Tracking ‘heat health’ in summer of heat waves
India needs to adopt a decentralised model to deal with extreme events, drawing on the planning and communitisation models enshrined in the National Health Mission and leveraging community-derived knowledge
The political heat that the ongoing Lok Sabha polls have generated aside, the effect of the impending weeks of summer on the campaign and the actual polling process is part of the current discussion. Union minister Nitin Gadkari fainted during an election rally in Maharashtra’s Yavatmal district on April 24, but recovered soon. On Sunday, the India Meteorological Department (IMD) said a severe heat wave has swept over east and south peninsular India and will continue for the next five days, spiking temperatures in Gangetic West Bengal, Odisha and Bihar, parts of Jharkhand, pockets of Rayalaseema, interior Karnataka, and Telangana.
Recognising the importance of heat health, the single largest cause of weather-related deaths in the United States (US), the US National Weather Service (NWS) and the Centers for Disease Control and Prevention (CDC) introduced a new category of heat risk on April 22 (Earth Day) — Magenta. In the US, 1,200 recorded deaths were attributed to heat last year and 120,000 people were taken to the emergency room. The US has a new online heat-risk system that combines meteorological and medical risk factors with a seven-day forecast. The NWS HeatRisk is a colour-numericbased index that provides a risk forecast of heat-related impacts over a 24-hour period. It factors in three parameters: How unusual the heat is for the time of the year; the duration of the heat, including both daytime and nighttime temperatures; and whether those temperatures pose an elevated risk of heat-related impacts (based on data from the CDC). Magenta is the highest level and deadliest of the five heat threat categories, “rare and/ or long-duration extreme heat with little to no overnight relief.”
The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. At present, IMD and the National Disaster Management Authority (NDMA) jointly issue colour-coded impact-based heat warnings. The current classification issued on April 4 is as follows: Green (Heat Index less than 40 degrees Celsius), normal day; Yellow Alert (40-50 degrees Celsius), heat alert; Orange Alert (50-60 degrees Celsius), severe heat alert for the day; and Red Alert (higher than 60 degrees Celsius), that is extreme heat alert. The Indian classification was experimentally introduced in 2023, when Red signified higher than 55 degrees Celsius; all the categories have been reset in 2024 for correspondingly higher temperatures. The US Magenta begins at about 53 degrees Celsius and therefore, corresponds to the Indian Red.
The National Crime Records Bureau (NCRB) reported 20,615 heatrelated deaths between 2000 and 2020, though other databases report somewhat lower figures. Both national and state governments as well as major cities have formulated heat action plans to combat heat-related illnesses (HRIs) and reduce mortality and morbidity.
The National Programme on Climate Change and Human Health (NPCCHH) is working towards creating awareness among vulnerable communities, health care providers, and policymakers, strengthening the capacity of health care system and preparedness, and enabling partnerships and synergy to ensure that health is adequately represented in the climate crisis agenda.
HRIs are currently approached through an acute disaster management lens, from the standpoint of the precautionary principle. Framing it as a health emergency often places it in a response framework that is too immediate while overlooking more gradual effects and impacts. The concept of slow disaster has emerged from a more nuanced understanding of the Covid-19 response and may help build a climate-resilient health system that India needs. Magenta of the NWS-CDC classification characteristically deals with “long-duration heat” rather than a single day’s temperature, and that is a refinement India may need to consider.
Heat health is generally addressed through the meteorological or medical lens and receives little attention in terms of its social determinants. Granular analyses have revealed higher ambient temperatures among communities and neighbourhoods that have lower income and are under-resourced, including densely populated urban dwellings, and housing characteristics with a lack of access to air cooling or air conditioning. Individuals living in these disproportionately hotter settings are at higher risk, especially when it comes to vulnerable groups such as the elderly, infants and young children, pregnant women, those with chronic morbidities and outdoor workers.
There is an emerging consensus that while national, state or city plans provide overall guidance and lay down the foundations, the last mile challenges lie in identifying and locating communities at high risk for heat health hazards. There has been considerable progress in several countries on mapping heat vulnerability by including environmental and sociodemographic indicators with adverse health outcomes during extreme heat events. These need to be overlaid with vulnerability information obtained through health surveys, analysis of mortality data, chronic disease databases (if available) and records of ambulance calls. The need to map microclimatic zones has been advocated by Indian experts too.
The path ahead lies in shifting from the traditional top-down commandand-control disaster management model to a decentralised one, drawing upon bottom-up planning and communitisation models enshrined in the National Health Mission (NHM), and leveraging and strengthening community-derived knowledge about practices to limit mortality and morbidity during extreme heat events.
Rajib Dasgupta is professor (community health) at JNU and a collaborator in the Wellcome Trust Project: Economic and Health Impact Assessment of Heat Adaptation Action: Case studies from India. The views expressed are personal