Toluene diisocyanate respiratory sensitization

Toluene diisocyanates are potent respiratory irritants and sensitizers, even at low air-... 

No deterioration of lung function, but an increased frequency of respiratory symptoms were observed in a follow-up study among non-sensitized workers with a mean exposure to toluene diisocyanates of 3 ppb [21.3 J,g/m (Omae et al., 1992a). This study also suggested that among workers with a mean exposure of 8 ppb [57 pg/m ], peak exposures to 30 ppb [213 pg/ni ] and above were associated with a loss of ventilatory function among employees not sensitized to toluene diisocyanates (Omae et al., 1992b). 

Inhalation exposure to toluene diisocyanates is irritating to the eyes and respiratory tract, and induced chronic rhinitis, interstitial pneumonia and catarrhal bronchitis after long-term exposure. Respiratory sensitization to toluene diisocyanate developed in guinea-pigs after inhalation but also after dermal exposure (lARC, 1986). 

Toluene diisocyanates are metabolized to toluene diamines in humans and rats. Toluene diisocyanates are irritants and respiratory sensitizers in humans and rats. 

Huang, J., Aoyama, K. Ueda, A. (1993) Experimental study on respiratory sensitivity to inhaled toluene diisocyanate. Arch. Toxicol., (>1. 373-378... 

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 ... 

Sensitizer. A chemical that causes vulnerable, exposed individuals to develop a respiratory allergic reaction following repeated exposure. Methylene bisphenyl isocyanate, toluene diisocyanate, and trimellitic anhydride are examples of respiratory sensitizers. It should be noted that sensitizing chemicals that are inhaled have the propensity to also induce dermal sensitization and that skin exposure to sensitizers (e.g., ammonium thioglycolate) can induce respiratory sensitization. Such cross-sensitization is discussed below and in Chapter 29. 

Inhalation of sensitizing chemicals can lead to dermal sensitization, and dermal absorption of sensitizing chemicals can lead to respiratory sensitization. Airway exposure to toluene diisocyanate has been shown to induce dermal sensitization, I23l and dermal application of trimellitic anhydride has been shown to induce respiratory sensitization in test animalsJ24-26 These results are consistent with the understanding that both respiratory and dermal sensitization are associated with IgE responses. 

The reverse phenomenon has also been demonstrated. Isolated airway exposure to toluene diisocyanate, a powerful respiratory sensitizer, has been demonstrated to cause skin sensitization. I37l These crossovers are believed to be due to the observation that both dermal and respiratory sensitization result in increased serum IgE antibody levels J3133 and point out the dangers associated with exposures to sensitizing chemicals. 

FABBRI, L.M., DANIELI, D CRESCIOLI, S BEVILACQUA, P MELI, S SAETTA, M. MAPP, C.E. (1988) Fatal asthma in a toluene diisocyanate sensitized subject. American Review of Respiratory Disease, 137, 1494-1498. 

Respiratory sensitizer May cause allergy or asthma symptoms or breathing difficulties if inhaled 1 Danger Human evidence of respiratory hypersensitivity, tmd/or positive from animal testing Polyisocyanates, such as toluene diisocyanate acid anhydrides, such as tiimellitic anhydride, formaldehyde... 

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. 

Urethane resins may contain free diisocyanates, which are usually respiratory irritants and sensitizers that have caused rhinitis and asthma (Estlander et al. 1992). 2,4-toluene diisocyanate (TDI) and hexamethylene diisocyanate (HDI) are important respiratory sensitizers, whereas 4,4 -diphenylmethane diisocyanate (MDI) is the most important skin sensitizing diisocyanate (Estlander et al. 1992). Two-component systems in which addition of a diisocyanate to the polyhydroxyl compound immediately before use carry the greatest risk of skin sensitization. Partial polymerization of diisocyanates to increase molecular weight and reduce volatility are used to decrease the risk of sensititization (Mathias 1984). See also the chapter on polyurethane resins in this book. 

Toxicology. Toluene-2,4-diisocyanate (TDI) is a strong irritant of the eyes, mucous membranes, and skin and is a potent sensitizer of the respiratory tract. 

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