Table 1.
Characteristics of cases and controls
| CASES (N=1706) | CONTROLS (N=3381) | |
|---|---|---|
|
| ||
| N (%) | N (%) | |
| Sex | ||
| Male | 1637 (95.96) | 3183 (94.14) |
| Female | 69 (4.04) | 198 (5.86) |
|
| ||
| Ore type | ||
| Taconite only | 668 (39.16) | 1239 (36.67) |
| Hematite only | 738 (43.26) | 1532 (45.28) |
| Taconite & hematite | 300 (17.58) | 610 (18.05) |
|
| ||
| Ever worked by zone | ||
| Zone 1 | 347 (20.34) | 642 (18.99) |
| Zone 2 | 366 (21.45) | 618 (18.28) |
| Zone 4 | 327 (19.17) | 699 (20.67) |
|
| ||
| Mean (SD)a | Mean (SD) | |
|
| ||
| Birthyear | 1930 (7.92) | 1930 (7.90) |
|
| ||
| Years of employment | ||
| Taconite | 7.67 (8.22) | 8.52 (8.57) |
| Hematite | 3.57 (5.34) | 3.67 (5.58) |
|
| ||
| Years of taconite employment by zone | ||
| Zone 1 | 7.38 (5.97) | 7.60 (5.76) |
| Zone 2 | 5.41 (7.88) | 7.11 (8.48) |
| Zone 4 | 8.81 (9.74) | 9.27 (10.26) |
|
| ||
| (EMP/cc)*years | ||
| Totalb | 1.48 (2.17) | 1.68 (2.31) |
| Zone 1 | 0.52 (1.00) | 0.52 (0.94) |
| Zone 2 | 1.17 (1.75) | 1.54 (1.94) |
| Zone 4 | 2.51 (2.74) | 2.61 (2.85) |
|
| ||
| Silica (mg/m3)*years | ||
| Totalb | 0.28 (0.31) | 0.31 (0.31) |
|
| ||
| Years of employment by department | ||
| Mining | 1.28 (3.50) | 1.36 (3.79) |
| Crushing | 0.16 (0.92) | 0.20 (1.00) |
| Concentrating | 0.20 (1.18) | 0.22 (1.23) |
| Pelletizing | 0.25 (1.64) | 0.24 (1.56) |
| Shop mobile | 2.59 (5.50) | 2.98 (5.79) |
| Shop stationary | 0.68 (2.76) | 0.71 (2.59) |
| Office | 0.30 (1.93) | 0.65 (2.97) |
| Missing/unknown | 0.48 (2.17) | 0.46 (2.36) |
| General mine | 0.69 (2.56) | 0.47 (2.02) |
| General plant | 0.38 (1.85) | 0.44 (2.22) |
| General shop | 0.68 (2.53) | 0.79 (2.73) |
a
SD = standard deviation
b
mean cumulative exposure