Number of respirable crystalline silica samples collected, adjusted and unadjusted geometric means (GM) and standard deviations (GSD), maximum level, and percentage exceeding the maximum exposure level by job, quarry, and year group
| Number of samples (%) | Adjusted GM (mg/m3) (GSD) | Unadjusted GM (mg/m3) (GSD) | Maximum (mg/m3) | % >MEL | |
|---|---|---|---|---|---|
| GM, geometric mean; GSD, geometric standard deviation; MEL, maximum exposure limit 0.30 mg/m3. | |||||
| Brickworks/wet, brickworks/dry, brickworks/drivers, and office workers assumed to have similar exposures to wet process, dry/dryers, dry/others, and site management. | |||||
| Job category | |||||
| Sand winner | 207 (6.9) | 0.09 (3.8) | 0.06 (5.0) | 1.17 | 10.6 |
| Wet process | 141 (4.7) | 0.05 (3.6) | 0.04 (4.2) | 0.73 | 3.5 |
| Dry, dryer | 572 (19.0) | 0.08 (4.0) | 0.09 (3.6) | 4.10 | 15.0 |
| Dry, bagger | 461 (15.3) | 0.11 (4.0) | 0.10 (3.4) | 13.97 | 16.5 |
| Dry, other | 513 (17.0) | 0.11 (4.4) | 0.11 (4.0) | 9.05 | 12.5 |
| Laboratory technician | 234 (7.8) | 0.07 (3.6) | 0.06 (3.6) | 0.96 | 6.0 |
| Driver, HGV | 11 (0.4) | 0.04 (3.4) | 0.08 (2.4) | 0.24 | |
| Driver, other | 19 (0.6) | 0.04 (3.4) | 0.04 (6.4) | 1.68 | 5.3 |
| Site maintenance | 55 (1.8) | 0.05 (3.5) | 0.04 (4.3) | 1.65 | 7.3 |
| Workshop | 4 (0.1) | 0.03 (3.3) | 0.02 (3.7) | 0.16 | |
| Site management | 30 (1.0) | 0.03 (3.4) | 0.02 (3.2) | 0.30 | 3.3 |
| Silica flour | 765 (25.4) | 0.10 (5.9) | 0.13 (3.1) | 12.01 | 16.6 |
| Quarry (group) | |||||
| 1 (A) | 159 (5.3) | 0.05 (4.1) | 0.05 (4.7) | 1.87 | 3.1 |
| 2 (B) | 70 (2.3) | 0.05 (3.8) | 0.03 (4.1) | 1.17 | 5.7 |
| 3 (B) | 347 (11.5) | 0.05 (6.2) | 0.06 (4.3) | 13.97 | 8.1 |
| 4 (C) | 415 (13.8) | 0.06 (7.0) | 0.08 (4.5) | 9.05 | 11.1 |
| 5 (D) | 308 (10.2) | 0.07 (5.7) | 0.07 (3.7) | 2.98 | 9.1 |
| 6 (D) | 1045 (34.7) | 0.06 (14.4) | 0.10 (3.2) | 8.84 | 13.2 |
| 7 (E) | 668 (22.2) | 0.10 (9.0) | 0.14 (3.7) | 12.01 | 22.6 |
| Year group | |||||
| 1978–1985 | 1240 (41.2) | 0.08 (17.9) | 0.13 (3.2) | 7.29 | 19.4 |
| 1986–1994 | 1388 (46.1) | 0.05 (19.0) | 0.08 (4.3) | 12.01 | 8.8 |
| 1995–2000 | 384 (12.7) | 0.04 (6.0) | 0.06 (4.0) | 13.97 | 9.9 |
| Total | 3012 (100.0) | 0.09 (3.9) | 13.97 | 13.3 | |