The urgent need to tackle heat stress effects — not just heat — this summer

Heat stress occurs when the body’s natural cooling mechanisms struggle to maintain a normal internal temperature, potentially leading to heat exhaustion or, in severe cases, heatstroke. | Image used for representational purpose only
| Photo Credit: Getty Images

A sweltering April is almost here, and temperatures across India are steadily rising this summer, a year after the hottest recorded year on Earth so far, that also saw heatwaves arrive early and for longer durations.

Heat can have a number of effects on the human body. Experts are now calling for close monitoring of the heat stress index in order to frame policies to safeguard public health.

Heat stress happens when the body cannot get rid of excess heat, causing its’s core temperature to rise, and the heart rate to increase. High temperatures combined with moisture can make it feel even hotter, as increased humidity makes it harder for the body to cool itself through sweating.

A study published in Natural Hazards by T.V. Lakshmi Kumar, who is now with Jawaharlal Nehru University, found that coastal cities in India are more vulnerable to heat stress due to climate change. Cities like Chennai, Nellore, Puducherry, and Kochi are expected to see a drop in work performance in the coming decades. People working in these cities may need longer breaks during work hours to prevent heat-related issues.

Heat-related illnesses, a growing public health concern

Experts note that while the India Meteorological Department defines heatwaves based on temperature, there isn’t enough focus on heat stress, which involves both temperature and humidity. For instance, the wet-bulb temperature, one of the measures that combines both the air temperature and humidity, provides an indication of heat stress on the human body.

While we usually cool down by sweating, when the wet-bulb temperature reaches a certain point, this method no longer works effectively. As a result, our body temperature continues to increase. This marks the threshold beyond which humans cannot adapt to extreme heat. If we can’t escape these conditions, our core temperature can rise to dangerous levels, potentially leading to organ failure.

Vidhya Venugopal from Sri Ramachandra Institute of Higher Education and Research, who studied occupational health risks for outdoor workers, explains that heat stress occurs when the body fails to control its internal temperature.

She led a study on salt pan workers from 2017 to 2020, where many workers reported symptoms like heat strain, dehydration, and urinary tract infections, likely caused by excessive sweating, limited water, and no access to toilets during long shifts. The wet-bulb globe temperature often exceeded safe levels in salt pans during summer. Another study on cashew nut workers also revealed that heat stress takes a heavy toll on them. “It is generally thought that heat stress affects only outdoor workers. That is not the case,” she said.

The need for proactive and localised solutions

A recent study by Sustainable Future Collaborative (SFC) included cities like Surat, Mumbai, Delhi, and Bengaluru. The findings highlighted the need for long-term actions focused on the health system to address the growing risk of heatwaves. Improving health system preparedness is vital, but experts argue that more actions are needed to prevent the effects of heatwaves before they become overwhelming.

Tamanna Dalal, an author of the SFC study, pointed out that important actions, such as providing cooling systems for homes and workplaces, developing insurance for lost work, and improving fire management and electricity grids during heatwaves, are not being fully implemented. Additionally, some cities are lacking critical measures like local weather stations and mapping urban heat islands.

The short-term rapid response guidelines currently being implemented in various States are inadequate and fail to address the full scope of the challenges posed by extreme heat events, the SFC study noted. These guidelines need to be more comprehensive and better tailored to effectively manage and mitigate the impact of heatwaves and related risks, said Ms. Dalal.

Also Read:​Heat plan: On Indian cities and heat-related preparedness

India cannot afford to move slowly

Prof. Venugopal said that heat stress has to be tackled in a serious manner going forward. “While measures have been taken in Ahmedabad, and Tamil Nadu to a certain extent, things are still moving slowly. This is an area where moving slowly can be detrimental,” she added.

Ms. Dalal also noted that heat action plans in many cities are not effective because they lack legal backing. Many departments do not even have a copy of the plans. There is a need for localised solutions for vulnerable groups, and heat action plans should be better enforced and supported, she said.

“We should not think about heat on April 1, as we usually tend to do,” said Prof. Venugopal, and urged governments to plan ahead to ensure prevention of heat-related health complications among the public.