Table 3

Standardised mortality ratios (SMR) and Poisson regression analyses (incidence rate ratios, IRR) with 95% CIs of obstructive lung diseases as underlying (OLD-u) or underlying or contributing (OLD-uc) cause of death 1951–2007, by cumulative exposure groups, among Norwegian long-term silicon carbide industry workers employed 1913–1920

All employees (N=1687)All ever-smokers (N=1162)<15 years employment, ever-smokers (N=1115)≥15 years employment, ever-smokers (N=599)
OLD-u (45 cases)OLD-u (38 cases)OLD-uc (55 cases)OLD-uc (32 cases)OLD-uc (23 cases)
SMR95% CIIRR*95% CIPtrendIRR*95% CIPtrendIRR*95% CIPtrendIRR*95% CIPtrend
Total dust
 Low0–28.6 mg×years/m31.40.7 to 2.81.01.01.01.0
 Medium28.7–86.1 mg×years/m32.61.6 to 4.22.80.9 to 8.51.70.7 to 4.11.30.5 to 3.42.20.2 to 24.5
 High≥86.2 mg×years/m31.91.2 to 2.92.50.8 to 7.4p=0.22.41.0 to 5.5p=0.032.30.8 to 6.4p=0.15.40.7 to 40.1p=0.05
Respirable dust
 Low0–3.7 mg×years/m31.50.8 to 2.81.01.01.01.0
 Medium3.8–9.9 mg×years/m32.71.7 to 4.32.00.8 to 5.11.20.6 to 2.71.00.4 to 2.51.20.2 to 8.7
 High≥10 mg×years/m31.81.1 to 2.91.50.6 to 3.9p=0.51.60.8 to 3.3p=0.21.70.7 to 4.6p=0.32.40.6 to 10.2p=0.2
Fibre
 Low0–0.5 fibres×years/cm31.91.1 to 3.41.01.01.01.0
 Medium0.6–2.0 fibres×years/cm31.91.1 to 3.30.90.4 to 2.30.70.3 to 1.50.60.2 to 1.31.80.3 to 9.8
 High≥2.1 fibres×years/cm32.11.3 to 3.21.40.6 to 3.1p=0.41.20.6 to 2.2p=0.51.20.5 to 2.8p=0.82.60.6 to 11.4p=0.2
Silicon carbide dust
 Low0–0.7 mg×years/m30.90.4 to 2.01.01.01.01.0
 Medium0.8–2.6 mg×years/m32.81.7 to 4.43.11.0 to 9.31.90.8 to 4.41.70.6 to 4.42.40.5 to 12.1
 High≥2.7 mg×years/m32.21.4 to 3.43.41.2 to 10.2p=0.032.51.1 to 5.5p=0.022.91.1 to 7.6p=0.032.90.7 to 12.8p=0.2
Quartz
 Low0–13.7 μg×years/m32.01.2 to 3.51.01.01.01.0
 Medium13.8–50.3 μg×years/m31.70.9 to 3.10.70.3 to 1.80.90.4 to 2.00.80.3 to 1.91.90.2 to 17.0
 High≥50.4 μg×years/m32.11.4 to 3.31.30.6 to 2.8p=0.41.50.8 to 3.0p=0.21.40.6 to 3.2p=0.44.30.6 to 32.0p=0.06
Cristobalite
 Low0–10.3 μg×years/m31.70.9 to 3.01.01.01.01.0
 Medium10.4–47.6 μg×years/m31.81.0 to 3.00.70.3 to 1.90.60.3 to 1.40.70.3 to 1.70.90.2 to 4.8
 High≥47.7 μg×years/m32.41.6 to 3.71.60.7 to 3.4p=0.21.70.9 to 3.2p=0.051.40.6 to 3.1p=0.43.20.7 to 14.0p=0.02
  • * Adjusted for age (</≥75 years) and period of diagnosis (</≥1 January 1990).