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Table 2 Adjusted odds ratios (OR) and corresponding 95 % confidence intervals (CI) for colorectal cancer in relation to occupational exposure to diesel emissions

From: Workplace exposure to diesel and gasoline engine exhausts and the risk of colorectal cancer in Canadian men

Exposure Metrica

Cases (%)

Controls (%)

ORb (95 % CI)

Ever exposed

 No

1133

(64.0)

869

(63.9)

1.00

  

 Yes

638

(36.0)

491

(36.1)

0.88

(0.74,

1.06)

Highest attained exposure concentration

 Unexposed

1133

(64.0)

869

(63.9)

1.00

  

 Low

450

(25.4)

377

(27.7)

0.79

(0.65,

0.96)

 Medium

136

(7.7)

89

(6.5)

1.00

(0.73,

1.36)

 High

52

(2.9)

25

(1.8)

1.65

(0.98,

2.80)

 p-trend

    

0.78

  

Duration of exposure (years)

 Unexposed

1133

(64.5)

869

(64.4)

1.00

  

  > 0 to <11

208

(11.9)

157

(11.6)

0.90

(0.70,

1.16)

  ≥ 11 to ≤31

220

(12.5)

166

(12.3)

0.91

(0.71,

1.18)

  > 31

195

(11.1)

157

(11.6)

0.80

(0.60,

1.08)

 p-trend

    

0.11

  

Duration of exposure at high concentration (years)

 Unexposed

1719

(97.2)

1335

(98.2)

1.00

  

  > 0 to ≤10

29

(1.6)

13

(1.0)

1.60

(0.80,

3.21)

  > 10

21

(1.2)

11

(0.8)

1.90

(0.85,

4.23)

 p-trend

    

0.04

  

Frequency of exposure

 Unexposed

1191

(68.8)

910

(71.1)

1.00

  

 Low: 5 %

76

(4.4)

60

(4.7)

1.21

(0.80,

1.82)

 Medium: 6–30 %

351

(20.3)

229

(17.9)

1.10

(0.88,

1.38)

 High: >30 %

113

(6.5)

81

(6.3)

1.06

(0.76,

1.48)

 p-trend

    

0.37

  

Cumulative occupational exposurec

 Unexposed

1133

(64.5)

869

(64.6)

1.00

  

 Lowest tertile

174

(9.9)

139

(10.3)

0.86

(0.65,

1.14)

 Middle tertile

246

(14.0)

183

(13.6)

0.85

(0.66,

1.09)

 Highest tertile

158

(11.6)

158

(11.7)

0.89

(0.69,

1.15)

 p-trend

    

0.24

  

Total

1771

(100.0)

1360

(100.0)

   
  1. aExposures were restricted to estimates with reliability > possible; estimates with low reliability were classified as unexposed
  2. bAdjusted for age, province of residence, use of proxy respondents, BMI categories, percent change in weight from maximum lifetime weight, cigarette pack years, combined physical activity index (hours/month), alcohol consumption (servings/week), consumption of processed meat (servings/week), occupational exposure to asbestos (yes/no), occupational exposure to aromatic amines (yes/no)
  3. cCumulative metric of exposure to diesel emissions was derived from estimates of concentration of exposure, frequency of exposure and duration of employment