Table 3.

Observed number of cases (Obs) and standardised incidence ratio (SIR), with 95% CIs of lung cancer among 1687 long-term Norwegian silicon carbide (SiC) industry workers employed during 1913–2003 and followed up during 1953–2008, by tertiles of cumulative exposure, and with exposure lagging 0 and 20 years

	No lag					20 years lag of exposure
Cumulative exposure	N	Person-years	Obs	SIR	95% CI	N	Person-years	Obs	SIR	95% CI
Total dust (mg × years/m3)
0–30	1101	14 349	9	0.9	0.5 to 1.7	1615	32 343	23	1.1	0.8 to 1.7
30–87	1001	14 188	15	1.4	0.9 to 2.4	675	5700	13	1.5	0.9 to 2.6
87–900	671	14 374	38	2.2	1.6 to 3.1	351	4867	26	3.0	2.0 to 4.4
Respirable dust (mg × years/m3)
0–3.8	1156	14 186	9	0.9	0.4 to 1.7	1623	33 047	25	1.2	0.8 to 1.8
3.8–10	1066	14 082	20	1.8	1.2 to 2.8	651	5495	16	1.9	1.2 to 3.1
10–87	701	14 642	33	2.0	1.4 to 2.9	342	4367	21	2.6	1.7 to 3.9
Quartz (mg × years/m3)
0–0.026	1096	14 286	11	1.1	0.6 to 1.9	1619	32 564	29	1.4	1.0 to 2.0
0.026–0.077	998	14 169	20	1.8	1.1 to 2.7	653	5447	15	1.8	1.1 to 3.0
0.077–2.3	668	14 455	31	1.9	1.4 to 2.7	344	4899	18	2.0	1.3 to 3.3
Cristobalite (mg × years/m3)
0–0.028	1030	14 083	10	1.0	0.5 to 1.8	1616	32 592	25	1.2	0.8 to 1.8
0.028–0.093	902	14 346	17	1.4	0.9 to 2.3	645	5344	17	2.0	1.2 to 3.2
0.093–2.7	673	14 480	35	2.3	1.6 to 3.2	351	4974	20	2.4	1.5 to 3.7
SiC (mg × years/m3)
0–0.83	970	14 111	14	1.3	0.7 to 2.1	1616	32 293	27	1.3	0.9 to 1.9
0.83–3.0	941	14 096	14	1.3	0.8 to 2.2	677	5865	14	1.6	0.9 to 2.7
3.0–60	697	14 703	34	2.2	1.6 to 3.1	357	4752	21	2.6	1.7 to 3.9
Fibres (fibres × years/cm3)
0–0.50	925	13 788	13	1.2	0.7 to 2.1	1619	31 648	24	1.2	0.8 to 1.8
0.50–2.0	1018	14 897	15	1.3	0.8 to 2.2	682	6466	14	1.6	0.9 to 2.6
2.0–93	614	14 225	34	2.2	1.6 to 3.0	336	4796	24	2.6	1.8 to 3.9