OCCUPATIONAL ASTHMA

Abstract

Occupational asthma is a unique clinical problem that has important medical, legal, and socioeconomic ramifications. Occupational asthma should be considered in the context of the evaluation and treatment of the difficult asthmatic because it can present many diagnostic and therapeutic challenges to the clinician. This article focuses on the practical issues that assist the physician in an accurate and timely diagnosis of occupational asthma so an appropriate management plan can be established and implemented. Unfortunately, there is no simple universally accepted definition of occupational asthma. One straightforward definition is simply “the development of variable airways obstruction caused by inhalation of dusts, vapors, fumes or gases in the workplace.”2 This description suggests that documented airways obstruction does not necessarily need to be entirely reversible. Most authors stress that significant reversibility should be documented by an improvement of the forced expiratory volume in 1 second (FEV1) of at least 12% to 15% or peak-flow improvement of 20% to 25%. In addition, it should be noted that this simple definition encompasses the possibility that occupational asthma may be superimposed on underlying nonoccupational asthma that has been worsened by workplace exposures. Asthma is an increasingly common disorder with significant morbidity and mortality. Worldwide it is estimated that approximately 2% to 15% of all cases of asthma are occupational in origin.8, 14 Some 250 causative agents have been implicated in the induction of occupational asthma.12 Though a detailed description of each of these agents is beyond the scope of this article, an attempt is made to review the most significant agents or groups of agents which may be capable of inducing occupational asthma. The specific risk of developing occupational asthma is dependent on a variety of host factors and the nature and extent of occupational exposures. For example, workers in an isocyanate manufacturing plant have an approximate 5% risk of developing occupational asthma, and workers in high-exposure areas have the greatest risk.4, 5 At the other end of the spectrum, platinum refinery workers have been reported to develop occupational asthma at an alarming rate of up to 25%27 with even more of these patients developing platinum-specific antibodies. Regardless of the occupation, because occupational asthma can be associated with significant morbidity, early recognition and detection of a symptomatic worker is critical. Timely removal of an affected individual from the workplace can result in complete resolution of asthma, whereas chronic exposure may lead to persistent asthma despite removal from the offending exposure.