The deadly methyl isocyanate (MIC) gas released by the Union Carbide pesticide plant in Bhopal 25 years ago affected even the unborn, researchers say.
The toxic gas altered the immune system of those who were still in their mothers' wombs when the disaster struck, according to a recent study by researchers at the Bhopal Memorial Hospital and Research Centre (BMHRC) in Bhopal.
"Our study shows, for the first time, that in-utero MIC exposure during the Bhopal gas tragedy has caused a persistent immune system hyper-responsiveness in affected individuals," said Pradyumna Kumar Mishra, a BMHRC researcher. The findings have been published in the journal Occupational and Environmental Medicine.
Whether this "immune hyper-responsiveness" has any clinical implications will be clear only after follow-up of the exposed individuals, he said.
The release of 30-40 tonnes of MIC spreading over approximately 75 sq km killed at least 3,500 and injured thousands more. According to Mishra, there are more than 500,000 registered survivors of the tragedy.
The survivors continue to experience higher incidence of health problems, including respiratory, neurological, psychiatric and ophthalmic symptoms, Mishra said.
To understand the long-term implications of MIC exposure, doctors at BMHRC have conducted chromosomal studies in cultured mammalian cells using MIC as an experimental agent. "The results of the study have provided evidence to hitherto unknown molecular mechanisms of immunotoxic consequences of MIC exposure at a genomic level," he said.
According to Mishra, MIC had played havoc with the reproductive health of women and their girl children.
Menstrual abnormalities, vaginal discharge and premature menopause have emerged as common problems. "Besides affecting the reproductive health of the women, these conditions are also leading to social problems in conservative communities," he said.
Mishra said that investigations conducted so far at BMHRC and other places have raised a new question: for how long the gas victims would continue to suffer from multi-system disorders and whether future generations would also be affected by these abnormalities.
"In-depth molecular studies of ocular, respiratory, reproductive, immunological, genetic and psychological health must be continued if we wish to understand the extent and severity of long-term effects associated with the disaster," Mishra said.
He pointed out that the importance of such experimental studies cannot be understated "since any alterations at genomic level can have long-term health consequences that may range from accelerated ageing, carcinogenesis, immuno-compromised states and, more importantly, vertical transmission of genetic aberrations."