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  IN THIS Article
 ::  Introduction
 ::  Material and methods
 ::  Result
 ::  Discussion
 ::  References

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Year : 1986  |  Volume : 32  |  Issue : 4  |  Page : 192-4

Sequential study of thiocyanate levels in Bhopal water following methyl isocyanate gas leakage.

How to cite this article:
Acharya V N, Naik S R, Potnis A V, Bhalerao R A. Sequential study of thiocyanate levels in Bhopal water following methyl isocyanate gas leakage. J Postgrad Med 1986;32:192

How to cite this URL:
Acharya V N, Naik S R, Potnis A V, Bhalerao R A. Sequential study of thiocyanate levels in Bhopal water following methyl isocyanate gas leakage. J Postgrad Med [serial online] 1986 [cited 2023 May 31];32:192. Available from:

  ::   Introduction Top

More than three months after the leakage of methyl isocyanate (MIC) gas at Bhopal, we observed that serum thiocyanate levels in Bhopal subjects were still elevated.[3] This could have been due to prior administration of sodium thiosulphate injections which were earlier given to many Bhopal residents by the medical teams operating research projects initiated by the Indian Council of Medical Research. The Council had earlier instituted thiosulphate therapy to patients with persistent symptoms due to MIC exposure on the assumption that thiosulphate ion will displace the cyanide ion from the cyanide-cytochrome combination and form the relatively less toxic thiocyanates,[4] which are easily excreted into the urine. A cyanide pool theory has been postulated whereby it was assumed that cyanide and cyanate ions existed in the human body exposed to MIC as an interchangeable pool.[2] We therefore took a careful history about thiosulphate administration from our survey population and found that most of our subjects had not received any thiosulphate therapy. Of a minority who had received such therapy, most had received less than three injections more than 3 weeks before the survey. Therefore, high serum thiocyanate levels in these subjects could not be easily explained. It is well known that on the day of MIC gas leakage, the excess influx of water inside the storage tank had triggered off a runaway reaction forcing 41 tons of MIC to leak out into the atmosphere at high temperatures and pressures. It was therefore expected that water of Bhopal was contaminated with MIC and its products. We therefore considered the possibility that their serum thiocyanate levels may be sustained because of continuous ingestion of thiocyanates from Bhopal environment.

  ::   Material and methods Top

We thus tested water of Bhopal from different sources and compared it with tap water in Bombay with regard to thiocyanate content using the method described by Bowler.[1] Multiple water samples were obtained from surface and subsoil levels of the upper and lower lakes, the main sources of water for the city of Bhopal, as well as from the open and tube wells, and the taps at different points in the city. The samples were thus obtained from areas close to the Union Carbide of India Limited (UCIL) factory as well as from those over 10 km away from the factory both in the direction of the wind (i.e. Bhopal airport) and against the wind (i.e. Indrapuri). Control samples were obtained from the taps in Bombay. Samples of water from both Bhopal and Bombay were obtained at the time of our population survey in the month of March 1985 and later in May and August 1985. Additional samples were obtained from Bombay taps in December 1985.

  ::   Result Top

[Fig. 1] and [Table - 1] show the water thiocynate levels from different sources at different times from Bombay and Bhopal. Bombay water shows little variation in thiocyanate between March, May, August and December collections. On the other hand, Bhopal water regardless of the source, showed similar thiocynate levels and these were significantly higher in March than those in Bombay water (p< 0.01, Wilcoxan rank sum test). Thereafter there was a distinctly decreasing trend for thiocynate levels of Bhopal water by May 1985 and a return to normal levels in August, 1985.

  ::   Discussion Top

The above evidence strongly suggests that Bhopal water thiocyanates could have been responsible for the elevated blood levels of Bhopal subjects observed as late as 100 days after the MIC leakage. It is, however, not clear if these serum thiocynnates were :responsible for -the, persistent symptoms of Bhopal subjects we studied. Devkumar and Mukherjee[2] have discussed the fate of MIC in our environment. Like inhuman body, in soil and water too, MIC gets converted into methylamine (methyl carbylamine isocyanatomethane). Methylamine is capable of yielding cyanide in response to action of bacterial enzymes in soil and water, and of cellular enzymes in the human body to produce a cyanide-thiocyanate pool.[5] It is therefore, reasonable of presume that normalising levels of water thiocyanate in Bhopal indicate the detoxification of its environment with passage of time. This might be an indirect evidence to predict an improvement for the affected people in future. Our own estimates are that of 1,07,249 Bhopal subjects who are disabled, over 60,000 have severe disability and the remaining have mild and possibly reversible disability.[3] The spontaneous detoxification in terms of decreasing water thiocyanate levels over the last 8 months may be of help in reversal of such mild disability.

  ::   References Top

1.Bowler, R. G.: The determination of thiocyanate in blood serum. Biochem. J., 38: 385-388,1944.  Back to cited text no. 1    
2.Devkumar, C. and Mukherjee, S. K.: Methyl isocyanate-Profile of a killer gas. Science Today, 10-11, 16 1985.  Back to cited text no. 2    
3.Hayes, W.: "Pesticides-Studies in Man." Williams and Wilkins Co., Baltimore and London, 1982, p. 125.  Back to cited text no. 3    
4.Naik, S. R., Acharya, V. N., Bhalerao, R. A., Kowli, S. S., Nazareth, H., Potnis, A. V., Mahashur, A. A., Shah, S. and Mehta, A.: General Medical survey of methyl isocyanate gas affected population of Bhopal 15 weeks following exposure. J. Postgrad. Med., 32: 175-184, 1986.  Back to cited text no. 4    
5.Sax, N. I.: "Dangerous Properties of Industrial Waste Material." 3rd Edition, New York, 1969, pp. 1096-1097  Back to cited text no. 5    

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Online since 12th February '04
2004 - Journal of Postgraduate Medicine
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