Diisocyanates, also referred to as isocyanates, are organic compounds with two isocyanate groups (-NCO). They are used to make polyurethane coatings and rigid and flexible foams. Isocyanates are the leading cause of occupational asthma in many post-industrial countries where incidence rates have been measured. Commonly used isocyanates are toluene diisocyanate (TDI), methylene diphenyl diisocyanate (MDI) and polymethylene polyphenyl isocyanate (PAPI). [LaDou, p. 372; LaDou (2nd ed.), p. 521-3] Exposure can occur to vapors at room temperature (TDI and HDI), or after heating (MDI and PAPI), or during spraying processes (all isocyanates). [Sullivan, p. 470-2] "Isocyanate HP," a form of hypersensitivity pneumonitis, has been reported. [Rosenstock, p. 346] Diisocyanates can also cause contact dermatitis (Type IV). [PMID 22411214
] "Isocyanates and Work-Related Asthma: Findings from California, Massachusetts, Michigan, and New Jersey, 1993-2008." [PMID 26351141
] See "MONOISOCYANATES."