Table 2. Incidence rate ratios (hazard ratios) for incidence of physician-diagnosed obstructive airway disease (OAD) as a function of exposure intensity for the three periods identified as the times of rate ratio change that best fit the data.

The analysis controls for age on 9/11, retirement status (time dependent), smoking status (ever vs. never), and implicitly for seasonality (by quarter).

Period	Exposure Contrast	Any OAD Rate Ratio (95% CI)	Asthma Rate Ratio (95% CI)	Non-Asthma OAD Rate Ratio (95% CI)
	High vs. Low	4.02 (2.62,6.16)	4.47 (2.48, 8.06)	3.56 (1.91, 6.66)
	High vs. Moderate	2.11 (1.71,2.61)	2.05 (1.56, 2.70)	2.21 (1.60, 3.07)
	Moderate vs. Low	1.90 (1.26,2.86)	2.18 (1.24, 3.84)	1.61 (0.89, 2.92)
15-84 months	High vs. Low	1.90 (1.49,2.44)	2.02 (1.47, 2.77)	1.74 (1.17, 2.59)
	High vs. Moderate	1.20 (1.03,1.39)	1.28 (1.06, 1.56)	1.06 (0.83, 1.36)
	Moderate vs. Low	1.59 (1.28,1.98)	1.57 (1.19, 2.08)	1.64 (1.16, 2.32)
85-120 months	High vs. Low	1.20 (0.92,1.56)	1.36 (0.93,1.99)	1.03 (0.71, 1.51)
	High vs. Moderate	1.17 (0.97,1.42)	1.21 (0.92,1.58)	1.14 (0.86, 1.51)
	Moderate vs. Low	1.02 (0.82,1.27)	1.13 (0.82,1.55)	0.91 (0.67,1.23)