Table 5.
Adjusted odds ratios (OR) and corresponding 95 % confidence intervals (CI) for rectal cancer and colon cancer in relation to occupational exposure to gasoline emissions
| Rectal cancer (n = 840) | Colon cancer (n = 931) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Exposure metrica | Cases (%) | Controls (%) | ORb | (95 % CI) | Cases (%) | Controls (%) | ORb | (95 % CI) | ||||||
| Ever exposed | ||||||||||||||
| No | 452 | (53.8) | 783 | (57.6) | 1.00 | 505 | (54.2) | 783 | (57.6) | 1.00 | ||||
| Yes | 388 | (46.2) | 577 | (42.4) | 1.12 | (0.91, | 1.38) | 426 | (45.8) | 577 | (42.4) | 1.04 | (0.85, | 1.27) |
| Highest attained exposure concentration | ||||||||||||||
| Unexposed | 452 | (53.8) | 783 | (57.6) | 1.00 | 505 | (54.2) | 783 | (57.6) | 1.00 | ||||
| Low | 305 | (36.3) | 462 | (34.0) | 1.20 | (0.96, | 1.50) | 342 | (36.7) | 462 | (34) | 1.10 | (0.88, | 1.37) |
| Medium | 55 | (6.6) | 71 | (5.2) | 1.12 | (0.73, | 1.73) | 54 | (5.8) | 71 | (5.2) | 0.92 | (0.60, | 1.42) |
| High | 28 | (3.3) | 44 | (3.2) | 1.04 | (0.60, | 1.79) | 30 | (3.2) | 44 | (3.2) | 1.04 | (0.61, | 1.76) |
| p-trend | 0.74 | p-trend | 0.91 | |||||||||||
| Duration of exposure (years) | ||||||||||||||
| Unexposed | 452 | (54.3) | 783 | (58.1) | 1.00 | 505 | (55.0) | 783 | (58.1) | 1.00 | ||||
| > 0 to <7 | 117 | (14.1) | 179 | (13.3) | 1.09 | (0.82, | 1.46) | 128 | (13.9) | 161 | (11.9) | 1.00 | (0.76, | 1.34) |
| ≥ 7 to ≤26 | 144 | (17.3) | 196 | (14.5) | 1.20 | (0.91, | 1.59) | 141 | (15.4) | 185 | (13.7) | 0.96 | (0.73, | 1.27) |
| > 26 | 120 | (14.4) | 190 | (14.1) | 1.08 | (0.77, | 1.51) | 144 | (15.7) | 219 | (16.3) | 1.10 | (0.79, | 1.51) |
| p-trend | 0.33 | p-trend | 0.77 | |||||||||||
| Duration of exposure at high concentration (years) | ||||||||||||||
| Unexposed | 812 | (96.8) | 1316 | (97.1) | 1.00 | 901 | (97.0) | 1316 | (97.1) | 1.00 | ||||
| > 0 to <5 | 15 | (1.8) | 21 | (1.6) | 1.02 | (0.48, | 2.16) | 15 | (1.6) | 21 | (1.6) | 0.94 | (0.46, | 1.94) |
| ≥ 5 | 12 | (1.4) | 18 | (1.3) | 1.08 | (0.48, | 2.39) | 13 | (1.4) | 18 | (1.3) | 1.13 | (0.51, | 2.52) |
| p-trend | 0.84 | p-trend | 0.84 | |||||||||||
| Frequency of exposure | ||||||||||||||
| Unexposed | 528 | (64.6) | 852 | (66.6) | 1.00 | 582 | (63.8) | 852 | (66.6) | 1.00 | ||||
| Low: 5 % | 14 | (1.7) | 56 | (4.4) | 0.46 | (0.24, | 0.89) | 32 | (3.5) | 56 | (4.4) | 0.85 | (0.51, | 1.42) |
| Medium: 6–30 % | 213 | (26.0) | 282 | (22.0) | 1.08 | (0.84, | 1.40) | 224 | (24.5) | 282 | (22.0) | 1.08 | (0.84, | 1.38) |
| High: >30 % | 63 | (7.7) | 90 | (7.0) | 1.00 | (0.68, | 1.48) | 75 | (8.2) | 90 | (7.0) | 1.16 | (0.80, | 1.66) |
| p-trend | 0.72 | p-trend | 0.30 | |||||||||||
| Cumulative occupational exposurec | ||||||||||||||
| Unexposed | 452 | (54.3) | 783 | (58.0) | 1.00 | 505 | (55.0) | 783 | (58.0) | 1.00 | ||||
| Lowest tertile | 117 | (14.1) | 175 | (13.0) | 1.13 | (0.84, | 1.51) | 108 | (11.8) | 144 | (10.7) | 0.85 | (0.63, | 1.15) |
| Middle tertile | 140 | (16.8) | 204 | (15.1) | 1.14 | (0.86, | 1.51) | 168 | (18.3) | 217 | (16.1) | 1.13 | (0.87, | 1.48) |
| Highest tertile | 124 | (14.9) | 187 | (13.9) | 1.11 | (0.81, | 1.51) | 138 | (15.0) | 205 | (15.2) | 1.06 | (0.78, | 1.43) |
| p-trend | 0.38 | p-trend | 0.55 | |||||||||||
aExposures were restricted to estimates with reliability > possible; estimates with low reliability were classified as unexposed
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)
cCumulative metric of exposure to diesel emissions was derived from estimates of concentration of exposure, frequency of exposure and duration of employment