Hard metal interstitial pulmonary disease associated with a form of welding in a metal parts coating plant
We describe two cases of hard metal pulmonary disease (one fatal) in workers employed in the same area of a metal coating plant using the detonation gun process for applying a durable metal surface to metal parts. In this form of welding, a mixture of powdered metals, including tungsten carbide and cobalt, is heated by ignition of a flammable gas and propelled from the end of the "gun" at high temperature and velocity to form a welded metal coating. This process is done in an enclosed chamber and with each application, large volumes of fine aerosols are created. Inhalation exposure to hard metal may occur during the mounting and removal of the metal parts between applications, in spite of engineering controls and industrial hygiene surveillance. One of the cases presented with minimal chest x-ray abnormalities and an obstructive pattern on pulmonary function testing, although subsequent open lung biopsy showed diffuse interstitial pulmonary fibrosis. The fact that two cases of hard metal pulmonary interstitial disease occurred where thorough exposure control procedures and a surveillance program for cobalt were in place may indicate the need for revisions of the current technology used when hard metal is applied in the detonation gun process.