Table 1: Study population and final study sample for questionnaires and spirometries distributed according to occupational group.
| Demolition workers | Insulators | Carpenters | Hospital porters | Total | |
| N (%)* | N (%)* | N (%)* | N (%)* | N (%)* | |
| Study population | 169 | 209 | 357 | 516 | 1251 |
| Questionnaire responders | 151 (89.3) | 204 (97.6) | 321 (89.9) | 360 (69.8) | 1036 (82.8) |
| Questionnaires and spirometries | 141 (83.4) | 149 (71.3) | 296 (82.9) | 313 (60.7) | 899 (71.9) |
*percentage of study population for each occupational group