ABSTRACT
Various chemical substances can cause occupational asthma. Chemicals most often implicated as a cause of occupational asthma are the polyisocyanates (Chapter 21). Although the majority of subjects, consulting for possible occupational asthma (OA), are exposed to low-molecular-weight agents (more so than in the case of highmolecular-weight agents), most of the other agents have also been documented in individual case reports. The frequency of occupational asthma caused by these agents has generally not been determined either because the agents are not used extensively or because no sufficient interest was found in carrying out the studies. The mechanism of sensitization has only been determined for some of the agents. Some substances have been found to mediate sensitization through an immunoglobulin (Ig) E-dependent mechanism. Low-molecular-weight agents, which represent the majority of these miscellaneous chemical substances, may cause sensitization by acting as haptens. However, the mechanism of asthma induction remains inconclusive for many other low-molecular-weight agents.
