Just how vulnerable is a particular part of the country in case of a heat wave? A team of researchers drawn from several institutions including the Indian Institute of Public Health, Gandhinagar (IIPH-G), have created the first heat vulnerability map of India, locating the places that are likely to suffer the worst from a spell of high temperatures.
The heat wave vulnerability index (HVI) drawn up by the researchers puts 10 districts in the ‘Very High’ category — 4 of which are in Madhya Pradesh, 2 in Chhattisgarh, and 1 each in Jharkhand, Rajasthan, Odisha and Gujarat. 97 of the country’s districts are in the ‘High’ risk category, while the bulk of the remaining districts are in ‘High Normal’ (213) and ‘Low Normal’ (225) categories respectively.
75 districts are in the ‘Low’ HVI category; 10 in ‘Very Low’. Districts in the latter group are at least risk from a heat wave, and are located in Kerala, Goa and Lakshadweep.
The researchers proposed their heat vulnerability index in an article published on March 30 in the International Journal of Environmental Research and Public Health, a publication of the Basel-based Multidisciplinary Digital Publishing Institute (MDPI), an open access platform for peer-reviewed research. Despite several recent deadly heat waves in India, and the increasing recognition of heat as a public health problem, India did not thus far have an HVI.
“Our mapping showed that the districts with higher heat vulnerability are located in the central parts of the country,” Dr Dileep Mavalankar, director of IIPH-G and a co-author of the paper, told The Indian Express. The chief author is Gulrez Azhar, an Aligarh Muslim University alumnus and doctoral candidate at Pardee RAND Graduate School, Los Angeles, and the other co-authors are Shubhayu Saha of the Rollins School of Public Health at Emory University, Partha Ganguly of IIPH-G, and Jaime Madrigano of the RAND Corporation.
The researchers evaluated demographic, socio-economic and environmental vulnerability factors, and combined district level data from several sources, including Census 2011, health reports, District Level Household Survey 3, and satellite remote sensing data from the Indian Space Research Organisation to draw up the index.
Districts were selected as units for the analysis. Household amenities were assessed through the presence or absence of drinking water on the premises, a good house, a mobile phone, radio and TV. Population health was assessed through the immunisation status of children between age 12 and 23 months, and presence of a health facility within 3 kilometres.
“Mapping showed that the districts with higher heat vulnerability are located in the central parts of the country. On examination, these are less urbanised and have low rates of literacy, access to water and sanitation, and presence of household amenities,” the researchers wrote in the paper. They observed that “with a higher tribal population”, these “hot spots” have been “at the lower end of various health, education, economic and population growth indicators”.
Azhar told The Indian Express, “Rural places show more vulnerability than urban areas due to less electricity, less water supply and other parameters that were assessed to arrive at the HVI. However heat action plans are focused for urban centres, and hence the study urges more interventions.”
Technically, a heat wave is declared if the maximum temperature rises above 40 degree Celsius for 2 consecutive days and is at least 4.5 degrees Celsius above normal, or when the maximum temperature exceeds 45 degrees Celsius for 2 days. In hilly areas, temperatures must rise above 30 degrees Celsius with a departure of at least 4.5 degrees Celsius.
A “severe heat wave” is said to prevail when, for 2 consecutive days, the maximum temperature exceeds 40 degrees Celsius and the departure from normal is at least 6.5 degrees Celsius. It can also be declared when the maximum temperature goes beyond 47 degrees Celsius.
India saw 1,100 heat-related deaths in 2016, and more than 2,200 in 2015. Most states do not report the deaths and very few cities have heat action plans, said Dr Mavalankar, who was instrumental in Ahmedabad adopting a heat action plan, and becoming the first South Asian city to inform citizens about extreme weather and of ways to take necessary action. In 2010, Ahmedabad faced a severe heat wave, and 274 cases of heatstroke and 65 deaths; by contrast, there were 57 cases of heatstroke and 11 deaths in 2015, after implementation of the heat action plan.
“Creating and mapping a heat vulnerability index is a useful first step in protecting the public from the health burden of heat,” says the study. The index, Mavalankar said, can be used by planners, policymakers, and disaster mitigation experts.