Thermal Injustice: 20,000 Indians Died in Heatwaves In 20 Years – Caste a Key Factor

New Delhi: Heatwaves killed nearly 20,000 people in India between 2001 and 2019, a recent study has found. The study found that men were more susceptible to deaths caused by heat waves in the country.

Another recent study also found that heatwave deaths are divided along caste lines – more people belonging to marginalised communities died in India from exposure to heat than people from other communities. This is a kind of “thermal injustice”, researchers who work on the study say. 

Reports by the United Nations’ Intergovernmental Panel for Climate Change (IPCC) such as this one in 2021 have warned that India, along with many other parts of Asia, will likely experience more extreme weather events – including heatwaves – in the years to come.

The heat is also breaking records every year. According to the India Meteorological Department, February 2025 was the hottest that India has witnessed in 125 years.

Killer heat

Heatwaves can adversely impact human health. And heat strokes – which can cause not only mild symptoms such as exhaustion and dizziness but also death – are common during this time.

A team of scientists from the O.P. Jindal Global University in Sonipat, Haryana, studied deaths caused by extreme outdoor temperatures in India, and also looked at age and gender parities in such deaths. For this, they analysed data from several governmental sources – such as temperature data from the India Meteorological Department and mortality data from the National Crime Records Bureau.

“These strong associations between caste, occupation, and heat stress exposure are best described as “thermal injustice”, the study noted.

The team found that between 2001 and 2019, India reported 19,693 deaths due to heatstroke and 15,197 deaths due to cold exposure. However, these numbers would be an underestimate due to the underreporting of deaths caused by exposure to such extreme temperatures, the study – published on April 29 in the peer-reviewed journal Temperature – noted.

People in the age-group of 45-60 years were most susceptible to die both due to heatstroke and cold exposure, followed by the elderly (60 and above) and those between 30-45 years. The study also found that deaths from heatstroke are more common among men; male deaths were three to five times higher due to heatstroke when compared to deaths of women during this time.

“The higher death toll from heatstroke in working-age men may reflect the fact that men are more likely to work outdoors than women,” Pradeep Guin, professor at the O.P. Jindal Global University and co-author of the study, said in a statement.

State-wise data from 2001 to 2014 also showed that the three states with the greatest number of deaths due to heatstroke were Andhra Pradesh, Uttar Pradesh and Punjab. 

Per their study, the findings show “an urgent need to strengthen welfare and social support systems and invest in built environment and livelihood interventions to counter the avoidable mortality from extreme temperature events”.

“With an intense heatwave forecast to hit most of the country this summer and extreme weather events becoming more frequent around the globe as the world warms, there is no time to be lost in raising awareness about the dangers of extreme temperatures and putting in place measures to reduce their impact. Support systems exist, but more needs to be done,” Guin, who studies climate change, the environment, health, politics and governance, commented in a press release.

“We believe that the government should consider offering some form of social support to outdoor workers, particularly low-income workers and those on a daily wage, who may feel they have no option but to turn up to work, whatever the temperature is,” commented Nandita Bhan, a co-author of the study and professor at the Jindal School of Public Health and Human Development at the O.P Jindal Global University, in a press release.

'Thermal injustice'

Deaths due to heatwaves in India are also divided along caste lines, according to another recent study. 

A team from institutes including the Indian Institutes of Management (in Bangalore and Ahmedabad) used satellite data to obtain fine-scale information on heat stress exposure during the summers of 2019 and 2022 and compared this with data from the Periodic Labor Force Survey, which contained several demographic indicators to specifically look at people (a sample size of more than 1 lakh) who worked outdoors.

They found that people from dominant castes spent 27-28% of their working time outdoors, whereas people belonging to the Scheduled Tribes (ST) communities spent 43-49% of their working hours doing such work. Together, people belonging to both the Scheduled Castes (SC) and ST communities spent more than 75% of their working hours outdoors in at least 65 districts across the country over the two years. But could this be because marginalised groups live in hotter areas? The team was able to ascertain that this was not the case by analysing exposure to land surface temperature at night.

“These strong associations between caste, occupation, and heat stress exposure are best described as “thermal injustice”, the study noted.

“While workers in a free market would be free to choose combinations of wages-occupational risks that optimise their preferences, our findings imply that the positions of these combinations are shifted by caste, to the detriment of marginalised groups in India,” the study said.

Further, the study’s “robust evidence for the association between caste identity and exposure to heat stress shows why adaptation and mitigation plans in India must account for the hierarchical social order characterised by the “division of labourers” along caste lines rather than the mere division of labour,” it added.

Data from the NCRB – which Guin and his co-authors used in their latest study – did not provide any caste-related information, so they could not test the issue of caste-specific deaths caused by heatwaves in their study, Guin told The Wire. 

“The Demography article is very interesting, and it is evident that scholars there have used data to test the association between caste and heat stress, and recommending implementation of caste-based adaptation and mitigation plans,” Guin told The Wire over email.

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