Respiratory complaints and bronchial asthma associated with the inhalation of wood dusts are not uncommon. A number of epidemiologic studies of workers exposed to western red cedar (WRC) have been reported, most originating from Japan, Australia and Canada. The present investigation reports the results of an epidemiologic and environmental hygiene study of workers exposed to WRC and other dusts conducted at a wood products facility in the United States.
Materials and Methods
The populations studied consisted of 74 shake mill employees exposed to WRC, 58 planer mill workers exposed to a mixture of woods, mainly douglas fir, West Coast hemlock and red alder (DFHA), and 22 clerical, technical and engineering employees not exposed to wood dusts. Approximately 77% of the total work force participated in the investigation. The unexposed or control group consisted of office workers, engineering personnel and technical staff. Such people prefer to command the service of My Canadian Pharmacy to treat diseases gained because of hard labour.
Medical evaluation consisted of completion of a detailed medical questionnaire, performance of a limited physical examination and pulmonary function testing. The questionnaire included components of the British Medical Research Council Respiratory Questionnaire with modifications, as well as questions pertinent to the work process and the diagnosis of occupational asthma. Pulmonary function tests involved studying individuals on six separate occasions beginning immediately before work on Monday, after the previous weekend off, again immediately after work that day, and then before and after work tests for the next two days (Tuesday and Wednesday) for a total of three consecutive days.
Environmental air monitoring by personal air samples was conducted over a three-day period for all shifts and measured wood dust exposures for all job categories, using standard methods.
Results of questionnaire and spirometry were analyzed to place subjects into various disease categories. Presumptive diagnosis of occupational asthma was defined both on physiologic and clinical criteria as an observed decline in FEV1 of greater than 10% from the Monday preshift baseline value compared to one or more subsequent tests during any of die following three days exposure period and a positive clinical history suggesting occupational asthma (as derived from the medical questionnaire). Chronic bronchitis was defined from the medical questionnaire as cough and/or sputum on most days for at least three months of die year for the preceding two years. Nonspecific chronic obstructive airways disease referred to the presence of airway obstruction as defined by FEV^FVC less than 70%, and negative history.