Late asthmatic reaction caused by naphthylene-1,5 diisocyanate

After occupational exposure to napthylene-1,5 diisocyanate (NDI) for 2 year s, a 33-year-old female worker developed work-related asthma attacks. Occup ational-type exposure tests with NDI resulted in a late asthmatic response, whereas a corresponding challenge test with 4,4'-methylenediphenyl diisocy anate was negative. We conclude that NDI exposure in the range of its occup ational exposure limit caused occupational asthma in this subject.