All workers | Cases N (%) | Controls |
---|---|---|
Total | 80 | 315 |
Female | 0 (0.0) | 17 (5.4) |
Male | 80 (100.0) | 298 (94.6) |
Type of ore mining | ||
Haematite only | 23 (28.7) | 131 (41.6) |
Taconite and haematite | 25 (31.3) | 81 (25.7) |
Taconite only | 32 (40.0) | 103 (32.7) |
Years of employment (years) | Mean (SD) | Mean (SD) |
Taconite employment | 7.7 (9.6) | 5.5 (8.4) |
Haematite employment (years) | 2.8 (6.2) | 3.1 (5.9) |
Total employment | 10.6 (11.6) | 8.6 (10.9) |
Taconite workers | Cases N (%) | Controls N (%) |
Total | 57 | 184 |
Female | 0 (0.0) | 9 (4.9) |
Male | 57 (100.0) | 175 (95.1) |
Geological zone-ever worked* | ||
Zone 1 | 18 (31.6) | 74 (40.2) |
Zone 2 | 31 (54.4) | 58 (31.5) |
Zone 4 | 12 (21.1) | 66 (35.9) |
Years of employment | Mean (SD) | Mean (SD) |
Total employment | 13.7 (11.8) | 13.3 (12.0) |
Taconite employment | 10.9 (9.7) | 9.4 (9.3) |
Hematite employment | 2.9 (6.3) | 4.0 (7.0) |
Employment by geological zone (years) | ||
Zone 1 | 3.5 (6.7) | 3.1 (5.6) |
Zone 2 | 5.7 (9.1) | 2.5 (6.8) |
Zone 4 | 1.6 (5.9) | 3.7. (8.1) |
NIOSH 7400 (EMP/cc)×years | Mean (SD) | Mean (SD) |
Total (EMP/cc)×years | 2.2 (1.2) | 1.7 (0.4) |
(EMP/cc)×years by geological zone | ||
Zone 1 | 0.5 (1.2) | 0.1 (0.4) |
Zone 2 | 1.4 (2.1) | 0.5 (1.5) |
Zone 4 | 0.4 (1.4) | 1.0 (2.3) |
Employment in SEGs with high commercial asbestos† (years) | 1.6 (3.8) | 0.8 (2.8) |
*Cases and controls may have worked in multiple zones.
†SEGs with a high asbestos score are crusher maintenance, furnace operator, electrician, carpenter, auto mechanic, pipefitter/plumber, and lubricate technician.
EMP, elongate mineral particles; NIOSH, National Institute for Occupational Safety and Health; SEGs, similar exposure groups.