BIOMARKERS OF EXPOSURE, ANTIBODIES, AND RESPIRATORY SYMPTOMS IN WORKERS HEATING POLYURETHANE GLUE

Objectives-The pathogenic basis of respiratory disorders associated wi th isocyanates are still obscure. One reason for this is the lack of g ood estimates of human exposure. In this study exposure was estimated by measurement of isocyanate metabolites in biological samples. Method s-In a factory using isocyanate based polyurethane (PUR) glue, isocyan ate concentrations in air were measured by liquid chromatography. Samp les from 174 employees were analysed for metabolites of 4,4'-methylene diphenyl diisocyanate (MDI) in plasma (P-MDX) and urine (U-MDX). Afte r hydrolysis, 4,4'-methylenedianiline was measured by gas chromatograp hy-mass spectrometry (GC-MS). The employees were screened for work rel ated respiratory symptoms and tested for specific immunoglobulin E (Ig E) and IgG antibodies directed against isocyanate conjugated to human serum albumin. Results-The time weighted isocyanate concentrations in air were low (MDI< 0.2-7; hexamethylene diisocyanate (HDI) < 0.1-0.7; 2,6-toluene diisocyanate (TDI) < 0.1 mu g/m(3)). All subjects had dete ctable P-MDX and U-MDX. There were significant associations between th e estimates of exposure to thermal degradation products of an MDI base d glue and P-MDX (range less than or equal to 0.10-5.5 mu g/l), and U- MDX (less than or equal to 0.04-5.0 mu g/g creatinine); in cases of he avy exposure. P-MDX and U-MDX were associated with each other (r = 0.6 4; P = 0.0001), work related symptoms (P-MDX: P = 0.03; Mann-Whitney U test), and serum concentrations of MDI specific IgG antibodies (r = 0 .26; P = 0.0007). Unexpectedly, high P-MDX and U-MDX concentrations we re also encountered in workers cutting textile (P-MDX 2.4-4.5 mu g/l; U-MDX 0.81-3.8 mu g/g creatinine); the reason is still unknown. Equall y unexpected, there were significant negative associations between P-M DX and liver function tests. Conclusions-The results clearly show the value of biomarkers for isocyanate exposure; in particular, P-MDX is u seful. Further, these results show the risk connected with thermal deg radation of PUR.