Table 1

Characteristics of all cases and controls in study population, and cases and controls who worked in taconite

All workersCases N (%)Controls
Total80315
Female0 (0.0)17 (5.4)
Male80 (100.0)298 (94.6)
Type of ore mining
 Haematite only23 (28.7)131 (41.6)
 Taconite and haematite25 (31.3)81 (25.7)
 Taconite only32 (40.0)103 (32.7)
Years of employment (years)Mean (SD)Mean (SD)
Taconite employment7.7 (9.6)5.5 (8.4)
Haematite employment (years)2.8 (6.2)3.1 (5.9)
Total employment10.6 (11.6)8.6 (10.9)
Taconite workersCases N (%)Controls N (%)
Total57184
Female0 (0.0)9 (4.9)
Male57 (100.0)175 (95.1)
Geological zone-ever worked* 
 Zone 118 (31.6)74 (40.2)
 Zone 231 (54.4)58 (31.5)
 Zone 412 (21.1)66 (35.9)
Years of employmentMean (SD)Mean (SD)
Total employment13.7 (11.8)13.3 (12.0)
Taconite employment10.9 (9.7)9.4 (9.3)
Hematite employment2.9 (6.3)4.0 (7.0)
Employment by geological zone (years) 
 Zone 13.5 (6.7)3.1 (5.6)
 Zone 25.7 (9.1)2.5 (6.8)
 Zone 41.6 (5.9)3.7. (8.1)
NIOSH 7400 (EMP/cc)×yearsMean (SD)Mean (SD)
Total (EMP/cc)×years2.2 (1.2)1.7 (0.4)
(EMP/cc)×years by geological zone
 Zone 10.5 (1.2)0.1 (0.4)
 Zone 21.4 (2.1)0.5 (1.5)
 Zone 40.4 (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.