Isocyanates, organic health hazard

Fully cured polyurethanes present no health hazard they are chemically inert and insoluble in water and most organic solvents. Dust can be generated in fabrication, and inhalation of the dust should be avoided. Polyether-based polyurethanes are not degraded in the human body, and are therefore used in biomedical applications. Some of the chemicals used in the production of polyurethanes, such as the highly reactive isocyanates and tertiary amine catalysts, must be handled with caution. The other polyurethane ingredients, polyols and surfactants, are relatively inert materials having low toxicity. 

Isocyanates are volatile organic compounds widely used in industry for products such as printing inks, adhesives, two-pack paints (particularly in vehicle body shops) and in the manufacture of plastics (polyurethane products). They are irritants and sensitizers. Inflammation of the nasal passages, the throat and bronchitis are typical reactions to many isocyanates. When a person becomes sensitized to an isocyanate, very small amounts of the substance often provoke a serious reaction similar to an extreme asthma attack. Isocyanates also present a health hazard to fire fighters. They are subject to a workplace exposure limit (WEL) and respiratory protective equipment should normally be worn. Two-pack polyurethane paints and varnishes are used in construction as surface coatings. 

Health and Safety Executive Health and Safety Laboratory, MDHS 25/3. Methods For the Determination of Hazardous Substances Organic Isocyanates in Air, Health and Safety Executive/ Occupational Safety and Hygiene Laboratory, Sheffield, 1999. 

Hazardous Decomp. Prods. Heated to decomp, emits CO, CO2, NOx, ammonia, traces of organic compds. inc. hydrogen cyanide, nitriles, isocyanates, nitrosamines, amines NFPA Health 3, Flammability 4, Reactivity 0 Uses Intermediate in organic synthesis intermediate for water-gel explosives, accelerators, pharmaceuticals, insecticides, N-methylpyrrolidine, methylalkanolamines, surface active agents, fungicides in tanning component of photographic developers and paint removers fuel additive prod, of dyes polymerization inhibitor rocket propellant See also Methylamine... 

Most of the listed exposure limits refer to single substances or closely related groups, e.g. cadmium and compounds, isocyanates etc. A few exposure limits refer to complex mixtures or compounds, e.g. white spirit, rubber fume. However, exposure in workplaces is often to a mixture of substances and such combinations may, by their nature, increase the hazard. Mixed exposure requires assessment with regard to possible health effects, which should take into account other factors such as the primary target organs of the major contaminants and possible interaction between the latter substances. 

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