Toluene diisocyanate health hazards

Isoouanates. Various isocyanates are employed in the polymer industry. These compounds are powerful irritants and they are highly toxic. Of particular interest are methylene-di-paraphenylene isocyanate (MDI) and toluene-2,4-diisocyanate (TDI). Various alkyl isocyanates (e.g., methyl, ethyl, propyl, butyl, and cyclohexyl) derivatives may also be of current interest with respect to potential occupational health hazards. Simultaneous analysis of MDI and TDI by HPLC has been accomplished by a modification of the method of Dunlap et al. (28). Air samples are collected in impingers containing p-nitrobenzyl-n-... 

The toxic route is primarily inhalation. The vapor pressure of this compound at ambient temperature is very low, 0.00014 torr at 25°C. However, when heated to about 75°C, the acute health hazard is greatly enhanced (Hadengue and Philbert 1983). The acute toxic symptoms were found to be similar to those of toluene-2,4-diisocyanate and other aromatic isocyanates. Inhalation of its vapors or particulates can cause bronchitis, coughing, fever, and an asthma-like syndrome. Other symptoms were nausea, shortness of breath, chest pain, insomnia, and irritation of the eyes, nose, and throat. The immunologic response, however, varied among humans. Exposure to 0.1-0.2 ppm for 30 minutes is likely to manifest the acute toxic effects in humans. 

PU are compounds formed by reacting the polyol component with an isocyanate compound, typically toluene diisocyanate (TDI) methylene diisocyanate (MDI) or hexamethylene diisocyanate. Polyols are relatively non-toxic (i.e., polyether type polyols are found to be safe, because they are low in oral toxicity with almost no irritation effect to the eyes and skin), however, isocyanates are highly toxic and the product can have a significant toxicity if remnants of isocyanate are in it, which manifests itself mainly as a respiratory (as well as a dermal) hazard. Exposure to the vapour of isocyanates directly may cause irritation for the eyes, respiratory tract and skin. Such an irritation may be too severe to produce bronchitis and pulmonary oedema. As health hazards of isocyanates are considered, one immediately remembers one of the worst industrial disasters of the 20th century, that occurred in Bhopal, India, because of the toxic cloud of methyl isocyanate was released accidentally from the Union Carbide pesticide factory in December 1984. An estimated 3,000 people died immediately with a final of some 20,000, most suffocating from the cloud s toxic chemicals, and some 50,000 were injured, most were residents living near the plant. 

CAUTION The handling of isocyanates should be done with great care because of their known toxicity hazard. The hazards and chemistry of methyl isocyanate have recently been reported. Toluene diisocyanate (TDI), methylene diisocyanate (MDI), and methyl isocyanate (MIC) are flammable, very reactive, and have in common low maximum allowable concentrations for employee exposure by the Occupational Safety and Health Administration (OSHA). 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ ]

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