Histamine release by Western red cedar (Thuja plicata) from lung tissue in vitro.

28-30. Various respiratory symptoms have previously been observed in workers exposed to dust from Western red cedar (). Although an allergic basis for these effects has been proposed, the possibility that the dust may contain a pharmacologically active agent was investigated. Aqueous extracts of two samples of red cedar released significant amounts of histamine from pig and human lung . For one of these samples, using pig lung, a dose-response relation was found over a narrow range of concentrations. These dusts possessed the same order of histamine-releasing activity as a sample of cotton dust. Potassium cyanide reduced the release of histamine caused by low concentrations of Western red cedar. Similar effects of cyanide on the histamine-releasing activity of cotton dust and compound 48/80 were observed. It is possible that release of histamine in the lungs and upper respiratory tract occurs on inhalation of dust from Western red cedar and this may be a contributory factor to the development of respiratory symptoms in workers exposed to the dust of this wood.