Preventing occupational asthma.

What are the priorities for prevention of occupational asthma? Five years ago, it seemed difficult to prevent without further information on exposure-response relations obtained by prospective epidemiological studies incorporating measurement of environmental exposure.' This need is now accepted so that not only are such studies being carried out but it is also possible to view prevention with a broader perspective. Prevention Prevention is grouped into primary, secondary, and tertiary preventive activities. For occupational asthma, primary prevention means controlling the exposures that cause asthma. Secondary prevention is the detection of asthma at a sufficiently early stage that impairment and disability are minimised. Ter-tiary prevention is the provision of medical care of good quality to patients with asthma so as to avert complications. Primary prevention Prevention of the exposures that cause asthma starts with a clear concept of the two causal pathways to asthma at work. A sensitising agent may induce asthma; a high molecular weight agent may act alone or a low molecular weight hapten may conjugate with body proteins. Several hundred sensitising agents that can cause asthma are known.2 Secondly, heavy exposure to an inhaled irritant such as acetic acid may induce asthma.3 This was termed "reactive airways dysfunction syndrome (RADS)" when it was first described in 1985 by Brooks and colleagues.4 The term "occupational asthma" has implied sensitiser induced asthma to most British chest physicians and occupational physicians for many years. American usage is different and occupational asthma without qualification may mean not only irritant induced asthma but also asthma exacerbated by work. Harber' has listed 12 asthma-occupation interactions and his article indicates some of the complications and uncertainties surrounding work, medical care, and asthma in the United States. This editorial concerns itself primarily with sensit-iser induced asthma. The control of sensitisers at work, and of allergic diseases, is a relatively new area. The label "allergy" may lead to an erroneous assumption from industry that these diseases cannot be controlled by primary prevention because they are due to personal idiosyncrasy. The casuistically inclined could argue the same for lung cancer or pulmonary fibrosis. To quote a recent text on preventing occupational disease and injury, "the central public health questions are what occupational exposures need to be controlled, when, and how. [Control involves] anticipation. .. surveillance, analysis, and control."' The first step in prevention is, therefore, identifying what exposures to control. Because there are many sensitising agents, there are some …