1996 OPEN FORUM Abstracts
Asthma and the Workplace
William G. Hughson, MD Tuesday, November 5, 1996
Occupational asthma (OA) is causally related to exposure in the working environment to airborne dusts, gases, vapors, or fumes. While some definitions of OA require an immune-mediated sensitivity to a specific agent, the clinician must also consider non-specific irritants, since aggravation of pre-existing non-occupational asthma is usually compensable under Workers' Compensation. Accurate diagnosis of OA requires the clinician to understand the nature and degree of the workplace exposures, and to make a temporal association between the asthma and occupation. Given the inherent variability of asthma, and the fact that the patient may have early, late, dual, or recurrent-late onset of symptoms, diagnosis may be very difficult.
The proportion of all asthma due to occupation is estimated at 2 to 15%. The percentage of the workforce who develop asthma varies widely between occupations, and within industries at different levels of exposure. The true occurrence of OA is probably greater than reported in most series; those affected tend to leave the industry, and the "survivors" then demonstrate the "healthy worker effect" so common in most studies of employed individuals.
Routine tests such as chest radiographs and pulmonary function tests can identify impairment, but are non-specific for OA. Skin tests, serology, and inhalation challenge can assist in establishing a workplace etiology, but none of the tests are either sensitive or specific. The occupational history remains the most valuable diagnostic tool.