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Researchers who found that a single day of extreme heat leads to approximately 3,400 excess deaths in India have analyzed how heatwaves affect mortality at the district level, hoping to bring to light “a profound and troubling environmental injustice.”

States least able to finance adaptation are “precisely those facing the greatest heat mortality risk,” write Piyush Narang and Ashok Gadgil of the India Energy and Climate Center, Goldman School of Public Policy at the University of California Berkeley, in a study published last month in the journal Frontiers in Environmental Health.

Narang and Gadgil designed their study to address information gaps about heat-related deaths in India. Their research assesses extreme heat impacts at a district level to show trends that have been missed in countrywide or city-specific analyses. They also measured “all-cause mortality” rather than relying on heatstroke or disaster statistics, which the researchers say “substantially underestimate” the true death toll from extreme heat.

Nationally, 3,400 excess deaths result from a single day of extreme heat, while a five-day heatwave causes nearly 30,000, the study estimates. In the northern state of Uttar Pradesh, it estimates 8,100 excess deaths during a five-day heatwave. Districts in other high-risk states, including Ahmedabad, Jaipur, and Surat, each exceeded 250 excess deaths during single events.

Narang and Gadgil then cross-referenced their mortality estimates with district-level economic output, finding that the five states bearing the highest heatwave mortality burden account for 66% of heat-related excess deaths but only 29% of India’s GDP. The divergence demonstrates that “heatwave mortality risk is not merely proportional to population size but is structurally concentrated in states with lower economic output, precisely those with the least fiscal capacity to invest in adaptation.”

The findings have important implications for India’s strategies to address rising extreme heat, showing that existing heat action plans—which are usually developed at the city level—do not address the concentration of heat mortality risk in states with low fiscal capacity.

People across India are already experiencing extreme heat. The New York Times reported that the country has faced multiple heatwaves since April, with temperatures reaching over 43°C in some areas. In rural areas of Uttar Pradesh, people are adjusting their work hours earlier to avoid the most intensely hot parts of the day, but limited resources mean that many are often forced to bear the impacts of extreme heat, reports BBC News.

Bloomberg columnist David Fickling writes that, while heatwave severity is often reflected by high daytime temperature peaks, a more dangerous indicator is sustained nighttime temperatures that never drop enough to bring respite. This trend is most noticeable in urban megacities that are projected to continue expanding—“felling trees, filling in wetlands, and paving soil” that would otherwise help moderate temperatures.