Metals

While the numerical contribution of metal-induced asthma to the overall prevalence of occupational asthma (OA) appears to be relatively small, OA due to some metals, platinum salts in particular, poses an important health problem in precious metals refineries and catalyst production. The spectrum of pulmonary toxicity due to inhalation of metallic compounds encompasses a wide range of acute and chronic obstructive syndromes, which in some instances may mimic asthma. Asthma induced by metals may be immunologically mediated OA or due to irritation. A few metals like platinum and metals that belong to the transition metals of the fourth, fifth, and sixth periods of the elements may cause OA via an immunologic mechanism. Sensitization generally occurs by inhalation but can occur by skin exposure. Many studies have investigated immunological sensitization and OA in workers exposed to platinum. Traditionally, the primary route of exposure for the induction of sensitization to metals was considered via inhalation but absorption can also occur through the skin. It has been shown that reducing exposure to platinum and medical surveillance of exposed workers can offer a satisfactory protection. Other metals that can cause OA are chromium, nickel, cobalt, zinc, and manganese. An immunological mechanism cannot be elicited for some types of OA, like for “potroom asthma” that occurs in aluminum production. Welders can also be affected by metal fume fever and OA but the mechanism remains unknown.