OCCUPATIONAL ASTHMA DUE TO WESTERN OR CANADIAN RED CEDAR (THUJA PLICATA)

Abstract

A case is described to illustrate the clinical features of occupational asthma due to the inhalation of the dust of Western red cedar (Thuja plicata). The diagnosis was delayed, as the temporal relationship between symptoms and exposure to the dust was obscured. This happened because the symptoms had a delayed onset, rarely occurring at work; they appeared regularly on Saturday evenings and persisted for several weeks after cessation of exposure. The results of skin tests showed an immediate reaction to an extract of the dust, and bronchial provocation tests revealed both an immediate reaction and a reaction delayed for six hours, with a subsequent reaction 24 hours later again. Some features of the history, the response to aerosol challenge and the results of serial measurements of ventilatory capacity during a working week suggest that the clinical picture is influenced by the normal Increase in bronchial reactivity which occurs at night.