Summer warming

Heat-related deaths present a public health challenge. State, civil society must protect the most vulnerable

2023 WAS THE world’s warmest year on record and it has been 47 years since the Earth has had a colder-than-average year. According to the India Meteorological Department (IMD), 2023 was the second warmest year in India in 122 years — the warmest ever recorded was 2016. The IMD predicts that most of India is likely to experience both above-normal maximum and minimum temperatures in April, May, and June.

States or regions most prone to increased heatwaves include Gujarat, Maharashtra, North Karnataka, Rajasthan, Madhya Pradesh, North Chhattisgarh, Odisha, and Andhra Pradesh. A high of 45.2 degrees Celsius was reported from parts of Raichur district, Karnataka, on April 6, with seven people from different villages suffering mild heat strokes.

The nature of the rising threats from heatwaves can be gauged from an Envistats-imd analysis which noted that the total average number of heatwave days annually has been increasing each decade; from 90 in 1990-99 to 94 in 2000-09, and to 139 in 2010-2019. The total annual average heatwave days increased from 42 in 2020 to 190 in 2022. Mortality statistics on account of heatwaves are reported by several agencies and those often do not agree on the exact numbers. While the IMD reported 10,545 deaths between 2000 and 2020, the National Disaster Management Authority (NDMA) put it at 17,767 and the National Crime Records Bureau (NCRB) reported 20,615. The National Programme on Climate Change and Human Health (NPCCHH) has initiated a reporting platform for heat-related illnesses (HRIS).

For the record, the NDMA reported the number of deaths as only four in 2020. Envistats-india reported 27 deaths in 2020 and none in 2021. However, in response to an unstarred question in the Lok Sabha, the Minister of Earth Sciences reported 1,274 heat-related deaths in 2019 followed by 530 in 2020 and 374 in 2021.

Notwithstanding these differences, there is apparent unanimity on three aspects. One, the actual number of deaths is likely to be higher than those reported; two, deaths peaked around 2015-16 and, three, they have been on the decline since. These trends are to be seen in the backdrop of two more statistics: the number of heatwave-affected states increased from nine in 2015 to 23 in 2019 and the number of average heatwave days recorded in this period increased nearly fivefold, from 7.4 to 32.2. This underscores heat as a growing public health challenge.

The cases of Ballia and Deoria districts in Uttar Pradesh are worth recounting. These district hospitals witnessed sharp spikes in admissions from certain areas and recorded 150 deaths in five days during the week of June 15-22, 2023. These were not medically certified as heat-related deaths but district officials confirmed that most were aged above 60 years and suffered from co-morbidities that “may have aggravated due to the heatwave”. The state-level investigation concluded that heatstroke could have been “contributory” to the deaths but not “causative”. Environmental analysts noted that temperatures at that time were about 45 degrees Celsius, with a relative humidity of 30-50 per cent — that meant, it would “feel like” more than 60 degrees Celsius. This is unquestionably life-threatening.

What is often lost in these statistics is a key question: What constitutes heat-related mortality given that exposure to heat is a significant threat to high-risk populations and contributes to increased morbidity and mortality? In theory, almost all heat-related deaths and illnesses are preventable while in practice, gauging the public health impact of extreme heat is difficult as HRIS are not yet mandatory to report to public health authorities in most countries. Environmental health experts draw attention to the fact that nonbiomedical external factors are often missed on death certificates leading to inaccuracies in cause-of-death reporting or estimations. The classic example is lightning strikes where the direct cause may be a falling tree branch or a fire but the indirect cause — the lightning strike — that triggered a cascade of events culminating in mortality does not find mention. The US National Association of Medical Examiners defines “heat-related death” as a death in which “exposure to high ambient temperature either caused the death or significantly contributed to it”.

Analyses from Europe are instructive. A standard method to estimate deaths occurring on account of these situations is recording and mapping excess deaths during the specified period. It is now agreed that over 70,000 excess deaths occurred across 16 countries with a combined population of about 400 million in Europe during the exceptionally hot summer of 2003. An epidemiological analysis of the Eurostat mortality database published in July 2023 quantified heat-related mortality burden during the summer of 2022, the hottest season in Europe so far. The number of heat-related deaths estimated for 35 countries between May 30 and September 4 is 61,672. These countries have a combined population of 543 million, a little less than half of India’s. Among them, those around the Mediterranean Sea experienced the highest mortalities — Italy, Greece, Spain, and Portugal. Despite the experience of 2003 and with most countries institutionalising adaptation measures, the magnitude of heatrelated deaths underscores the enormity of the challenge.

The Union Health Minister reviewed public health preparedness for the management of HRIS on April 3. Updated Heat Action Plans are available in 23 states and about 100 districts have initiated awareness campaigns. Those at the greatest risk include children, pregnant women and the elderly; those with pre-existing conditions such as diabetes and heart disease; those who are socially isolated and the poor. As the summer season intensifies, the state and civil society will be tasked with watching out for the extra-vulnerable.

The writer is professor (Community Health), Jawaharlal Nehru University, New Delhi and a collaborator in the Wellcome Trust Project, Economic and Health Impact Assessment of Heat Adaptation Action: Case studies from India

The cases of Ballia and Deoria districts in Uttar Pradesh are worth recounting. These district hospitals witnessed sharp spikes in admissions from certain areas and recorded 150 deaths in five days during the week of June 1522, 2023. These were not medically certified as heatrelated deaths but district officials confirmed that most were aged above 60 years and suffered from comorbidities that ‘may have been aggravated due to the heatwave’. The state-level investigation concluded that heatstroke could have been ‘contributory’ to the deaths but not ‘causative’.