- A study conducted in Delhi’s informal settlements found that high temperatures cause significant economic losses and health impacts for the informal sector workers.
- As temperatures rise, expenditures on essentials such as medicine, ice, and water, also surge.
- Researchers highlight the urgent need for policies to protect informal workers from the severe impacts of extreme heat, which is expected to intensify with climate change.
Heat waves and prolonged heat stress result in income losses and poor health for workers in informal sectors in Indian cities, a new study finds. The study examined 396 workers living in two informal settlements in Delhi, during the peak heat of May-June 2019 and found significant economic losses and health impacts due to high temperatures.
Delhi, in recent years, has been experiencing increasingly severe and prolonged heat waves. The summer of 2024 broke records as temperatures exceeded 49°C in the day and minimum temperatures hovered around 36°C, providing little respite and causing widespread health issues.
Urban areas like Delhi are especially vulnerable to extreme temperatures, says Saudamini Das, professor at the Institute of Economic Growth (IEG), Delhi, and one of the authors of the study published in Environment Research Letters in November 2024.
Heat wave and Delhi’s informal settlements
According to India Meteorological Department (IMD) data, 37 cities across India recorded temperatures over 45°C during the heat wave of 2024. Health ministry sources reported that between March 1 and June 18, 2024, about 41,000 people were affected by heatstroke, with over 100 fatalities due to extreme heat.
The Delhi study conducted by Das and E. Somanathan, Professor and Head of the Centre for research on the Economics of Climate, Food, Energy, and Environment at the Indian Statistical Institute (ISI), Delhi, looked at both maximum temperature and ‘wet bulb’ temperature’ that combines heat and humidity and is an indicator of the degree of discomfort.
The participants of the study, either self-employed or on daily or piece-rate wages, included launderers, construction workers, painters, or manual labourers, cycle- and electric rickshaw drivers, auto drivers, taxi drivers, food vendors, street vendors, traders, fruit sellers, waste and scrap dealers, roadside barbers, cobblers, and roadside mechanics.
The impacts, the researchers report, include income losses, health impacts such as loss of sleep, increased expenses due to requirement for more water, ice and increased visits to doctors. A 1°C rise in maximum temperature results in a 14% drop in net earnings, while a similar rise in wet bulb temperature reduces net income by 19%. During the two heat waves that occurred in the study period of a month, the workers’ earnings were 40% lower than on the other days, the study found.
Workers reported sleep loss of 16%-22%, leading to fatigue and absenteeism. The primary reason for missing work was heat-related illness, and not the lack of available work, the authors highlight.
Also, as temperatures rise, expenditures on essentials such as medicine, ice, and water surge with costs increasing by 14.4% per degree rise in temperature.
The researchers used World Bank data on informal sector employment to conclude that over 320 million informal-sector workers in low-income and lower-middle-income countries are currently exposed to temperatures similar to those observed in the study.
Read more: [Illustrations] Why are temperatures within a city’s neighbourhoods different?
Interventions to beat the heat
The Delhi study adds to findings from other studies on the impact of heat waves and innovative techniques to beat the heat.
Researchers at the non-profit Indo-Global Social Service Society (IGSSS) which works on creating sustainable livelihood opportunities and climate-resilient communities, reported preliminary findings from a pilot study in Delhi, conducted between April 2022 and March 2023, on the use of panels made of waste straw from fields as heat insulators on walls. The study aimed to identify and address the impacts of heat waves through a combination of structural and non-structural preparedness measures, specifically tailored to the needs of the urban poor to reduce the impact of heat waves, especially those living in densely populated settlements in urban areas.
The panels were treated to become fire – and termite-resistant, reported Kolkata-based Proshin Ghosh, thematic lead, climate change and adaptation at IGSSS. Thirty houses were fitted with the panels on the walls, and the inhabitants reported significantly cooler rooms, said Ghosh.
Most of the houses in urban informal settlements are constructed with fragile construction and combustible materials including asbestos and tin roofs, explained Ghosh. Due to poor ventilation, heat builds up during the summers, reaching an indoor average of 35-40°C temperature. People living in congested, poorly-ventilated settlements, especially children below 12 years and the elderly, suffer from acute dehydration, irritability, lethargy, weakness, fever, heat rashes and heat stroke.
In a separate study, researchers at Ahmedabad University, led by Darshini Mahadevia, professor at the School of Arts and Sciences, recently conducted what they described as “an exploratory study” to assess whether built environment characteristics, with emphasis on cool roofs introduced in houses in the informal settlements in Ahmedabad have improved thermal comfort in these dwelling units. They also wanted to assess whether such an intervention, if successful, could help mitigate the health impact of heat.
