Isocyanates - assessment of human exposure

Abstract: Isocyanates are used mainly for manufacturing of polyurethane (PUR) foams, lacquers, elastomers and glues. The production of PUR exceeds 2 million tonnes per year and is increasing. Occupational exposure to isocyanates are associated with respiratory disorders. A method based on liquid chromatography mass spectrometry (LC-MS) was developed for the simultaneous determination of isocyanates, aminoisocyanates and amines in air. Sampling was performed in impinger flasks where the isocyanates were derivatised with di-n-butylamine (DBA) and in a subsequent step the amines with ethylchloroformate. The presence of possible interfering compounds did not affect the results. The method made it possible to qualitatively determine new isocyanate- and amine-containing compounds formed during thermal decomposition of PUR. A method based on 9-(N-methylaminomethyl)-anthracene impregnated filters was developed which made it possible to sample monomeric isocyanates during a prolonged time. A LC-MS method for the biological monitoring of hexamethylene diisocyanate and isophorone diisocyanate was developed and biomarkers were found in urine hydrolysates among three exposed volunteers. An association between the total excreted amount of biomarkers in hydrolysed urine and the estimated inhaled dose for three concentrations of the isocyanates was seen. The exposure to toluene diisocyanate at a plant producing flexible PUR foam was studied with a continuous air monitoring instrument. The exposure was found to be typically peak wise. Biomarkers in hydrolysed urine and plasma were determined using GC-MS. A relation in time between air levels of isocyanates and biomarkers in urine was seen but no correlation was found between biomarkers in urine and plasma and air concentrations of isocyanates.