Methyl Isocyanate Research Articles

Sequential Respiratory, Psychologic, and Immunologic Studies in Relation to Methyl Isocyanate Exposure over Two Years with Model Development

Of 113 methyl isocyanate (MIC)-exposed subjects studied initially at Bhopal, India, 79, 56, 68, and 87 were followed with clinical, lung function, radiographic, and immunologic tests at 3, 6, 12, 18, and 24 months. Though our cohort consisted of subjects at all ages showing a varied severity of initial illness, fewer females and young subjects were seen. Initially all had eye problems, but dominant symptoms were exertional dyspnea, cough, chest pain, sputum, and muscle weakness. A large number showed persistent depression mixed with anxiety, with disturbances of personality parameters. The early radiographic changes were lung edema, overinflation, enlarged heart, pleural scars, and consolidation. The persistent changes seen were interstitial deposits. Lung functions showed mainly restrictive changes with small airway obstruction; there was impairment of oxygen exchange. Oxygen exchange improved at 3-6 months, and spirometry improved at 12 months, only to decline later. The expiratory flow rates pertaining to large and medium airway function improved, but those for small airways remained low. There were changes of alveolitis in bronchoalveolar lavage fluid on fiber optic bronchoscopy, and in 11 cases positive MIC-specific antibodies to IgM, IgG, and IgE were demonstrated. On follow up, only 48% of the subjects were clinically stable, while 50% showed fluctuations. Thirty-two percent of the subjects had lung function fluctuations. Detailed sequential behavior over 2-4 years was predicted for dyspnea, forced vital capacity, maximum expiratory flow rate (0.25-0.75), peak expiratory flow rate, VO2, and depression score. A model for clinical behavior explained a total variance of 52.4% by using the factors of cough, PCO2 and X-ray zones in addition to above five parameters. The behavior of the railway colony group (1640 patients) revealed a similar pattern of illness. When this observed pattern of changes was transferred to the affected Bhopal city sections (with an equitable age-sex distribution), our model results were again validated. Thus the picture of MIC-induced disease seems similar despite the differences for age-sex and initial severity of illness in our cohort and in the population of Bhopal city as predicted by our model.

A simple and general entry to Aplysinopsine- type alkaloids by tandem Aza-Wittig/heterocumulene-mediated annelation.

Aza/Wittig-type reactions of iminophosphorane 8, derived from ethyl α-azido-β-(3-indolyl)propenoate and triphenylphosphine. with methyl isocyanate, carbon dioxide or carbon disulfide lead to the corresponding heterocumulenes 9, 10, and 11 which undergo cyclization by the action of nitrogenous reagents to give Aplysinopsine derivatives.

Mutagenicity of N, N'-dimethylurea and methylamine hydrochloride in the Ames Salmonella/microsome test: Absence of mutagenic response

Methyl isocyanate (MIC) in aqueous solution forms methylamine (MA) and N, N'-dimethylurea (DMU). MA in buffered system further converts into its salt form, methylamine hydrochloride (MAH). Therefore, MAH and DMU were evaluated for their mutagenic activity in the in vitro Ames Salmonella/ microsome mutagenicity test. The liquid preincubation protocol was followed, using tester strains TA98, TA100 and TA104 of Salmonella typhimurium, in the presence of 0, 5, 15 and 30% Aroclor 1254-induced rat liver S9 mixture. DMU and MAH did not induce a mutagenic response in any of the tester strains, both in the presence and in the absence of S9 mixture. The results therefore confirm that MIC in its native form or as its unknown metabolites is responsible for the mutagenic activity reported earlier by us in the his − tester strains TA100 and TA104 of Salmonella typhimurium (Mutation Res., 204 (1988) 123–129) and not due to its hydrolysis products, MA or DMU.

Acute toxicity of methyl isocyanate in rabbit: in vitro and in vivo effects on rabbit erythrocyte membrane.

Methyl isocyanate (MIC) interaction with the rabbit erythrocyte membrane increased the fluidity of the membrane and decreased the osmotic fragility of erythrocytes both in vitro and in vivo in rabbits intoxicated with MIC subcutaneously. MIC inhibited both acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) activities of erythrocytes dose-dependently in vitro, while in vivo a decreased trend in ATPase activity with unaltered AChE activity was observed. MIC also caused significant decrease in plasma sodium level with corresponding increase in potassium level in rabbits. The observed effects are due to MIC, per se, as the hydrolysis products of MIC, methylamine and N,N'-dimethylurea did not affect the erythrocyte fluidity and enzymes activities both in vitro and in vivo while they increased the osmotic fragility of erythrocytes in vivo in rabbits administered subcutaneously in equimolar concentration to MIC dosage. Inhibition of Na(+)-K(+)-dependent ATPase with altered permeability to cations and also probably water transport of plasma membrane due to MIC interaction are envisaged.

