Frequency of micronuclei in population of Bhopal exposed to methyl isocyanate in 1984


Micronuclei represent whole chromosome or large acentric fragments lagging behind the ana-telophasic separation of cell division. However, it progresses towards completion of karyokinesis and eventually gets included in one of the two daughter cells through cytokinesis. The frequency of micronuclei was estimated in 107 subjects exposed to methyl isocyanate (MIC) gas 30-years post-disaster and compared with 35 unexposed subjects of similar socio-cultural background from the same geographical region. Ethical approval and participants’ informed consent were obtained, and quality issues were validated prior to the proposed investigation. Peripheral blood was collected for each participant from their residence and transported to Mumbai for technical processing and cytogenetic analysis. Replicate cultures with 0.5 ml of whole blood were stimulated in 5 ml of serum supplemented RPMI1640 medium and maintained at 37°C for 72 h. The cells were dropped onto chilled slides following standard harvesting schedule, air dried and stained in Giemsa. Microscopic observation of 1000 cells for each subject has recognized lymphocyte cells (MNC) with micronucleus (MN). The ratio of MN and MNC indicated number of micronuclei per micronucleated cell. Statistical analysis revealed exposure related incidences of MN, MNC and MN/MNC, which was significant (p < 0.05) when compared with unexposed population and/or between moderate and severe exposure status (MN) of the population. Age-related MNC-incidence was significant between adult and childhood exposure to MIC gas. The differences of MN-incidences in the three severely exposure-zones (S1, S2, and S7) were significantly higher than the unexposed zones (C14, C16). The incidence of MN was consistent with our earlier study on chromosome aberrations detected in the same population 30-years post-disaster. However, the MN/CA incidences cannot be directly linked to MIC-exposure of 1984 owing to contribution of several confounding factors over 30 years. Nevertheless, the study could be considered as a low-cost tool but useful for estimation of DNA-damage in risk-assessment.

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The authors wish to acknowledge financial support (partial) of Indian Council of Medical Research (Grant Number: ICMR-65/BBG-1/NCD-II & NIREH/IMP/BBG/2013/01) and Mahatma Gandhi Mission Trust extended for this publication. The authors also acknowledge the administrative support of ICMR-National Institute for Research in Environmental Health, Bhopal, and technical support of Ms. Poonam Pawar.

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Ganguly, B.B., Mandal, S. & Kadam, N.N. Frequency of micronuclei in population of Bhopal exposed to methyl isocyanate in 1984. Nucleus 62, 269–275 (2019).

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  • Methyl isocyanate (MIC)
  • Human peripheral lymphocytes
  • Micronucleus test
  • DNA-damage
  • Exposure assessment