Isocyanates are major chemical commodities used in various applications including polyurethane paints and polyurethane foam structural components. Recently, there has been increasing interest in the contribution of dermal exposure to isocyanate-induced occupational disease. The isocyanates are among the most potent sensitizing agents found in the workplace environment and are known to cause contact dermatitis through both immunologic and irritant mechanisms, as well as occupational respiratory diseases, especially asthma and to a lesser extent, hypersensitivity pneumonitis. Furthermore, while it has long been assumed that isocyanate-induced respiratory disease is elicited by inhalation exposure, there is some concern that dermal exposure may play a role in the induction of respiratory sensitivity. This concern originated from the results of various animal experiments in which the epicutaneous application of isocyanate has resulted in the induction of respiratory sensitivity to isocyanate. Yet there is little information available on the extent, nature, and significance of workplace surface contamination by isocyanate and resulting dermal exposure of workers.

In this work, a new method for quantitative assessment of surface contamination by total reactive isocyanate group (TRIG) is being developed and an existing, commercially available qualitative colorimetric surface test kit for isocyanates (SWYPE[TM]) is being evaluated. The quantitative surface sampling method is based on an existing air sampling method for TRIG that uses MAMA reagent with HPLC analysis (Rando, et al, J. Liquid Chrom., 18:2743, 1995) and utilizes Pallflex filters for wipe collection of surface isocyanate contamination. Preliminary testing of the method in the laboratory has been done for TDI, HDI, and MDI on various surfaces at loadings ranging from 0.1 to 10 µg/cm². Recovery of isocyanate in these tests has ranged from none detected to approximately 70%, with efficiency improving with higher loading and smoother surfaces.

Detailed characterization of the performance of the method will be completed in the laboratory and followed by field evaluation of the technique. Demonstration of the method as an assessment tool and as an aid in training of workers is planned in pilot studies at an aerospace facility using polyurethane foam insulation materials and in autobody repair shops that use polyurethane paints. Preliminary qualitative examination of surface contamination at these sites with the SWYPE[TM]samplers has indicated no detectable surface contamination in the aerospace facility, whereas in the autobody shops, approximately 36% of samples have been positive, with contamination commonly found on spraybooth door handles and paint mixing benchtops.