Respiratory and other hazards of isocyanates

Abstract

Isocyanates are increasingly being used for manufacturing polyurethane foam, elastomers, adhesives, paints, coatings, insecticides, and many other products. At present, they are regarded as one of the main causes of occupational asthma. The large number of workers who are exposed to these chemicals have a concentration-dependent risk of developing chronic airway disorders, especially bronchial asthma. Different pathophysiologic mechanisms are involved. Immunoglobulin E (IgE)-mediated sensitization and irritative effects have been clearly demonstrated in both exposed subjects and animals. Presumably, neural inflammation due to neuropeptide release of capsaicin-sensitive afferent nerves is crucial. We collected data on 1780 isocyanate workers who had been examined by our groups. Of them 1095 (including subjects from outpatient departments) had work-related symptoms, predominantly of the respiratory tract. Specific IgE antibodies were found in 14% of the 1095 subjects. The methacholine challenge test was shown to be an inadequate predictor of the results of inhalative isocyanate provocation tests in workers and in asthmatic controls. Isocyanate (toluene diisocyanate TDI) air concentrations of 10 ppb (0.07 mg/m3) and 20 ppb (0.14 mg/m3), respectively, did not cause significant bronchial obstruction in the majority of previously unexposed asthmatics with bronchial hyperreactivity. IgG-mediated allergic alveolitis, a rare disease among isocyanate workers, was found in approximately 1% of the symptomatic subjects. Experimental studies exhibit dose-dependent toxic effects and give evidence for tachykinin-mediated bronchial hyperreactivity after exposure to isocyanates. The clinical role of genotoxic effects of isocyanates and their by-products demonstrated here in vitro and in vivo has yet to be clarified.

Eye and airway symptoms in low occupational exposure to toluene diisocyanate

“…Apart from asthma, symptoms such as cough, wheezing, and dyspnea are commonly reported (1)(2)(3)(4). Other effects are hypersensitivity pneumonitis and an accelerated decline of lung function (2,(5)(6)(7).…”

Biological monitoring of exposure to toluene diisocyanate

“…TDI is a respiratory irritant and may also cause chronic disorders of the airways, such as occupational asthma (2)(3)(4), and, hence, it is essential to monitor the occupational exposure for workers. Such surveillance has mainly been performed by air monitoring.…”

In silico docking of methyl isocyanate (MIC) and its hydrolytic product (1, 3-dimethylurea) shows significant interaction with DNA Methyltransferase 1 suggests cancer risk in Bhopal-Gas-Tragedy survivors

“…Exposure to MIC causes several respiratory disorders and chronic obstructive pulmonary disease (COPD) (Vandenplas et al, 1993;Baur et al, 1994;De, 2012;2013). Besides, the immunotoxic (Karol et al, 1987), genotoxic (Conner et al, 1987;Tice et al, 1987), reproductive and developmental toxic effects (Schwetz et al, 1987) are well-documented in humans and animals.…”