Western Red Cedar (Thuja plicata) and Other Wood Dusts

Exposure towood dust is a common occurrence in all countries because of its traditional use as fuel and in constructions for human habitation. Exposure to wood dusts can cause contact dermatitis and cancer of the nasopharynx. Respiratory illnesses associated with exposure to wood dust include asthma, hypersensitivity pneumonitis, organic dust toxic syndrome, chronic bronchitis, and mucous membrane irritation syndrome (1,2). Inmost instances respiratory illness is caused by exposure to chemical compounds in the wood dust. For many types of wood dust, the nature of the responsible chemical compound remains unknown; in others, the disease is caused by exposure to the molds or bacteria growing on the wood chips, bark, or bonding materials used in the wood strips or boards. By far, the most common respiratory illness reported from wood dust exposure is asthma. The disease usually arises as a result of occupational exposure, although in some individuals it may result from exposure in their hobby. Many different species of wood have been identified as being associated with occupational asthma. They are often highly prized for durability and quality of appearance. The extent to which they are used in construction and furniture industries is not known. Most cases of occupational asthma caused by wood dusts were published as case reports, except that caused by western red cedar (WRC) (Thuja plicata). Occupational asthma caused by WRC has been studied extensively because it affects a vast number of workers in the primary industries of the West coast of North America and in countries where red cedar is exported. For this reason, western red cedar asthma (WRCA) will be discussed in detail first.