Table 4.

Associations Between Binary Exposure to PM_2.5 and Censoring^a and Incident IHD Hazard Ratios for Binary Exposure Based on Cox Marginal Structural Models With and Without Censoring Weights^b in a Cohort of Actively Employed US Aluminum Workers Stratified by Facility Type, 1998–2012

Definition of Censoring Used to Create Weights, by Facility Type	Probability of Remaining Uncensored Associated With Exposure to PM2.5		Risk of IHD Associated With Exposure to PM2.5
	OR	95% CI	HR	95% CI
No censoring weights
Smelting			1.98	1.18, 3.32
Fabrication			1.38	0.98, 1.94
All terminationsc
Smelting	1.07	0.95, 1.20	1.87	1.10, 3.18
Fabrication	1.05	0.94, 1.16	1.35	0.95, 1.91
<55 Years of age at terminationd
Smelting	1.11	0.96, 1.28	1.96	1.17, 3.29
Fabrication	0.92	0.81, 1.05	1.36	0.97, 1.91
<55 Years of age and not laid off, transferred to salary, or having lost claims eligibilitye
Smelting	1.25	1.05, 1.48	1.95	1.17, 3.27
Fabrication	1.09	0.92, 1.30	1.37	0.97, 1.93

Abbreviations: CI, confidence interval; HR, hazard ratio; IHD, ischemic heart disease; OR, odds ratio; PM_2.5, particulate matter with aerodynamic diameter of 2.5 μm or less.

^a From logistic models for the probability of remaining uncensored, including covariates for sex, race, smoking status, body mass index (weight (kg)/height (m)²), job grade, plant, and risk score.

^b Hazard ratio comparing those always exposed above with those always exposed below the 10th percentile of PM_2.5 cutoff.

^c A total of 2,641 workers in smelting facilities and 3,707 workers in fabrication facilities were considered censored.

^d A total of 1,446 workers in smelting facilities and 2,210 workers in fabrication facilities were considered censored.

^e A total of 956 workers in smelting facilities and 1,178 workers in fabrication facilities were considered censored.