Vol.:(0123456789) 1 3 Nucleus https://doi.org/10.1007/s13237-019-00300-4 REPORT Frequency of micronuclei in population of Bhopal exposed to methyl isocyanate in 1984 Bani Bandana Ganguly 1,2  · Shouvik Mandal 1,3  · Nitin N. Kadam 2 Received: 28 May 2019 / Accepted: 22 September 2019 © Archana Sharma Foundation of Calcutta 2019 Abstract 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 signifcant (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 signifcant between adult and childhood exposure to MIC gas. The diferences of MN-incidences in the three severely exposure-zones (S1, S2, and S7) were signifcantly 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. Keywords Methyl isocyanate (MIC) · Human peripheral lymphocytes · Micronucleus test · DNA-damage · Exposure assessment Introduction Leakage of methyl isocyanate (MIC) gas from the Union Carbide India Limited (UCIL), Bhopal in December 1984 instantly claimed > 2500 lives and destroyed the fora and fauna completely in the UCIL-adjoining area; and left a huge toll of subsequent mortality and morbidity as a long term sequel of exposure [19, 25]. The quantum of imme- diate death and the extent of aftermath-efect recognized MIC-toxicity for frst time in the scientifc world. The report on MIC-toxicity of Kimmerle and Eben [26] could neither tackle immediate medical management nor introduce any antidote for lowering the pain of MIC-exposure. The acci- dental exposure signifcantly damaged the respiratory and ophthalmic systems by blocking the air-way passage and burning of eyes, respectively. Autopsies revealed cherry red colour of lungs and other internal organs. Fear of con- genital anomalies led to medical termination of pregnancies irrespective of the gestational age of the expectant moth- ers [23, 25, 36]. The magnitude of the disaster immediately led to investigation of MIC-efect in diferent physiological * Bani Bandana Ganguly mgmgeneticlab@yahoo.com; bani.b.ganguly@mgmhospitalvashi.net 1 MGM Center for Genetic Research and Diagnosis, Vashi Sector 3, Navi Mumbai 400703, India 2 MGM Institute of Health Sciences, Navi Mumbai, India 3 MGM Dental College and Hospital, Navi Mumbai, India