PULMONARY EFFECTS OF SIMULTANEOUS EXPOSURES TO MDI FORMALDEHYDE AND WOOD DUST ON WORKERS IN AN ORIENTED STRAND BOARD PLANT

A study was undertaken in a plant producing oriented strand board (OSB ) from aspen and balsam wood, bonded by methylene diisocyanate (MDI) a nd phenol formaldehyde. A group of 127 production workers in the plant was compared to 165 oil workers from the same geographic area. Measur ements of MDI ranged from 6 to 33 mu g/m(3) (0.001-0.003 ppm), of resp irable dust ranged from 0.05 to 0.5 mg/m(3), and of formaldehyde were 0.05 ppm or less. The ratio of forced expiratory volume in 1 second to forced vital capacity (FEV(1)/FVC) was significantly lower among the OSB workers compared to the oil workers, and this was more pronounced for ex-smokers and current smokers. A number of respiratory symptoms s uggestive of airway reactivity were significantly more common among th e OSB workers. It was known that changes to reduce worker exposure had been made in the plant before the study, and it is unclear whether th e health effects documented were the result of these low levels or if previous, probably higher levels were responsible.