −0.2)	−8.8% (−16.8% to −0.9%)
30%	18.9 (16.0 to 21.9)	−2.8 (−5.2 to −0.3)	−12.8% (−23.9% to −1.3%)
Hypothetical standards
15 µg/m3	19.2 (16.7 to 21.9)	−2.4 (−4.3 to −0.2)	−11.0% (−20.1% to −1.2%)
12 µg/m3	18.4 (15.5 to 21.7)	−3.2 (−5.7 to −0.3)	−14.9% (−26.5% to −1.6%)
10 µg/m3	17.8 (14.6 to 21.5)	−3.8 (−6.6 to −0.4)	−17.6% (−30.7% to −1.9%)

Estimated incidence rates (cases per 1,000 person-years) and 95% CIs based on multilevel Poisson regression models with an offset term for person-time, a random effect for cohort nested within community, and adjusted for community, age, sex, ethnicity, race, presence of gas stove in the home, participation in team sports, and baseline year mean ambient temperature.