EPIDEMIC OF ASTHMA IN A WOOD PRODUCTS PLANT USING METHYLENE DIPHENYL DIISOCYANATE

Eighteen employees with lower respiratory symptoms later confirmed to be occupational asthma were referred for evaluation. All were employee s of a single wood products plant using heated methylene diphenyl diis ocyanate (MDI) in the manufacture of a synthetic wood product. Of the 18, 15 had no prior airway symptoms or other known bronchial injury, a nd 16 had positive methacholine bronchial provocation tests. All cases occurred during a 2.5-year period after exposure to a new manufacturi ng process using steam-heated MDI resin in a new manufacturing facilit y. Initially, employees developed symptoms related to the start-up pro cess in the plant, with possible higher MDI exposures and probable hig her resin temperatures. Later, most employees who developed new sympto ms worked in areas of the plant where they were exposed mostly to heat ed boards. This suggests MD1 sensitization arising at lower temperatur es than previously considered likely for this substance. (C) 1997 Wile y-Liss, Inc