Climate change worsening heat stress and disease risks in India: Lancet report

Half of India's heatwave days in 2016-2025 were attributable to climate change, while rising heat exposure, infectious disease risks and air pollution are taking a growing toll on health, livelihoods and productivity

Climate change is increasingly affecting health in India, from exposure to dangerous heat and heat-related illnesses to rising risks of infectious diseases and deaths linked to air pollution. Half of the heatwave days experienced by people in India between 2016 and 2025 were directly attributable to climate change, while heat exposure caused an estimated 193 billion potential labour hours to be lost annually.

The 2026 Lancet Countdown on Health and Climate Change report warns that these impacts extend beyond extreme weather, affecting sleep, productivity and livelihoods, and calls for climate change to be recognised as a global health emergency. The report finds that changing environmental conditions are increasing the suitability for dengue, malaria and waterborne infections, while air pollution continues to cause substantial premature mortality. Its findings highlight the growing links between climate change, public health and India's economic well-being.

Global health risks are escalating

The 10th annual Lancet Countdown report, led by University College London (UCL) in collaboration with the World Health Organization (WHO), draws on the work of 146 researchers from more than 100 institutions across over 30 countries. It tracks 54 indicators of climate change's impact on health.

Globally, heat was linked to an estimated 540,800 deaths annually between 2016 and 2023, with 68% attributed to climate change. In 2023 alone, heat was associated with an estimated 710,000 deaths worldwide. Heat-related reductions in labour capacity cost the global economy an estimated US$1.07 trillion in potential income in 2025. While clean energy investment and health-system preparedness have improved, the report warns that progress remains insufficient.

"A decade after the Paris Agreement, our findings are unambiguous: the health harms of climate change are growing faster than the world's response to them, and in many cases even accelerating," Professor Marina Romanello, executive director of the Lancet Countdown at UCL, said. The India findings and takeaways are significant.

Heat threatens health, sleep and livelihoods

People in India experienced an average of 10.6 heatwave days annually during 2016-2025, of which 5.3 days, or 50%, were directly attributable to climate change.

The effects extend beyond heatwaves. People were exposed to more than 2,600 hours annually, on average, when heat posed a moderate or higher risk of heat stress during moderate outdoor activity, such as brisk walking. This was over 200 hours more than the annual average in the 1990s. High night-time temperatures also disrupted sleep: people lost an estimated 64 hours annually during 2021-2025, around three hours more per year than during 1986-2005.

According to Dr Puneet Mishra, the heatwave led to a surge in heatstroke, dehydration, dizziness, and cardiovascular complications among vulnerable populations. "Hospitals reported a severe increase in emergency visits for heat-related illnesses within a few weeks," he said.

The report does not provide a standalone estimate of total heat-related deaths in India. However, the monetised value of heat-related mortality among people aged over 65 averaged US$33.8 billion annually during 2021-2025, a 205% increase compared with 2000-2004. Heat exposure caused an average annual loss of 193 billion potential labour hours in India during 2016-2025, 75% higher than the annual average in the 1990s.

Dengue and malaria transmission risks are changing

The transmission potential of dengue spread by Aedes albopictus mosquitoes increased by 84% between 1951-1960 and 2016-2025, rising from below to above a transmission threshold of one. Transmission potential for Aedes aegypti remained high, averaging 2.4 during 2016-2025.

The number of months environmentally suitable for malaria transmission increased by approximately 19% for Plasmodium falciparum and 18% for P. vivax compared with 1981-1990, reaching an average of around four months annually. The findings underline the need for climate-informed disease surveillance and preparedness.

Coastal infection risks and warming waters

The length of India's coastline with environmental conditions suitable for Vibrio bacteria transmission increased by 27% compared with 1982-1991, reaching approximately 2,740 km in 2025. Estimated vibriosis infection cases nearly doubled between the two periods, reaching an annual average of approximately 97,500 during 2016-2025. Coastal sea surface temperatures around India were 0.4°C higher during 2023-2025 than the 1981-2010 average.

Wildfire smoke and air pollution cause substantial harm

Wildfire smoke was associated with an estimated 90,300 deaths annually in India during 2021-2025, compared with 67,800 annually during 2003-2012. Exposure to fine particulate matter, or PM2.5, was associated with more than 2.2 million deaths in India in 2023, a 22% increase from 2016. Fossil fuel combustion contributed to 38% of these deaths, with coal accounting for 67% of fossil-fuel-related air-pollution deaths. Household air pollution linked to polluting fuels was associated with approximately 617,000 deaths in 2023, down from 783,000 in 2016. The monetised value of premature mortality associated with air pollution reached approximately US$517 billion in 2023, equivalent to 13.5% of national GDP.

Experts call for stronger heat-health preparedness

Prof. T. P. Sabin, scientist at the Indian Institute of Tropical Meteorology, said prolonged exposure to high temperatures affects everyday activities, outdoor workers, productivity and overall well-being. The finding that half of India's heatwave days during 2016-2025 were attributable to climate change shows how human-induced warming amplifies exposure to hazardous heat, he said.

Experts say India's heat preparedness must move beyond forecasting extreme temperatures to anticipating their health consequences. Prof Sabin called for impact-based heat warnings, improved heat-health surveillance and timely communication with vulnerable communities. Coordination among meteorological services, health authorities and urban planners, alongside shaded public spaces and heat-resilient urban planning, will be crucial to reducing heat-related illness.

Hospitals must be equipped to manage surges in heatstroke, dehydration and cardiovascular complications. Impact-based warnings should reach vulnerable communities, particularly older people and outdoor workers. The report's findings point to the need for India to combine emissions reduction with stronger health systems, climate-informed disease surveillance, cleaner energy, improved water security and protection for communities most exposed to extreme heat and environmental challenges.