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Hard metal disease (HMD), the interstitial lung disease caused by dusts in the cemented tungsten carbide (WC) industry, has been attributed to cobalt. The rare histologic pattern of giant cell interstitial pneumonia (GIP) is characteristic in HMD. The authors reviewed the history of HMD and 100 cases of HMD that they have seen over 5 decades. GIP was proven in 59; analysis of the lung inorganic particle burden by scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed HMD in the other 41. Cases have been diagnosed by bronchoalveolar lavage, lung biopsy, and autopsy. Histopathology findings range from focal peribronchiolar inflammation to diffuse interstitial fibrosis and honeycombing. GIP cases in the WC industry reveal elevated concentrations of tungsten in all, but cobalt was detected in only 6 ( approximately 10%). Of the 746 diverse cases in the authors' analytical database, almost all cases with the highest tungsten concentration showed GIP. This study confirms that GIP is effectively pathognomonic for HMD.

The authors report the case of a 65-year-old accountant whose only asbestos exposure was during a summer job 50 years earlier in a California vermiculite expansion plant. Vermiculite is a silicate material that is useful in building and agriculture as a filler and insulating agent. He developed extensive fibrocalcific pleural plaques and end-stage pulmonary fibrosis, with rapidly progressive respiratory failure. Careful occupational and environmental history revealed no other source of asbestos exposure, and the initial clinical diagnosis was idiopathic pulmonary fibrosis; open lung biopsy shortly before his death confirmed asbestosis. Electron microscopic lung fiber burden analysis revealed over 8,000,000 asbestos fibers per gram dry lung, 68% of which were tremolite asbestos. Additional asbestiform fibers of composition not matching any of the standard asbestos varieties were also present at over 5,000,000 fibers per gram dry lung. Comparison analysis of a sample of Libby, Montana, vermiculite showed a similar mix of asbestiform fibers including tremolite asbestos. This case analysis raises several concerns: risks of vermiculite induced disease among former workers of the more than 200 expansion plants throughout the United States; health effects of brief but very high-intensity exposures to asbestos; and possible health effects in end-users of consumer products containing vermiculite.