Workers were grouped with regard to their potential risk of TDI exposure (high, medium, low), based on their primary work location and duties, with the input of an industrial hygienist (JS) who had evaluated the plant. Workers who spent most of their time in the foaming hall, where foam was produced from raw materials including TDI were classified into the high exposure risk group; those who spent most of their time in the cutting area where foam blocks are cut to size after a period of curing, in the laboratory, where production samples are tested, and in maintenance were included in the medium exposure risk group, and the remaining workers, such as administrative, quality and warehouse, were included in the low exposure risk group.