Distribution of subjects according to different dimensions of diesel engine emissions exposure
| Study I | Study II | |||
| Controls, N (%) | Cases, N (%) | Controls, N (%) | Cases, N (%) | |
| Exposure dimension | ||||
| Never exposed | 455 (85.4) | 675 (78.8) | 496 (55.5) | 353 (48.0) |
| Ever exposed | 67 (12.6) | 165 (19.3) | 312 (34.9) | 298 (40.5) |
| Uncertain* exposure | 11 (2.1) | 17 (2.0) | 86 (9.6) | 85 (11.5) |
| Duration (years) | ||||
| 1–10 | 21 (3.9) | 65 (7.6) | 118 (13.2) | 127 (17.3) |
| 11–20 | 15 (2.8) | 45 (5.3) | 70 (7.8) | 52 (7.1) |
| >20 | 31 (5.8) | 55 (6.4) | 124 (13.9) | 119 (16.2) |
| Concentration | ||||
| Low | 18 (3.4) | 54 (6.3) | 218 (24.4) | 180 (24.5) |
| Medium | 43 (8.1) | 85 (9.9) | 84 (9.4) | 104 (14.1) |
| High | 6 (1.1) | 26 (3.0) | 10 (1.1) | 14 (1.9) |
| Average time/week (h) | ||||
| <2 | 12 (2.3) | 22 (2.6) | 18 (2.0) | 18 (2.4) |
| 2–12 | 33 (6.2) | 81 (9.5) | 133 (14.9) | 104 (14.1) |
| >12 | 22 (4.1) | 62 (7.2) | 161 (18.0) | 176 (23.9) |
| Cumulative exposure | ||||
| Non-substantial | 44 (8.3) | 97 (11.3) | 260 (29.1) | 224 (30.4) |
| Substantial level | 23 (4.3) | 68 (7.9) | 52 (5.8) | 74 (10.1) |
↵* Subjects with ‘possible’ exposure, but not probable or certain.