The ICMR's first technical report on the health effects of the gas leak from the Union Carbide plant in Bhopal sees the light of day on the 20th anniversary of the colossal tragedy.in New Delhi
TWENTY years have passed since the world's worst chemical disaster struck the city of Bhopal on the night of December 2-3, 1984, killing about 2,500 people and maiming several thousands. Many more have died during this period from the chronic after-effects of the toxic methyl isocyanate (MIC) gas - and its reaction by-products - that leaked from a storage tank at Union Carbide India Ltd. (UCIL) pesticide plant in the heart of the city. The leak was the result of a run-away reaction caused by an uncontrolled increase in temperature and pressure.
It is indeed a great irony that the first technical report of the Indian Council of Medical Research (ICMR) on the `Health Effects of the Toxic Gas Leak from the Methyl Isocyanate Plant in Bhopal' should see the light of day only on the 20th anniversary of the colossal tragedy. The decade-long `Population Based Long Term Epidemiological Studies' carried out during 1985-1994 form the subject of this report. Epidemiological studies formed the core of the 20 main research projects on the various health-related aspects of the disaster that were initiated by the ICMR in January 1985. It had established a Bhopal Gas Disaster Research Centre (BGDRC) at the Gandhi Medical College in Bhopal to coordinate these activities. Many institutions and a number of scientists from all over the country participated in the research.
By not coming out in reasonable time with reports on the findings of the painstaking work carried out by the scientists (many of them have retired and some key people have since died), the ICMR has shown lack of respect for them and done disservice to the survivors. Perhaps the report would not have come out even now but for the dedication of a few retired scientists, with the ICMR having extended little additional infrastructure, manpower or financial support that such a large scale and vital study actually warranted. The reports on the environmental/industrial aspects of the disaster, produced by the Bhopal Commission led by the late C.R. Krishnamurthy under the Ministry of Environment and Forests, are still under wraps.
It is estimated that of the total population of Bhopal (in 1984-85) of over 8 lakhs, about 5 lakhs were exposed to the toxic gas(es). According to the report, nearly three-fourths of the deaths occurred within the first 72 hours of the leak. Though the number of deaths declined rapidly, the extent of the impact on the survivors' health was compounded by the fact that nothing was known about the toxic effects of MIC, the primary gas that escaped, and hence no one had a clue about a possible antidote to minimise the impact.
It was also apparent that a mixture of toxic gases, arising from the chemical reactions of MIC in the tank, would have escaped. But its exact nature too was unknown, making it difficult to assess what the victims would have inhaled, diagnose the morbidities that they presented accordingly and establish an appropriate line of clinical management. Surprisingly, even though UCIL was engaged in the manufacture of MIC since 1980, it had no information on its toxicity, its antidote or prevention against severe exposure to the gas. On the contrary, the parent company, Union Carbide Corporation (UCC), underplayed the toxicity of MIC and had even resorted to misinformation that led to a great deal of confusion and controversy even within the Indian medical community, particularly on the issue of `cyanide toxicity' and on the administration of sodium thiosulphate (NaTS), the known antidote to cyanide poisoning.
Within 72 hours of the tragedy, autopsies were undertaken at the Medico-Legal Institute in Bhopal under the late Heeresh Chandra, as autopsy was the only route to establish the cause of death and the nature of treatment to be adopted for the survivors. The most important finding of these initial autopsies, up to four weeks after exposure, was a characteristic "cherry red discolouration" of the lungs. Indeed, lung was the primary target organ, which showed a gross two to three times increase in weight over normal. The entire respiratory tract showed a series of pathological changes, including massive accumulation of fluid in the lungs (pulmonary oedema), enlarged air sacs and haemorrhages, generalised visceral congestion, cerebral oedema, and anoxic brain damage .
Most deaths had occurred owing to asphyxia arising from acute lung injury or acute respiratory distress syndrome (ARDS). In subsequent autopsies, from one to four months post-exposure, extensive pulmonary oedema and lesions with oozing fluid were seen. Later studies from four months to one year and beyond revealed the setting in of diffuse pulmonary fibrosis.
The exposed population displayed varying clinical features in the different post-exposure phases, classified as acute, sub-acute and chronic. Acute phase is (arbitrarily) defined as the first month after exposure. Most symptoms during this period were related to the effects of the gas on the eyes and the respiratory tract. Common eye complaints were foreign body sensation, intense irritation, burning, excessive lacrimation, photophobia and blurring of vision. Most of them had both conjunctival and circumcorneal congestion with relatively little oedema. There were also corneal ulcers. Prompt treatment, according to the report, seemed to clear the ocular symptoms.
