NONSPECIFIC BRONCHIAL HYPER-REACTIVITY AFTER EXPOSURE TO WESTERN RED CEDAR

Abstract

A 55 yr old non-atopic man presented with a 2 yr history of progressively severe conjunctivitis, rhinitis, and asthma related to exposure to freshly cut red cedar. Chest roentgenogram, lung volumes, diffusing capacity for carbon monoxide, and expiratory flow rates were normal. A histamine inhalation test demonstrated mild, nonspecific bronchial hyperreactivity. After a 35-min cumulative exposure to Western Red Cedar [Thuja plicata] sawdust in the laboratory, the patient developed a late asthmatic response. Bronchial reactivity to inhaled histamine increased significantly after exposure to red cedar in the laboratory and again after natural exposure to red cedar at work. On both occasions forced expiratory volume in 1 s [FEV1] was decreased when compared to control values. Exposure to red cedar sawdust for 15 min was repeated in the laboratory and histamine inhalation tests were performed the day before, for 4 consecutive days after and 11 days after exposure. Before each test, FEV1, lung volumes, specific conductance, maximal expiratory flow rates at 25 and 50% of vital capacity, closing capacity, and the slope of phase III from the single-breath O2 test were measured. Six h after exposure to cedar, all measurements documented significant airway obstruction that persisted until the 2nd day. Bronchial responsiveness to inhaled histamine increased on the first 2 days after exposure to cedar, but this increase persisted on the 3rd and 4th day when all other pulmonary function tests had returned to control values. Eleven days later, the bronchial hyperreactivity to inhaled histamine returned to control values. In a sensitized subject, exposure to Western Red Cedar induced a transient increase in nonspecific bronchial reactivity that was present in the absence of airflow obstruction. Factors other than decreased airway caliber are probably important in this phenomenon.