Does methyl isocyanate interaction with normal hemoglobin alter its structure and function?

The predominant biological effect of methyl isocyanate (MIC) intoxication in mammals is severe tissue hypoxia leading to acute lactic acidosis. In rabbits administered MIC subcutaneously (s.c.) the hypoxia was shown to be of the stagnant type resulting from hypovolemic hypotension. The occurrence of carbamylation of Hb by MIC in vivo was demonstrated unequivocally. Furthermore, the characteristic observation, dark red colored (cherry red) blood in animals exposed to MIC remained unexplained. This prompted the authors to investigate whether MIC exposure caused an alteration in structure and/or function of normal Hb leading to tissue hypoxia and the change in the color of the blood.

Pregnancy complications in Bhopal women exposed to methyl isocyanate vapor

Abstract This study was done to determine the effects of the methyl isocyanate (MIC) spill from the Union Carbide pesticide plant at Bhopal on December 3, 1984 on the course of pregnancy. For this purpose, 2622 households within a radius of 1 km from the plant were surveyed in August 1986, and the health status of 200 children prenatally exposed to MIC was surveyed again in July 1990. A total of 638 women in 2622 households stated that they were pregnant at the time of the accident; 315 (49.4%) of these pregnancies did not culminate in live births. Pregnancy loss was higher in women who were in their first (58.8%) than in those who were in their second (42.1%) or third (40.1%) trimester of pregnancy during the MIC spill. Out of 323 live births, 12.1% (n=39) died between 1 and 30 days after birth and an additional 8 died between 1 and 18 months of age; the 1–30‐day mortality rate was significantly greater than that recorded for the two years preceding the accident (27% in 1984 and 3% in 1983). Of the 273 s...

Modulation of microsomal membrane associated detoxication enzymes activity by methyl isocyanate (MIC) exposure

In the industrial disaster at Bhopal, India in 1984 the leakage of 40 tons of methyl isocyanate (MIC) gas from a pesticide plant claimed over 2,500 lives and left an estimated population of 15,000 people suffering from a variety of ailments. MIC induced changes in respiratory functions including bronchial asthma, pulmonary oedema, necrosis of alveoli, hypersensitivity, pneumonities and incapacitated pulmonary functions. Reports have also indicated changes in the respiratory tract of animals as a result of exposure to MIC, the lung being the main target organ attacked by MIC. The authors earlier report of the high dose single exposure toxicity to methyl isocyanate leads to alterations in biotransformation enzymes and their isoenzymic pattern. Recently, a drastic decrease in Na{sup +}, K{sup +}, and Mg{sup ++} ATPase enzyme levels by repeated MIC exposure has been shown. The present study further explores the biochemical basis of MIC intoxication with reference to consecutive dose dependent toxicity in terms of alteration in phase 1 and phase 2 membrane bound detoxication enzymes.

Objective thoracic CT scan findings in a bhopal gas disaster victim

The sudden spraying of stale methyl isocyanate (MIC), kept at ambient temperature in Tank No. 610 of the Union Carbide of India Limited, Bhopal, around midnight of 2/3 December 1984, has stimulated research and generated useful data in experimental animals regarding the nature of cold methyl isocyanate (1). However, the effects of the products of MIC on human subjects are not completely understood, even though some studies have reported multisystem involvement due to taxi; gases (2). One of the organs irreparably damaged is the lungs and the longterm impact of this damage is now under study. Since Computed Tomographic (CT) scanning of the chest has been utilized to quantify the damages in various lung disorders (3,4), two of the authors (S.S. and H.C.) suggested to the Madhya Pradesh Government that a study of CT scanning in toxic gas victims be conducted; projects were sanctioned by the Madhya Pradesh Government and Indian Council of Medical Research (ICMR). We, therefore report for the first time the CT scan findings in a toxic gas exposed subject of Bhopal.

