Isocyanates, the ingredients of PU products, which are widely used in the car industry, have been confirmed to cause respiratory disease and asthma. This study aimed to investigate the formation of isocyanates in car repair factories and exposure levels for workers, and compare the sampling efficiencies of two different samplers.

Three car repair factories in Taipei city were chosen in this study, and the sampling sites were set in the painting and grinding districts of these factories. 2,4-TDI, 2,6-TDI, MDI, HDI and HDI-BT were collected by 2-piece (closed) filter cassette with inner wraparound filters and 2-piece (closed) filter cassette with double filters, which loaded glass-fiber fibers coated by 9-(N-methylaminomethyl) anthracene (MAMA). After derivatization, samples were analyzed by high performance liquid chromatography (HPLC) with fluorescence detector.

Field sampling in car repair factories showed the efficiency of 2-piece (closed) filter cassette with inner wraparound filters was better than that of others. The highest concentrations of HDI, 2,4-TDI, 2,6-TDI and MDI in painting districts were 9.72μg/m³, 55.76μg/m³, 4.09μg/m³ and 12.02μg/m³, respectively. These all appeared in factory A. But the highest concentration of HDI-BT existed in factory B, as 31.20μg/m³. In grinding district in factory A, the highest concentrations of HDI, 2,4-TDI, 2,6-TDI, MDI and HDI-BT were 4.81μg/m³, 6.17μg/m³, 2.01μg/m³, 5.78μg/m³ and 11.32μg/m³, respectively. Furthermore, HDI, 2,4-TDI, and 2,6-TDI mainly existed as gas in both operating districts while aerosol were the predominant type of MDI and HDI-BT. Obviously, in car repair factories, the isocyantes were existed as gas and aerosol simultaneously.

This study confirmed that 2-piece (closed) filter cassette with inner wraparound filters performed the best capture capability, however, it could not separate gas and aerosol type of isocynates. 2-piece (closed) filter cassette with double filters could separate gas and aerosol isocynates, but it would greatly underestimate the aerosol isocynates at high flow rate, high moisture, and long sampling time. Therefore, this investigation suggested using the 2-piece (closed) filter cassette with inner wraparound filters and the 2-piece (closed) filter cassette with double filters simultaneously might reflect the real situation when the sampling time was short as possible.