Toluene 2,4-diisocyanate toxicity

NOTE - Petrochemical plants also generate significant amounts of solid wastes and sludges, some of which may be considered hazardous because of the presence of toxic organics and heavy metals. Spent caustic and other hazardous wastes may be generated in significant quantities examples are distillation residues associated with units handling acetaldehyde, acetonitrile, benzyl chloride, carbon tetrachloride, cumene, phthallic anhydride, nitrobenzene, methyl ethyl pyridine, toluene diisocyanate, trichloroethane, trichloroethylene, perchloro-ethylene, aniline, chlorobenzenes, dimethyl hydrazine, ethylene dibromide, toluenediamine, epichlorohydrin, ethyl chloride, ethylene dichloride, and vinyl chloride. 

Biodegradable poly(phosphoester-urethanes) containing bisglycophosphite as the chain extender were synthesized. Methylene bis-4-phenyl isocyanate (MDI) and toluene diisocyanate (TDI) were initially used as diisocyanates. Since there was a concern that the degradation products could be toxic, the ethyl 2,6-diisocyanatohexanoate (LDI) was synthesized and replaced the MDI (or TDI). The hydrolytic stability and solubility of these polymers were tested. Preliminary release studies of 5-fluorouracil from MDI based poly(phosphoester-urethane) and methotrexate from LDI based poly(phosphoester-urethane) are also reported. 

Two final examples of the sensitivity and general applicability of the FTIR gas analysis technique are illustrated in Fig. 8. Trace (A) shows the spectrum obtained from an ultra-air filled 70 liter sampling bag into which had been injected, 18 hours previously, 4.8 microliters of TDI, toluene diisocyanate. On the basis of the single feature at 2273 cm l, it is estimated that 50 ppb TDI could be detected. The lower Trace (B), shows the spectrum of nickel carbonyl. This highly toxic but unstable gas was found to decay rapidly at ppm concentrations in ultra air (50% lifetime 15 minutes). Calibration of its spectrum was established by recording successive spectra at ten minute intervals and by attributing the increase in carbon monoxide concentration (calibration known) to an equivalent but four times slower decrease in nickel carbonyl concentration. The spectrum shown represents 0.6 ppm of the material. Note the extraordinary absorption strength. The detection limit is thus less than 10 ppb. 

Duncan B, Scheel LD, Fairchild EJ, et al. 1962. Toluene diisocyanate inhalation toxicity pathology and mortality. Am Ind Hyg Assoc J 23 447-456. 

Luckenbach M, Kielar R. 1980. Toxic corneal epithelial edema from exposure to high atmospheric concentration of toluene diisocyanates. Am J Ophthalmol 90(5) 682-686. 

Isocyanates. These are highly toxic compounds, particularly toluene diisocyanate, which cause permanent lung damage on repeated exposure. Furthermore, over a period of time, the worker may become sensitised to isocyanates, such that subsequent undetectable concentrations produce severe symptoms. 

Ammoxidation is also used for the manufacture of isophthalonitrile from m-xylene. The catalysts claimed in the patents are mixed oxides, e.g., of Mo, V, and Sb. The dinitrile is hydrogenated to m-xylylene diamine and m-diamino-dimethylcyclohexane, used for the production of the corresponding diisocyanates that are less toxic than toluene diisocyanate TDL A different use is for the production of tetrachloroisophthalonitrile, a potent fungicide. 

U.S. Environmental Protection Agency. 1992. Technology transfer network air toxics Web site. 2,4-Toluene diisocyanate, hazard summary. Revised in January 2000 (updated 2007). Washington, D.C. U.S. Environmental Protection Agency. 

MIC is less frequently used than toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), and other isocyanates. In order to highhght the distinctiveness of MIC toxicity, the toxicity of diisocyanates is described briefly. 

Toluene diisocyanate has rapid linear absorption via inhalation with persistence in tissues at low levels for up to 2 weeks. Absorption of toluene diisocyanates by inhalation is reflected by high acute toxicity following such exposure. Little information is available on the distribution of toluene diisocyanates in mammals. Reaction of toluene diisocyanate with serum albumin yields protein conjugates. Toluene diisocyanate is hydrolyzed into 2,4-diaminotoluene in man. 

Toluene diisocyanate is a cross-linking agent and both a pulmonary and dermal sensitizer. Most toxicity occurs with repeated exposure. 

Wood stains and varnishes used indoors contain aliphatic and aromatic hydrocarbons, isocyanates, ketones, and esters. Though these have limited use compared with paint, newly finished building interiors often contain toxic levels of these. Toluene diisocyanate, used as a catalyst in polyurethane wood finishes, is a powerful respiratory irritant and sensitizer. 13 ... 

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