BHOPAL DISASTER: Carbide now open to criminal charges

Union Carbide is apparently headed to criminal court in India—and possibly severe penalties for the company and some former executives, if found guilty—as a result of its December 1984 methyl isocyanate disaster in Bhopal that killed at least 4000 people. India's Supreme Court last week completed review of the controversial February 1989 settlement it decreed between Carbide and the Indian government, which ordered Carbide to pay $470 million in compensation to the victims. In the same decision, the court quashed all pending and future criminal and civil charges against Carbide and its Indian affiliate, Union Carbide India Ltd. Now the court has upheld the $470 million settlement, but allowed reopening of criminal charges. The 1989 settlement triggered protests by victims' groups throughout the country, leading the court to open the case to appeals. As it turned out the Indian government renounced the settlement in May 1990 and joined the petitioners in asking the court to ...

GC-MS Identification of MIC Trimer: A Constituent of Tank Residue in Preserved Autopsy Blood of Bhopal Gas Victims

Based on the external and internal findings of Bhopal gas disaster victims, it was apparent that the gases and particulate matter came out as an aerosol. This was possibly the pyrolysed, reformulated, reconjugated suspension of constituents of the tank E-610 of Union Carbide India Limited, Bhopal, while it was claimed to be methyl isocyanate (MIC) only. It was postulated by the manufacturer of MIC, that the material inhaled by the victims of the Bhopal gas disaster does not cross the lung barrier (UCC press conference on 14th December 1984). It was observed that the more the victims ran, the more aerosol they inhaled and the fatalities were observed in such victims. The tissues, which were preserved in the deep freeze, were randomly selected and analysed by GC coupled with MS (ITD) Finnigan MAT, UK. 14 out of 34 autopsy cases showed MIC trimer peak in extracts of blood. This was one of the constituents of the aerosol and was also located in the tank residue, thereby proving that the trimer had passed the lung barrier.

GC-NPD and GC-MS Analysis of Preserved Tissue of Bhopal Gas Disaster: Evidence of Methyl Carbamylation in Post-Mortem Blood

Twenty-five preserved autopsy blood samples of Bhopal toxic gas exposed victims were analysed by gas chromatography (GC) coupled with either Nitrogen-Phosphorous detector (NPD) or mass spectrometer (MS) for the presence of methyl carbamyl valine in terms of valine methyl hydantoin (VMH). 84% of these samples showed a positive test for VMH on GC-NPD and the identity of the peaks were further confirmed on GC-MS. The concentration of VMH in the gas-affected positive blood samples ranged from 2.56 to 51.28 nanomoles. These results indicate entry of methyl isocyanate (MIC), one of the constituents of the toxic cloud caused by the disaster, into the blood stream of victims who had inhaled gas.

Fetal loss and contraceptive acceptance among the Bhopal gas victims

The rates of fetal loss and family planning acceptance among Bhopal gas victims from 1984 to 1989 were compared to those of a control group. In all, 136 eligible women in the affected area and 139 women in the control area were interviewed. Care was taken to ensure that these women had conceived at least once during the previous five years. The The fetal loss rate among the gas-affected women was abnormally high (26.3 per cent) compared to that of women in the control area (7.8 per cent). Family planning acceptance in both areas was similar, with most women using permanent methods. In the case of temporary methods, the percentage of use was higher in the gas-affected area.

Carbamoylation of peptides and proteins in vitro by S-(N-methylcarbamoyl)glutathione and S-(N-methylcarbamoyl)cysteine, two electrophilic S-linked conjugates of methyl isocyanate

The reactivity toward peptides and proteins of S-(N-methylcarbamoyl)glutathione (SMG), the glutathione conjugate of methyl isocyanate, and the corresponding cysteine adduct, S-(N-methylcarbamoyl)cysteine (SMC), was investigated with the aid of in vitro model systems. Incubation of SMC or a trideuteriomethyl analogue of SMC with either the reduced or oxidized forms of oxytocin afforded similar mixtures of mono-, bis- and tris-N-methylcarbamoylated peptides. Structure elucidation of the mono and bis adducts by fast atom bombardment tandem mass spectrometry indicated that carbamoylation of oxytocin occurred preferentially at Cys-6 and that Cys-1 and/or Tyr-2 were secondary sites of modification. Upon incubation of S-[N-([14C]methyl)carbamoyl]glutathione (14C-SMG) with native bovine serum albumin (BSA), radioactivity became bound covalently to the protein in a time- and concentration-dependent fashion. "Blocking" of the lone Cys-34 thiol group of BSA in the form of a disulfide prior to exposure of the protein to 14C-SMG failed to decrease significantly the extent or time course of this covalent binding. It is concluded that carbamate thioester conjugates of MIC are reactive, carbamoylating entities which can donate the elements of MIC to nucleophilic functionalities on peptides and proteins. Free thiols appear to be preferred sites for such carbamoylation processes, a phenomenon that may have important toxicological consequences in the pathology of tissue lesions induced by MIC and related isocyanates.

