Assessment of occupational exposure to 4,4'-methylenedianiline by the analysis of urine and blood samples.

Seven workers at a work site where methylenedianiline (MDA) was used as a curing agent for an epoxy resin were studied during 4 workdays and one weekend. Internal exposure was monitored by analysis of 4,4'-MDA in hydrolysed urine and blood. After acidic hydrolysis, MDA was extracted, derivatised by use of pentafluoropropionic anhydride, and determined by gas chromatography and mass spectrometry, with negative ion chemical ionization. There was wide variation of MDA concentrations in hydrolysed blood between the workers (range 10-60 nmol/l). Also, the urinary excretion rate varied considerably both between and within the individual workers (0-90 mumol/h). The urinary excretion displayed some variation in relation to exposed periods. The urinary levels were linearly related to the concentrations in blood (rs = 0.93, P = 0.02). The present results show the value of excretion of MDA in hydrolysed urine and concentrations in blood as means for the biological monitoring of MDA exposure. In this case, the exposure was probably mainly dermal, in spite of extensive protection measures.