Symptoms related to the respiratory tract included choking, sudden onset of breathlessness, chest pain, and severe dry or wet cough. Chest X-rays revealed diffuse infiltration of fluid into the lungs. A rather unusual symptom, says the report, was the victims' feeling of intense heat in the body even during the mid-December cold of Bhopal. In addition, there were complaints of muscle weakness, listlessness, sleepiness, loss of appetite, nausea, vomiting and fever. A small study on blood samples in this phase also revealed cases of increased white blood cells, higher eosinophilia count and higher than normal haemoglobin (Hb) levels.
In the sub-acute phase (one to three months post-exposure), persistent morbidities, suggesting multi-organ involvement, were predominantly seen. Even two months after the exposure, says the report, nearly 40 per cent of persons attending hospitals complained of breathlessness, chest pain, cough and fever. A characteristic feature among these patients was persistent rapid breathing (tachypnoea). The most important finding was that in a significant number of patients, the symptoms were disproportionate to the physical and radiological signs. That is, there appeared to be no correlation between the severity of breathlessness and impairment of lung function.
A significant number also presented gastrointestinal symptoms such as loss of appetite, nausea, vomiting and burning sensation in the middle-upper stomach region. A follow-up of patients who had predominantly ocular symptoms during the acute phase showed that the effect of the gas was only in the anterior eye chamber and in most cases the lesions had healed with no progressive deterioration of vision. The posterior chamber remained unaffected. However, a proportion of patients could end up with corneal opacities requiring surgical replacement of damaged corneal tissue, observes the report.
THE psychological consequences of the trauma were found to be fairly significant. About 10-12 per cent of the exposed population showed psychological manifestations. While symptoms of anxiety and depression were the foremost, there were also cases of disturbed sleep, `gas phobia' and feeling of hopelessness, with many families unable to cope with the extremely stressful situation. Psychological problems were particularly evident in bereaved, widowed and orphaned individuals.
Longer than three months post-exposure has been termed as the chronic phase. The report notes that, irrespective of the severity of exposure, a vast majority of the exposed subjects displayed even after three to four months after the disaster symptoms of cough (with or without expectoration), wheezing, chest pain, breathlessness, severe muscle weakness, body aches, abdominal pain, loss of appetite, visual disturbances, disturbed sleep and severe loss of capacity to work. Even though several victims showed improvement clinically, cough, chest pain, laboured breathing (dyspnoea) and weakness persisted in them.
But more significantly, many developed during this period for the first time respiratory symptoms of wheezing. A significant number of subjects displayed abnormalities in lung function tests (LFTs). In this phase too, the severity of pulmonary symptoms did not apparently correlate with chest X-rays, LFTs and physical examination. Psychological problems were seen in the chronic phase as well. In a randomised study of outpatients at 10 government clinics three to five months after the disaster, 22.6 per cent were found to be suffering from mental disorders. A similar number suffered from neurotic depression, anxiety and adjustment problems.
Since the morbidities seen were multi-systemic in nature, the need for a careful clinical surveillance programme on a continuing basis over a long term - at least over a decade - to answer many vital questions on the health effects of the exposed population, including understanding the toxicity of MIC itself, became imperative. What would be the course of their ailments and disabilities? How long will the effects last? Will they suffer from progressive systemic disorders? Will they suffer from brain damage or severe mental, neurological and psychiatric disorders? Will there be an increased incidence of cancers? When the victims have children, what kind of genetic defects and teratogenic effects can arise?
IT is to generate precise data on these questions that the ICMR designed and initiated the diverse set of multi-institutional projects. The particular one on epidemiological studies, which has resulted in the just released report, was undertaken from January 1985 through May 1994. The objective of the study was to determine health effects - both short-term and long-term - of the exposed population. The escape of a large quantity - over 40 tonnes - of MIC (and other toxic gases) theoretically implied that the entire population of Bhopal was exposed to their effects.
For the purpose of the study, the known symptomatology of (ocular and respiratory) effects of MIC was used to divide the population (of 832,904 in 56 municipal wards) into `exposed-affected' and `exposed-unaffected' groups. The latter served as the `control group' for statistical comparison. On the basis of the average death rates in the exposed/affected areas immediately after the accident, these were categorised as `severe' (death rate of 22 per 1,000 population), `moderate' (1.33/1,000) and `mild' (0.20/1,000). In percentage terms, of the total population, 3.9 per cent were affected severely, 8.6 per cent moderately and 50.1 per cent mildly, while 37.4 per cent were unaffected.
According to the report, most people included in the study had no fixed occupation nor any fixed source of income. Nearly 70 per cent of the people in the severely affected and control areas lived in kuccha houses, while housing in `moderate' and `mild' areas was relatively better. Prevalence of smoking habits ranged from 0.2 per cent to 14.3 per cent. The report notes that though the survey tried to minimise recording of false health status, given its linkage to the issue of monetary compensation, it could not be completely eliminated. These are important factors, points out the report, in analysing mortality and morbidity data. "Apart from the mortality, continuing respiratory morbidity is the most important finding of the studies. It will be difficult to analyse how much of it was due to the toxic gas(es) per se and how much due to the factors stated above," it adds.
