Table 6

Regression coefficients and risk estimates of dying for lung cancer by smoking, airflow obstruction, cumulative exposure to radon daughters and silica (continuous variables) and by ILO radiological categories of silicosis (categorical variable) based on the Cox's multiple regression analysis of 665 silicotics with available spirometry (34 lung cancer deaths)

Variables	β^6-150	SE	p Value		RR^6-151	95% CI
Smoking (cigarettes/day)	0.0468	0.0202	0.0208	RR per 10 cigarettes/day	1.60	1.07 to 2.37
Airflow obstruction (FEV₁/VC−predicted)×100	0.0491	0.0125	0.0001	RR per 20% below predicted	2.67	1.63 to 4.36
Radon daughters exposure (WLM)	0.0037	0.0014	0.0112	RR per 100 WLM	1.45	1.10 to 1.90
Cumulative exposure to respirable SiO₂(gh/m³)^6-152	0.0026	0.0412	0.9491	RR per 10 gh/m³	1.03	0.46 to 2.30
Severity of radiological silicosis	0.0259	0.2281	0.9093
(ILO category)^6-152 ^6-153				RR for category 1/0–1/2	1.00
				RR for category 2/1–2/3	1.03	0.66 to 1.61
				RR for category 3/2+	1.05	0.43 to 2.57

↵6-150 β=regression coefficient.
↵6-151 RR=relative risk.
↵6-152 Variables that did not enter the stepwise model.
↵6-153 Categorical variable included as 0, 1, 2.