BIOMONITORING OF WORKERS EXPOSED TO 4,4'-METHYLENEDIANILINE OR 4,4'-METHYLENEDIPHENYL DIISOCYANATE

4,4'-Methylenedianiline (MDA) and 4,4'-methylenediphenyl diisocyanate (MDI) are important intermediates in the production of polyurethanes. In order to biomonitor people exposed to low levels of MDA or MDI we h ave developed sensitive methods to measure hemoglobin (Hb) adducts and urine metabolites. Adducts and metabolites from 33 workers exposed to MDA and 27 workers exposed to MDI were analyzed by gas chromatography -mass spectrometry after hydrolysis, extraction and derivatization wit h heptafluorobutyric anhydride. Hb adducts of MDA were detected in 31 out of the 33 MDA workers and both MDA and N-acetyl-MDA (AcMDA) were f ound in 20 of these individuals. The detection limit for MDA was 20 fm ol and for AcMDA 100 fmol/sample, which correspond to an absolute dete ction limit of similar to 1 fmol MDA and 5 fmol AcMDA, respectively. I n the urine of workers exposed to. MDA both MDA and AcMDA were found i n all samples, with the exception of five where only MDA was detected, Acid hydrolysis of the urine samples yielded an similar to 3-fold hig her concentration of MDA than the sum of MDA and AcMDA found after bas e hydrolysis. MDA but not AcMDA found in urine and in Hb correlate wel l, except for three outliers. In one workers the Hb adduct level of MD A was very low compared to the urine levels. Two workers had very high levels of MDA as Hb adducts but very low levels as urine metabolites. The former case indicates that the workers were recently exposed to h igher levels of MDA. The latter case suggests a relatively low recent exposure. The air levels of MDA, monitored using personal air monitors , were below the detection limit. It was possible, however, to determi ne exposure to MDA for all workers with the methods presented in this publication, Workers exposed exclusively to MDI were studied. Exposure levels, as monitored using personal air samplers, were below the dete ction limit of 3 mu g/m(3), with the exception of three individuals. I n 10 of the MDI workers, hydrolyzable Hb adducts of MDA (57-219 fmol/g Hb) were found. Except for four subjects, the presence of MDA (0.007- 0.14 nmol/l) and AcMDA (0.08-3 nmol/l) was detected in all urine sampl es after base treatment. Following acid hydrolysis of the urine, highe r levels of MDA (0.7-10 nmol/l) were found than the sum of free MDA an d AcMDA. According to the present data, it was possible to detect expo sure to MDI in a greater number of individuals by analyzing urinary me tabolites than by measuring Hb adducts or air monitoring.