“In cities of the Global South, low-income housing such as squatters, slums, and other informal housing is more vulnerable to heat stress than formally built housing, due to crowded living conditions, low-quality housing, with inadequate ventilation, and limited access to cooling in the former,” their report says.
Other factors that aggravate the heat stress include the use of heat-trapping materials such as tin, asbestos, cement sheet, plastic, cardboard, plywood scraps, and polyvinyl chloride or PVC, especially for roofing; the use of cooking stoves; absence of greenery and tree shade around the houses; lack of reliable water and electricity supplies; and their location often near industrial areas. Given that moving into more formal houses takes time and money, “modifying housing is an important immediate local-level adaptation intervention to heat and building short-term resilience to climate change,” the report states.
The Ahmedabad study looked at 120 households living in the informal sector in the city to assess the impact of using “cool roofs” – roofs coated with a heat-reflecting paint, or adding bamboo layers at the top, or installing thermocol sheets or cardboard below the roof– along with other measures such as open ventilation and green spaces near their settlements, as a mechanism to adapt to extreme heat and reduce the health impacts of extreme heat.
On average, the difference between the outside and inside temperatures in houses with cool roofs is 5.39℃, while the difference without cool roofs is lesser, 4.20℃, the researchers reported. If the houses had a storey above, or cross-ventilation, or a tree adjoining, a roof higher than 10 feet, and shaded street, these led to reducing temperature inside the home or dwelling unit (DU) compared to only ground-floor DUs, DUs without cross-ventilation, no adjoining tree, a roof lower than 10 feet, and direct sunlight hitting the streets and walls.
Read more: What if we designed homes to stay cool?
Another preliminary experiment with anganwadis or childcare centres in Thiruvananthapuram in Kerala, using cool roofs, coated with white reflective paint, showed that maximum temperatures were lower by as much as 5℃ indoors, Benston John, assistant professor at St. Stephen’s College, Delhi, reports.
Other initiatives across India are working on improving the informal housing structures in informal settlements in urban areas to cope with heat stress. For example, the Gujarat Mahila Housing Sewa attempted to validate some of the cool roof designs and improved ventilation solutions, in collaboration with the Indian Institute of Public Health, Gandhinagar, and the U.S. non-profit, National Resources Defence Council. The interventions included a modular roofing system (Mod Roof), a waterproof roofing made of paper waste and coconut husk as an environment-friendly alternative to the reinforced cement concrete; “air lite ventilation sheets”, or fibre sheets with a dome-shaped structure in the middle with small opening that ensures circulation of air inside, which are installed on the roof to allow daylight and airflow into the house; and solar reflective white paints; and thermocol sheets under roofs. The researchers found that thermocol-insulated roofs recorded the lowest surface temperature.
The Tata Centre for Development (TCD) at the University of Chicago, Energy Policy Institute at the University of Chicago (EPIC-India), and University of Chicago Energy and Environment Lab has partnered with the Mahila Housing SEWA Trust to evaluate the effectiveness of using heat-reflective paint on roofs in lowering indoor temperatures in a study on Delhi’s informal settlements.
Policy implications
Beyond cool roofs and walls is the need for change in some aspects of India’s climate policy, said participants at a heat wave adaptation interventions workshop for slum dwellers held in Delhi in November, to discuss the IEG study findings and adaptation interventions in informal settlements in cities. “We have to plan for a future with increase in heat waves,” and given that a large population of urban India lives in slums, there is a need to “think of mainstreaming urban slums and the informal sector in climate change policies,” Somanathan shared.
Experts also pointed out that master plans for cities such as Delhi would need to incorporate changes to seamlessly integrate informal settlements with green and blue spaces. “There is an underlying design problem of urban India, which we need to address,” Lavesh Bhandari, president and senior fellow at the Centre for Social and Economic Progress (CSEP), a Delhi-based public policy think-tank, told Mongabay India. This involves creating green areas, ensuring water supply and public transport in slums, he stated.
Das and Somanathan’s study itself highlights “the urgent need for policies to protect informal workers from the severe impacts of extreme heat, which are expected to intensify with climate change,” Das highlighted at the Delhi workshop. Experts also recommend providing income support to the informal sector to buffer losses incurred during heat waves; access to affordable health care and basic supplies such as water and ice; and setting up shaded areas and cooling centres for outdoor workers.
Banner image: Many houses in informal settlements in urban India are made up of materials like asbestos and tin which offer poor ventilation and build up heat, leading to average indoor temperatures of 35-40°C in the summers. This view of a Delhi settlememnt was captured in 2012. Image by Michal Huniewicz via Wikimedia Commons (CC BY 3.0).
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