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Table 3 Workplace silica exposure and bladder cancer in men from the NECSS, 1994–1997

From: Silica and asbestos exposure at work and the risk of bladder cancer in Canadian men: a population-based case-control study

Silica exposure groupsCasesControlsMinimal aFull b
N%N%OR (95% CI)OR (95% CI)
Ever exposed to silica
 Never40420.092946.01.001.00
 Ever25412.643121.41.27 (1.00–1.61)1.20 (0.95–1.51)
  ≥ 20 years ago57 88 1.29 (0.89–1.88)1.14 (0.79–1.66)
  ≥ 40 years ago146 254 1.21 (0.94–1.55)1.06 (0.82–1.38)
Highest attained concentration of exposure to silica
 Unexposed40420.092946.01.001.00
 Low21810.836918.31.23 (0.99–1.53)1.24 (0.98–1.58)
 Medium/ High361.8623.11.14 (0.73–1.79)0.96 (0.60–1.54)
 p-trend    0.050.13
Highest attained frequency of exposure to silica
 Unexposed40420.092946.01.001.00
  < 5%180.9512.50.82 (0.46–1.46)0.81 (0.45–1.46)
 5–30%1607.927413.61.21 (0.95–1.55)1.26 (0.97–1.64)
  ≥ 30%763.81065.31.38 (0.99–1.93)1.22 (0.84–1.77)
 p-trend    0.030.09
Duration of exposure to silica (years)
 Unexposed40420.092946.01.001.00
  <  7783.91346.61.20 (0.87–1.64)1.17 (0.84–1.63)
 7- < 27673.31185.91.12 (0.80–1.57)1.02 (0.73–1.43)
  ≥ 27994.91648.11.29 (0.96–1.74)1.41 (1.01–1.98)
 Unknown100.5150.7  
 p-trend    0.070.16
Duration of exposure at low concentrations of silica (years)  
Unexposed42120.996848.01.001.00
< 7753.71246.11.21 (0.88–1.68)1.20 (0.86–1.68)
7 - < 27693.41236.11.14 (0.82–1.59)1.09 (0.77–1.55)
≥ 27834.11326.51.38 (1.00–1.91)1.52 (1.07–2.14)
Unknown100.5130.6  
p-trend    0.030.07
Duration of exposure at medium/high concentrations of silica (years)
 Unexposed62230.8129864.31.001.00
  < 7180.9301.51.20 (0.65–2.22)1.07 (0.57–2.00)
  ≥ 7180.9301.51.00 (0.54–1.88)0.76 (0.39–1.46)
 Unknown00.020.1  
 p-trend    0.850.67
Cumulative exposure to silica
 Unexposed40420.092946.01.001.00
 Lowest tertile854.21326.51.26 (0.92–1.72)1.24 (0.90–1.71)
 Middle tertile663.31406.91.02 (0.73–1.42)1.03 (0.73–1.46)
 Highest tertile934.61447.11.35 (0.99–1.83)1.29 (0.92–1.81)
 Unknown100.5150.7  
 p-trend    0.080.18
  1. a Adjusted for province of residence, age at interview, respondent status, cigarette pack-years
  2. b Adjusted for province of residence, age at interview, proxy respondent, cigarette pack-years, highest attained concentration of diesel exposure, ever exposed to mineral/lube oil at work