CANCER INCIDENCE AND MORTALITY IN THE SWEDISH POLYURETHANE FOAM MANUFACTURING-INDUSTRY

Toluene diisocyanate (TDI) and methylene diphenyldiisocyanate (MDI) ar e used in large quantities in the polyurethane foam manufacturing indu stry. Both substances are mutagenic and at least TDI is carcinogenic t o animals, but the occupational hazard with respect to cancer is not k nown. Cancer incidence and mortality patterns were therefore investiga ted in a cohort of 4154 workers from nine Swedish plants manufacturing polyurethane foam, employed for at least one year. Each workplace and job task in the nine plants was categorically assessed for each calen dar year by an experienced occupational hygienist, for ''no exposure'' , ''low or intermittent exposure'', or ''apparent exposure'' to TDI an d MDI. The observed deficit for all cause mortality (standardised mort ality ratio (SMR) 0.78, (95% confidence interval (95% CI) 0.66-0.93) b ecame smaller (SMR 0.92) excluding the first 10 years since the start of exposure and was ascribed to a healthy worker effect. No increased risk for death from bronchial obstructive diseases was found. An almos t statistically significant deficit occurred for all malignant neoplas ms (standardised incidence ratio (SIR) 0.81, 95% CI 0.63-1.02); slight (not significant) increased risks were found for rectal cancer (SIR 1 .66) and non-Hodgkin's lymphoma (SIR 1.53). The SIR for non-Hodgkin's lymphoma increased to 2.80 (95% CI 0.76-7.16) when the first 10 since first exposure were excluded from the observation period. The correspo nding figure for rectal cancer was 1.92 (95% CI 0.S2-4.92). Further re stricting the analysis to those who had experienced an apparent exposu re to TDI or MDI increased the SIR for both rectal cancer (3.19, 95% C I 0-66-9.33), and non-Hodgkin's lymphoma (3.03, 95% CI 0.37-10-9). The se estimates were based, however, on few incident cases. As the cohort is still young and little time has elapsed since the start of exposur e, future follow ups will enable a more conclusive evaluation.