[Diseases caused by diisocyanates. 1. Irritation of the respiratory system and skin].

Toluylene diisocyanate (TDI) has an uncommon importance in the production of irritation of respiratory system. In the last few years less volatile isocyanate compounds have been substituted for TDI. Commercial available diphenylmethane diisocyanate (MDI) and polymethylene polyphenyl isocyanate (PAPI) were analyzed in 1971. The analysis indicated the presence of 21% TDI in several samples. It is evident, with respect to the relatively high vapor pressure of TDI, that such impurities will be able to cause air concentrations in excess of the current threshold limit value (TLV) of 0.02 ppm. Liberation of TDI by heat from varnish insulinations is a difficult problem. This problem was described as "an old hazard in new guise". Especially, in a soldering process on polyurethane coated wire, excess of TLV is possible in unfavourable conditions. By the regulation that the concentration of TLV must not exceed 0.02 ppm and by the use of new non-volatile isocyanate the risk of acute and subacute intoxications has considerably subsided. Chronic irritations of respiratory system and asthma-like diseases, however represent still an unsolved problem.