Inhalation toxicity of methyl isocyanate: Biochemical and cytological profile of bronchoalveolar lavage fluid in rats

Acute pulmonary injury in rats following a single inhalation exposure to methyl isocyanate (3.2 mg l-1) was reflected by alterations in the biochemical and cytological constituents of bronchoalveolar lavage fluid (BALF) over a period of 30 days. Total protein, sialic acid and lactic acid contents of BALF were increased followed by a gradual decline to normalcy between day 3 and day 30 post-exposure. The activity of lactic dehydrogenase also increased progressively with time. The cellularity of BALF was increased significantly and primarily comprised of polymorphonuclear neutrophils at 8 days. The adherence of macrophages was unchanged but their viability was lowered at 30 days post-exposure. The results indicate the significance of bronchoalveolar lavage analysis in monitoring pulmonary toxicity by methyl isocyanate, which is characterized by the hypoxic condition and reduced cellular defence. Some toxic manifestations are potentially reversible with time after cessation of exposure.

Indian Activists Press Bhopal Accident Issues in U.S. Visit

Union Carbide's 1984 methyl isocyanate (MIC) disaster at Bhopal, India, is at best merely a dim memory in the minds of most Americans. But in terms of human toll, Bhopal easily tops all the other excesses of the 1980s. More than 4000 persons have died as a result of the accidental MIC discharge from storage tank 610. And not counted in that figure are the thousands of aborted fetuses and perinatal deaths that occurred and still occur as a result. Discounting the Chernobyl meltdown injuries and fatalities, Bhopal has been called the worst industrial disaster in history. The physiology and biochemistry of the approximately 160,000 survivors remain damaged. Scarred lungs affect perhaps about half that number. Researchers are finding serious damage to the immune systems of those exposed. Gastrointestinal problems are common. The psychological damage is severe. Spontaneous abortion rates and other reproductive pathologies remain high. What is probably saddest and most ominous of all, ...

AN OVERVIEW OF PROCESS HAZARD EVALUATION TECHNIQUES

Since the 1985 release of methyl isocyanate in Bhopal, India, which killed thousands, the chemical industry has begun to use process hazard analysis techniques more widely to protect the public from catastrophic chemical releases. These techniques can provide a systematic method for evaluating a system design to ensure that it operates as intended, help identify process areas that may result in the release of a hazardous chemical, and help suggest modifications to improve process safety. Eight different techniques are discussed, with some simple examples of how they might be applied. These techniques include checklists, "what if" analysis, safety audits and reviews, preliminary hazard analysis (PHA), failure modes and effect analysis (FMEA), fault tree analysis (FTA), event tree analysis (ETA), and hazard and operability studies (HAZOP). The techniques vary in sophistication and scope, and no single one will always be the best. These techniques can also provide the industrial hygienist with the tools needed to protect both workers and the community from both major and small-scale chemical releases. A typical industrial hygiene evaluation of a facility would normally include air sampling. If the air sampling does detect a specific hazardous substance, the source will probably be a routine or continuous emission. However, air sampling will not be able to identify or predict the location of a nonroutine emission reliably. By incorporating these techniques with typical evaluations, however, industrial hygienists can proactively help reduce the hazards to the workers they serve.

Vibrational frequencies in the à 3E state of methylnitrene

New observations have enabled the identification of another excited state vibration in the à 3E –X̃ 3A2 ultraviolet absorption spectrum of matrix-isolated methylnitrene. Two progressions in the C–N stretching frequency ν3 were detected in both CH3N and CD3N, with average intervals of 710 and 695 cm−1, respectively. For each isotopomer, corresponding lines in the pair of progressions are offset by frequencies appropriate for a methyl vibration. This provides the first clear evidence for excitation of the CH3 symmetric deformation (umbrella mode) ν2 in the upper state of the transition, with vibrational frequencies of 1166 cm−1 for CH3N and 1044 cm−1 for CD3N. These observations confirm earlier speculation on the absorption spectrum of matrix-isolated CH3N, and correlate with unidentified lines in the gas phase emission spectrum. The use of a new precursor, methyl isocyanate, in the generation of this radical is also of interest.

