Investigating genetic outcomes following 1984 Toxic Union Carbide Disaster in India- Epidemiological challenges.

INVESTIGATING GENETIC OUTCOMES FOLLOWING 1984 TOXIC UNION CARBIDE DISASTER IN INDIA- EPIDEMIOLOGICAL CHALLENGES.

- Rajan R Patil*

[Published in : International Journal of Occupational Medicine and Environmental Health 2010;23(4):1 – 2DOI 10.2478/v10001-010-0025-4]



Abstract

Indian Council for Medical Research [ICMR] has called for proposals to study long term effects of 3rd December 1984 Union Carbide Industrial Disaster at Bhopal, one of the worst industrial disaster in the world, releasing poisonous Methyl Iso-Cyanate [MIC] gas into the environment affecting neighborhood population. Proposals are invited to study long term effect, if any , of toxic gas exposure on exposed population namely : - Genetic disorders, Low birth weight, Growth and development disorders, Congenital malformation, Biological markers of MIC exposure. [1]. This paper questions the appropriateness of launching a community based epidemiological study to investigate the possibility of genetic effects with a very short term environmental exposure to a chemical in a gaseous form.

Key Words
MIC, Genetic effects, India, health effects, bhopal


Discussion


Even designing such a study is exceptionally fret with challenges, starting with exposure ascertainment. Who is an exposed case? In the present case, there is no alternative to testimonial of affected people two and half decades back? Secondly, 25yr down the line, population composition within 2km radius of disaster site is so drastically different due to in and out migration- defining the study population and the sampling frame, and hence the opportunity to assess dose response keeping distance from the industrial site as the yard stick is completely lost. Compensation issue is bound to make many un-exposed claiming to exposed. The government list of 'victims' prepared for legal purposes, is highly political in nature, hence authenticity is always a suspect.
Purely from Occupational health point of view and for want of biological plausibility reasoning- there is no documented evidence of a chemical (in gaseous state) causing genetic effect following single exposure (inhalation) for a short duration(a day or two).


Inhalation related exposure like pneumoconiosis group are either particulate/fibrous form. Gases are known to elicit only immediate reaction ranging from irritation in eyes to fatal poisoning all essentially acute effects.

Absence of any precedence of short term exposure for a day or two in gaseous form. I am stressing on brief only two days exposure since the hazardous gas is expected to be in the atmosphere for only few hours in high concentration immediately after industrial disaster and following day concentration of MIC in the air is bound to negligent or due to air current. There was no evidence of heavy fog on Dec 3-4 1984 to believe that fog or Smog could have trapped MIC leading continued high concentration exposure to surround population. Neither is the MIC or its effluents radio active to suspect that population were at continued risk of exposure months and year after it was released accidentally in environment.


Repeated Genetic studies of exposure to environmental pollution and have clearly demonstrated that its only the chronic chemical exposures can cause genetic damage. [2]Except for Radio-active class, generally chemicals especially those taking GI route through ingestion have been to seen to cause genetic especially on somatic cells even effecting second generations. Classic case being Diethyl stilbestorol and Vaginal cancer of daughter whose mothers consumed DES during their pregnancy. Profound effect like birth defect was seen among drugs like the one infamous Thalidomide disaster. Please note in all the above case studies the route was orally ingested chemicals-drugs.



Even for chronic exposure to chemicals- persistent organic pollutants after decades life time of exposures there has been no conclusive evidence of genetic effects. The case in point has been DDT which is one of the most widely studied chemical on human health on which human have lived through food chain since it first started to be manufactured in 1938 [3].

To look for genetic effects as out come of Bhopal gas disaster do not have rationale because for mutations occur hazardous agent has to work on germ cells, and only Mutations with large effects, such as chromosomal rearrangements, can lead to “birth defects” only then there is potential for its effect be passed to the offspring. Now, such profound effects can not be expected with acute exposure of duration of a day or two as in case of industrial disaster in Bhopal and hence can not be expected to leading to trans-generational effects.


Researchers since then have been trying to document adverse effects in long stretched cohort studies for humans with generation time of 20 years were first exposed to vast number of synthetically produced chemicals. By mid 60s these individuals began to bear children and began to produce first generation of human exposed hazardous chemicals in utero-the first generation born with chemicals in their tissue. About 1980 this generation reached reproductive age, and the search for adverse health comes in their offspring continues even after 80 years which is a very miniscule time period for any genetic effects. [3]


Moreover, Indian union carbide disaster case, absence of biological marker for MIC, makes it nearly impossible to unerroneously classify study population into exposed and unexposed group to study unfavorable outcomes


Bhopal MIC exposure issue, 25 years down the line, inherent with nearly irresolvable methodological issues, all of which have potential to negate both positive or negative association equinamiously, either way findings will questioned.

In the past human epidemiological studies to determine genetic outcome of exposure have questioned only the health of the exposed individuals. It is not surprising that many epidemiological studies have failed to elicit any associations to link adverse health effects to chemicals (Type II error).


My reason for calling genetics studies of Bhopal gas disaster unethicality stems from the fact that In research ethics the appropriateness study design and its methodology and its duration are among essential requirement that is expected be in commensurate with expected out comes. Bhopal genetic study lacking any biological justification, and search of effects in small time line of 25 years and ICMR constraints of research funding capping it on to the maximum of Rs 30 lakhs INR all put together do not lend itself to proper genetic study outcome.

Yes, Studies on search for a biological marker for MIC, adverse health outcomes like exploring the effects of MIC acting as endocrine disruptors and mimics, human sperm counts, adverse reproductive outcome like miscarriages etc, high SMR among exposed. Studies looking for current health problems among the victims should be desirable so that they additional new victims affected by the gas may be brought and medical care and cared for alleviating their suffering and if the need be compensated financially.




Conflict of interest : None





Reference:

1. Call for Research Proposals on the Long term effect(s) of MIC gas , if any, on the Bhopal Population either exposed or affected (in December 1984) website http://icmr.nic.in/ (downloaded on Oct 1st 2009)

2. John W. Bickhama, Shabeg Sandhub, Paul D. N. Hebertc, Lounes Chikhid and Raghbir Athwal. Effects of chemical contaminants on genetic diversity in natural populations: in Mutation Research/Reviews in Mutation Research
Volume 463, Issue 1, June 2000, Pages 33-51.


3. Theo Colborn. The Wildlife/Human Connection: Modernizing Risk Decisions Environmental Health Perspectives 102, Supplement 12, December 1994





Correspondence

Dr. Rajan R Patil
Asst Professor.
Division of Epidemiology
School of Public Health
SRM University
Potheri, Kattankulathur - 603203
Greater Chennai,
INDIA.

Cell: 9600110872
Email : rajanpatil@yahoo.com