Table 5.

Incidence rate ratios (IRR) and 95% CIs for lung cancer related to log-transformed cumulative exposure to cristobalite, SiC fibres and SiC particles among 1166 male ever-smoking Norwegian long-term SiC industry workers employed during 1913–2003 and followed up during 1953–2008, adjusted for age and the other exposure factors

	Smokers, N=1166, 30714 PYR, 58 cases
	IRR	95% CI	LR-test*	AIC	rPearson†
Cristobalite	1.9	1.2 to 2.9		275.6
Cristobalite adjusted for SiC	2.0	1.2 to 3.3	p=0.8	277.5	0.74
Cristobalite adjusted for SiC and fibres	1.6	0.8 to 3.3	p=0.4	278.8
Cristobalite adjusted for fibres	1.5	0.8 to 2.9	p=0.4	276.9	0.76
Cristobalite adjusted for fibres and SiC	1.6	0.8 to 3.3	p=0.8	278.8
Fibres	1.9	1.2 to 2.9		276.7
Fibres adjusted for SiC	1.7	1.1 to 2.9	p=0.6	278.4	0.51
Fibres adjusted for SiC and cristobalite	1.3	0.7 to 2.6	p=0.2	278.8
Fibres adjusted for cristobalite	1.3	0.7 to 2.6	p=0.2	276.9	0.76
Fibres adjusted for cristobalite and SiC	1.3	0.7 to 2.6	p=0.8	278.8
SiC	1.4	1.0 to 2.1		281.4
SiC adjusted for fibres	1.1	0.7 to 1.8	p=0.03	278.4	0.51
SiC adjusted for fibres and cristobalite	0.9	0.5 to 1.6	p=0.2	278.8
SiC adjusted for cristobalite	0.9	0.5 to 1.6	p=0.02	277.5	0.74
SiC adjusted for cristobalite and fibres	0.9	0.5 to 1.6	p=0.4	278.8

^*LR-test: Likelihood ratio test comparing the actual model with the model containing one less exposure factor.

^†r_Pearson: Pearson's correlation coefficient.

PYR, person - years; AIC, Akaike's Information Criterion; SiC, silicon carbide.