The Bhopal gas explosion in 1984-;one of India's worst industrial disasters-;may have heightened the risk of disability and cancer in later life among future generations, curbed their educational attainment, and prompted a fall in the proportion of male births the following year, suggests research in the open access journal BMJ Open.
The disaster is likely to have affected people across a substantially more extensive area than previous evidence suggested, say the researchers.
During the incident, toxic methyl isocyanate gas leaked from a pesticide plant near the city of Bhopal, spreading up to 7 km and exposing more than half a million people to the gas, killing 30,000 people. But research suggests that even those not directly exposed to the gas were affected.
Health consequences among the hundreds of thousands of survivors were wide ranging. But it's not clear if the effects extended across generations, so a team of US researchers looked at the potential impact on children born to women survivors of Bhopal.
They drew on health and education data from the fourth wave of India's National Family Health Survey (47,817 people born between 1960 and 1990 and living in Madhya Pradesh in 2015) and the 1999 Indian Socio-Economic Survey (13,369 people living in Madhya Pradesh) to estimate the health effects of the gas leak among 15-49 year olds living in Madhya Pradesh in 2015-16 as well as their children (1260) born between 1981 and 1985.
Analysis of the data showed there were long term, intergenerational effects. Men who were in the womb at the time and whose mothers lived close to Bhopal-;within 100 km-;were more likely (1 percentage point-;over twice the baseline rate of 0.04%) to have a disability that affected their employment 15 years later.
More than 30 years later, men who had never moved also had a 27-fold higher risk of cancer and 2 fewer years of education than adults born before or after the disaster and who lived further away.
The sex ratio of births in 1985 also changed among children born up to 100 km away from the incident, suggesting that the effects of the disaster may have been more widespread than previously thought.
Among women living within 100 km of Bhopal the proportion of male births fell from 64% between 1981 and 1984 to 60% in 1985. But there was no difference in the sex ratio among women who lived more than 100 km away during the same period.
This finding is consistent with male fetuses being more affected by external stressors, say the researchers.
They acknowledge certain limitations to their findings, including the inability to assess the exact range of exposures to the toxic gas or the potential impact of migration and deaths attributable to the explosion, all of which may have affected their estimates.
Nevertheless, they conclude: "These results indicate social costs stemming from the Bhopal gas disaster that extend far beyond the mortality and morbidity experienced in the immediate aftermath.
"Moreover, our results suggest that the Bhopal gas disaster affected people across a substantially more widespread area than has previously been demonstrated."
They add: "The evidence presented in this paper starkly highlights the long-term, inter-generational health and human capital effects of the Bhopal gas disaster, and underscores the need for ongoing survivor support, as well as robust regulatory protection."
McCord, G. C., et al. (2023) Long-term health and human capital effects of in utero exposure to an industrial disaster: a spatial difference-in-differences analysis of the Bhopal gas tragedy. BMJ Open. doi.org/10.1136/bmjopen-2022-066733.