Biotransformation of methyl isocyanate in the rat. Evidence for glutathione conjugation as a major pathway of metabolism and implications for isocyanate-mediated toxicities

S-(N-Methylcarbamoyl)-N-acetylcysteine (AMCC), a chemically labile mercapturic acid conjugate, was identified by liquid chromatography-mass spectrometry (LC-MS) in the urine of rats dosed intraperitoneally with methyl isocyanate (MIC; 45.2 mumol). The corresponding cysteine conjugate, however, was not detected in urine. Following methylation, urine extracts were analyzed by thermospray LC-MS and the AMCC methyl ester was quantified by means of a stable isotope dilution assay procedure which utilized S-(N-methylcarbamoyl)-N-[2H3]-acetylcysteine [( 2H3]AMCC) as internal standard. The results showed that the fraction of the injected dose of MIC which appeared in 24-h urine collections as AMCC was 24.8 +/- 1.9% (mean +/- SD, N = 4). Thus, conjugation of MIC with glutathione (GSH), followed by metabolism of the resulting adduct to AMCC, appears to represent a quantitatively important pathway of biotransformation of MIC in the rat. However, in view of the known carbamoylating properties and in vitro cytotoxicity of S-linked conjugates of MIC, it seems unlikely that the GSH pathway of metabolism fulfills a conventional detoxification role in the case of MIC. In contrast, it is proposed that carbamate thioester conjugates of MIC, which can revert spontaneously to free MIC under physiological conditions, may actually contribute to the multisystem adverse effects of this highly toxic isocyanate in vivo.

Developmental toxicity of methylamines in mice

Monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) are endogenous substances as well as metabolites of methyl isocyanate, the chemical involved in the 1984 accident at Bhopal, India. Although methylamines exert several toxic effects including inhibition of protein turnover and oocyte RNA synthesis, their reproductive toxicity has not been investigated. We therefore studied the possible developmental toxicity of these amines using pregnant CD-1 mice and mouse embryo culture as experimental models. Intraperitoneal injections (daily from d 1 to 17 of gestation) of TMA at 2.5 and 5 mmol/kg/d significantly (p less than .001) decreased fetal body weight but not the placental weight or maternal body weight gain; however, 5 of 11 mice treated with 5 mmol/kg TMA died. Similar treatment with DMA and MMA did not exert any obvious maternal or fetal effects. All three methylamines, when added to embryos in culture, caused dose-dependent decreases in size, DNA, RNA, and protein content as well as embryo survival; the order of toxicity was TMA greater than DMA greater than MMA. The ability of methylamines to adversely affect fetal development suggests that these amines, especially trimethylamine, may act as endogenous teratogens under certain conditions.

Long term pulmonary impairment following a single exposure to methyl isocyanate

Groups of guinea pigs were exposed for 3 hr to 6, 13, 19, 27, or 37 ppm of methyl isocyanate (MIC). Pulmonary performance was evaluated immediately postexposure and for a period of 1 year in the animals surviving 19 or 37 ppm of MIC. At 6 and 13 ppm deterioration of pulmonary performance was observed but complete recovery occurred within a few weeks. In those animals surviving 19 or 37 ppm some recovery occurred but a long lasting impairment of pulmonary performance was observed. One year after a single exposure to MIC these animals presented a condition best described as chronic obstructive lung disease. Using flow-volume measurements during air breathing and during CO 2 challenge, animals surviving at 19 or 37 ppm presented typical abnormalities associated with airflow limitation along the conducting airways. One year after exposure lung hyperinflation was also present. At this time the poor ventilatory response to CO 2 was due to mechanical limitation of lung expansion during inspiration and airflow limitation during expiration. The findings were similar to humans with severe obstructive lung disease. Microscopic examination substantiated the flow-volume measurements in that the main bronchi, small bronchi, and bronchioles were found to have an increase in dense fibrous tissue, while the alveolar level was characterized by destruction of alveolar walls and an increase in septal thickness. Thus a single exposure to MIC, if the concentration is high enough, is sufficient to induce permanent pulmonary toxicity.