Comparison of the possible confounding factors among the different exposure categories
| Control | Exposed | |||||||
|---|---|---|---|---|---|---|---|---|
| Total | Current work type* | Cumulative exposure length, years† | ||||||
| Production | Development | Maintenance | 1–10 | 11–20 | 21+ | |||
| *Production: toner production; development: machine development; maintenance: machine maintenance. | ||||||||
| †Excluding seven subjects with unverified exposure length. | ||||||||
| ‡One machine development worker with a duration of exposure of 1–10 years was excluded because of unspecified smoking history. | ||||||||
| §Significant difference from the mean value in the control group by analysis of variance. | ||||||||
| The figures show the means (standard deviation) for age, height, and body mass index (BMI), and the number of subjects (% of the column total) with a current smoking habit. | ||||||||
| Surveyed, n | 212 | 600 | 142 | 114 | 344 | 271 | 295 | 27 |
| Age (years) | 38 (9) | 35§ (8) | 39 (11) | 36§ (6) | 32§ (5) | 33§ (9) | 35§ (5) | 44§ (5) |
| Height (cm) | 170 (6) | 171 (6) | 170 (6) | 171 (5) | 172§ (6) | 171 (6) | 171 (6) | 170 (6) |
| BMI (kg/m2) | 23 (3) | 23 (3) | 23 (3) | 23 (3) | 23 (3) | 23 (3) | 23 (3) | 23 (4) |
| Smoking habit‡ | ||||||||
| Never | 58 (27) | 157 (26) | 32 (23) | 45 (40) | 80 (23) | 84 (31) | 64 (22) | 7 (26) |
| Former | 27 (13) | 71 (12) | 17 (12) | 21 (19) | 33 (10) | 31 (12) | 36 (13) | 3 (11) |
| Current | 127 (60) | 371 (62) | 93 (65) | 47 (41) | 231 (67) | 155 (57) | 195 (66) | 17 (63) |