Toluene diisocyanate skin toxicity

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. 

Because of its high toxicity, carcinogenicity, and ability to cause sensitization, toluene diisocyanate should be handled using the "basic prudent practices" of Chapter 5.C, supplemented by the additional precautions for work with compounds of high toxicity (Chapter 5.D). In particular, work with TDI should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. 

Example 5. Toluene diisocyanate (TDI) has an LD50 (rat, oral) = 2060 mg/kg, which places it in HC 5 with regard to ingested toxicity. However, the LC50 (various animals) = 0.06-0.35 mg/L (4 h), which places it in HC 1 for inhaled toxicity. Furthermore, it is described as a powerful irritant to eyes, skin, and the respiratory tract, which places it in HC 1 for skin corrosive, respiratory sensitizer, and eye damage. Clearly, many precautions must be taken when working with TDI. 

Toluene diisocyanate is regulated by the Department of Transportation (DOT) as a Packaging Group II Toxic. Since TDI can cause serious injury to the lungs, eyes, and skin, all persons near the unloading site must wear protective clothing and equipment. They must observe the safe handling procedures and practices... 

Toluene-2,4-diisocyanate is a highly toxic compound by inhalation, a skin and eye irritant, and a carcinogenic substance. Exposure to its vapors can cause tracheobronchitis, pulmonary edema, hemorrhage, and death. The target organs are the respiratory system and skin. The toxic effects were also noted in the liver, kidney, and gastrointestinal tract. 

MDI is an eye and skin irritant. Contact with skin can produce eczema. The acute oral toxicity of this compound is very low, considerably lower than that of toluene-2,4-diisocyanate. The lethal dose for rats was... 

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