Sensory irritation by toluene diisocyanate in single and repeated exposures

The effects of single and repeated exposures to toluene diisocyanate (TDI) at concentrations ranging from 0.007 to 2 ppm were investigated using an animal model to detect the level of sensory irritation caused by this chemical. Time-response relationships showed the slow development of the response with exposure duration and a very slow recovery following 3 hr of exposure. Concentration-response relationships also showed that the level of response was not only dependent upon exposure concentration, but also on duration of exposure and that TDI is the most potent sensory irritant tested so far. Repeated exposures to TDI at or above 0.023 ppm resulted in cumulative effects. On the basis of a prior prediction proposed from the results obtained with this animal model, it is suggested that the Threshold Limit Value (TLV) for industrial exposure be reduced to 0.006 ppm as a time weighted average (TWA) and no exposure above 0.02 ppm be permitted, even for short exposures.