'Integrate health, physiology to assess heat impacts'

When we think of extreme heat, the discussion often focusses only on the mortality it causes. However, it affects individuals differently. JOY MERWIN MONTEIRO, assistant professor at the Department of Earth and Climate Science at the Indian Institute of Science Education and Research, Pune, is studying how a combination of environmental and individual factors determine the risk of heat-related health impacts. In an interview with HIMANSHU NITNAWARE, Monteiro discusses the concept of heat strain—the physiological burden extreme heat places on the body—and why understanding it is crucial to safeguard the population. Excerpts:

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How does extreme heat impact India?

Even though India is intuitively perceived as a hot country, we lack a quantitative understanding of its actual impact on our people. Over the past 10-15 years, epidemiological studies have established that extreme heat contributes to mortality in certain cities and regions. Heatwaves in 2010, then in 2015 and 2019, made headlines due to clear links with mortality. However, heat stress affects us throughout the warm season and likely during the monsoon as well, which is particularly uncomfortable in northern India. It impacts physical work capacity, mental health, crop growth and, through reduced labour productivity and agricultural yields, overall economic output. Heat-related illnesses often go unnoticed, even though most of us have likely seen domestic workers or those ironing clothes fall ill during the summer. Lifestyle changes have also increased our susceptibility. As more people work indoors and lead sedentary lives, acclimatisation to heat has declined. Additionally, lifestyle-related diseases such as cardiovascular diseases and diabetes heighten vulnerability. Studies show India accounts for nearly half of the world’s labour productivity loss due to heat stress. It is time the country examined heat’s impact not only on mortality but also on health, productivity and the economy as a whole.

Wet-bulb temperature and humidity are often used to assess heat impacts, especially with respect to climate change. How crucial are these parameters?