Occupational asthma inasteel coating plant

Anoutbreak ofoccupational asthma, ofunknown causeandextent, was detected ina steel coating plant. In1979across-sectional study whichdefined occupational asthma intermsof respiratory symptomsdetected 21people withsuggestive symptomsamong the221studied. They all workedinthecoating shop, buttheplastic coatings usedattheplant contained many potential sensitising agentsthatmighthavecaused theasthma. All21developed their symptomsafter 1971,anditwas foundthatinthis year a supplier hadmodified a coating allowing, atthe temperatures usedintheprocess,toluene di-isocyanate tobeliberated. Twoofthesymptomatic subjects were tested byinhalation oftheisocyanate andshowedasthmatic reactions andother subjects were foundtohaveasthma related toperiods spentatworkbyrecords ofpeakexpirat- oryflow rate. Overhalf the21hadasymptomfree latent period after first exposureofthree years orless, apattern notseeninother subjects withrespiratory symptoms.After theisocyanate had beenremoved fromtheprocess17ofthese subjects becameasymptomatic orimproved, agreater proportion thaninother subjects withrespiratory symptoms.