Effects of chronic exposure to diisocyanates

The pulmonary effects of chronic exposure to isocyanates (mainly MDI) at low levels (less than 0.02 ppm) were studied in a five year longitudinal survey of workers from two factories producing polyurethane foam. A respiratory questionnaire, flow volume curves and a single breath CO diffusion test were done at the beginning of the survey and repeated five years later; 318 workers (214 men, 104 women) of whom 83 (group I) were unexposed, 117 indirectly exposed (group II) and 118 directly exposed to isocyanates (group III) were examined. Five years later, half of the initial cohort only was still active and re-examined. The longitudinal analysis distinguished unexposed workers at both examinations (group A), indirectly at both examinations (group. B), directly exposed at both examinations (group. C) and workers exposed directly at first examination and retired from risk at the second (group. D). The decline of VC and FEV1 was not significantly different between exposed and unexposed. On the contrary, DLCO declined significantly in group C compared to the others. The results indicate that even at 'safe levels', chronic exposure to isocyanates involved a respiratory risk.