New developments in occupational asthma.

Recent developments in occupational asthma are reviewed. There are now three independent estimates of the incidence of occupational asthma in the general working population, which all identify the same high risk occupational groups (particularly those exposed to isocyanates and flour or wheat). The incidence of occupational asthma principally depends on the agent and level of exposure. The property of a small molecular weight chemical to bind to and alter the structure of body proteins seems important. Smoking both increases the number of workers developing specific IgE to occupational agents, and the number developing occupational asthma. The relation between increased non-specific bronchial responsiveness and occupational asthma is reviewed. Occupational sensitisation may be the cause of hyperresponsiveness, or develop in those with pre-existing hyperresponsiveness. Around 20% of workers with occupational asthma have measurements within the normal range. Once occupational asthma develops, removal from exposure, particularly if delayed, often results in continuing asthma. Finally the prevention of occupational asthma is discussed.