Hard Metal Pneumoconiosis


  • First reported in Germany in the 1940 s
  • Hard metal disease occurs in 5% of cobalt-exposed workers (<3% of exposed workers develop fibrosis)
  • Genetics: association with HLA-DP alleles
  • Lung Cancer Risk: increased in patients exposed to both cobalt and tungsten carbide


1) Cobalt Exposure:
a) Diamond Polishing/Tooling:
b) Sharpening of Hard Metal Tools:
c) Hard Metal Production:
d) Oil-Well Drilling: using cemented tungsten carbide
e) Armored Plate Production: tanks, naval ships
f) Manufacture of Cutting Tools/Loops for Fishing Poles:


  • ILD: probably a hypersensitivity pneumonitis to cobalt -> cobalt reacts with metallic carbides to produce reactive oxygen species
  • Cobalt exposure can also cause occupational asthma, bronchitis, BOOP, and an acute chemical pneumonitis (with high level exposure)

Pathologic Patterns

  • ILD: thickening of alveolar septa with multinucleated giant cells


  • FOB: see below
  • PFT’s: see below
  • CXR/Chest CT Patterns:
    • ILD:
  • Cobalt Skin Patch Test: detects cobalt exposure
  • Urine/Blood/Hair Samples: detects cobalt
  • Lymphocyte Transformation Test to Cobalt (Using BAL or Blood Lymphocytes): may be useful


Clinical Presentations: features from each of these presentations may co-exist in the same patient
1) Acute Hard Metal Disease: more common manifestation than ILD presentation
a) Rhinitis/Conjunctivitis: due to fact that cobalt is a skin sensitizer
b) Occupational Asthma:
c) Bronchitis:
d) Skin Symptoms: due to fact that cobalt is a skin sensitizer

2) Subacute Hard Metal Disease:
a) Fibrosing Alveolitis:

3) Chronic Hard Metal Disease: rare manifestation
a) Diffuse and Progressive Interstitial Fibrosis: dyspnea, hypoxemia
-FOB with BAL: multinucleated cannabilistic -appearing cells in BAL fluid ( cell within a cell apprearance)
–Multinucleated giant cells stain positive for cytokeratin (may represent epithelial cells)
–Multinucleated giant cells comprise up to 15% of total BAL cells
-OLB: giant cell interstitital pneumonia (GIP) is almost pathognomonic for Hard Metal Pneumoconiosis
–Tungsten carbide can be identified on biopsy (but due to solubility, cobalt is usually not detected)


  • Total Cessation of Cobalt Exposure: crucial to prevent disease progression to chronic ILD
  • Steroids: have been used
  • Cytoxan: have been used