Three-fourths of the deaths occurred in the first four days after which the rate rapidly dropped and there was no subsequent peaking. Also, the post-exposure chest X-rays showed resolution of the lung lesions with clearance of fibrosis, following the acute lung injury. This is suggestive of self-limiting disease process, notes the report. But, the report emphasises, it does not rule out persistent symptoms as a result of the residual scar lesions or their sequelae of recurrent infections, enlargement of air sacs leading to breathing problems and airway hyper-reactivity. This indeed remains the basic cause of chronic morbidity and ailments among the survivors even after 20 years.
"Initially," says the report, "it was difficult to assign the cause of death and the percentage of `causes unknown' was very high in all the areas." In 1986, the deaths due to respiratory causes were high in both `severe' and `moderate' areas whereas in the `mild' area, digestive and respiratory causes were the major ones. In 1992, deaths due to respiratory causes were the highest in all the three exposed areas. Also, in the `mild' area, nearly 20 per cent of the deaths were due to neurological or circulatory disorders. In 1993, the overall death rates among males in the `mild' area were high. This, according to the report, was partly due to very high death rates among the elderly in the 60-70 age group and above.
Lung- and eye-related morbidities were seen in more than 95 per cent of the population in all the three exposed areas. About three-fourths experienced disorders of the gastrointestinal tract (GIT) as well. This came down to 12 per cent in males and 17 per cent in females in the `severe' area after one year. The `severe' area had consistently higher rates for all periods and lung-related morbidity among males was higher in this area than in others.
The morbidity rates in all areas indicated three distinct trends, according to the report. In the `severe' area, the rates were low up to the surveys during May-November 1988. Later there was an increasing trend seen up to the survey in November-May 1991, and afterwards a decrease. The increase was observed in the `moderate' and `mild' areas too, but the peaks occurred in May-November 1990 and November 1989-May 1990 respectively. Interestingly, morbidity rate in the `mild' area was observed to be higher than in the `moderate' area during May-November 1991 and almost similar to that in the `severe' area from 1992 onwards. In females too, similar trend was seen except from November 1991-May 1992 onwards, the rates in the mild area were higher than in the `severe' and `moderate' areas. The control area too showed the same trend as moderate and mild areas but the rates were secularly lower.
In general, the morbidity studies showed that there has been multi-system involvement. The data collected is based on 40 symptoms, which showed that there was persistent high overall morbidity along with high respiratory, ophthalmic and GIT morbidity in the affected areas with the highest rates being in the severely affected area. Respiratory disorder has been the main cause of higher morbidity, though ocular morbidity had worsened after 1991.
The increase in the morbidity rate in the `mild' area in the 1990s shows that all the exposed areas - irrespective of the distance from ground zero - have been rendered vulnerable to long-term toxicity of the gases, the timing of the sequelae (including death) being dependent on the nature of the spread of gases in the atmosphere and the inhaled concentrations of the various gases by the victims. The higher mortality rates seen in `moderate' and `mild' areas as compared to `severe' areas during 1992-93 are also ascribed to the unknown pattern of spread of the toxic gas mix and inhaled amounts.
"Follow-up observations showed that mortality and morbidity rates have not declined close to the level of the control area even at the end of ten years," notes the report. Accordingly, epidemiological studies have continued beyond 1994. Probably it is still so even after 20 years. Indeed, according to the report, the long-term effects of this "one-time acute injury" to the respiratory tract and the ophthalmic system would continue to produce recurrent and episodic respiratory illness and possibly disability for a long time or even the whole life. People with pre-existing lung disease (about 5 per cent in any population) and smokers would have suffered more, says the report.
It is moot whether the mortality and morbidity could have been significantly reduced if MIC toxicity was better understood during the acute phase. In this context, the issues of possible cyanide toxicity and the sodium thiosulphate antidote therapy, that became highly controversial, assume significance .
Even though the ICMR report has become public only now, the findings of the study have been known to the agencies concerned. However, these do not appear to have been gainfully and systematically used for clinical management of the victims. "Bhopal population today is more vulnerable; pulmonary fibrosis has accentuated, there is occlusion of bronchioles," points out S. Siramachari, an ICMR emeritus scientist and the editor of the present report. "The monitoring of these 80,000-odd people should be an ongoing process and the State health authorities should use their data as a base. Even now some concrete steps can be taken. Mobile units can be easily deployed with blood gas apparatus, lung function tests and oxygen concentrators. These should make regular visits to the victims and offer therapeutic support for their predominantly chronic respiratory illnesses," recommends Sriramachari.