Extreme Heat Is Becoming a Workplace Hazard: Interview with Tarun Khanna

As record-breaking heat becomes more common around the world, with temperatures shattering records this spring from Boston to London, employers are facing new risks from hotter workplaces.

Extreme, longer-lasting heat often leads to more absenteeism, increased cooling costs, lower productivity, and even more employee injuries and deaths, explains Harvard Business School Professor Tarun Khanna, part of an interdisciplinary team of experts from fields including public health, medicine, earth science, and epidemiology.

In fact, as climate change worsens workplace conditions worldwide from farms to factories, the United Nations’ International Labour Organization estimates that 2.4 billion workers experienced excessive temperatures at their job sites in 2020, with heat responsible for 19,000 deaths, 23 million injuries, and $361 billion in productivity declines.

Gig workers and informal employees, such as street vendors, seamstresses, and workers in agricultural fields and factories, especially in economies across the global South, often lack formal workplace protection and return at night to homes as hot as their job sites, which can cause chronic health issues, according to “Responding to Rising Heat in Workplaces and Homes of Low Income Workers,” published in the British Medical Journal in November.

The article, led by postdoctoral fellow Robert Meade at the Harvard T.H. Chan School of Public Health, points to possible solutions, such as buildings with cool roofs and better ventilation, and changes to the workday, like adding rest breaks and water stations and shifting hours outside peak heat times. But those proposals could be costly for workers who lose wages if they pause to rest or need to care for family in the evenings.

The team is also involved in a multi-year study in partnership with the Self Employed Women’s Association and led by Professors Caroline Buckee at the Chan School and Satchit Balsari at Harvard Medical School that uses sensors to track detailed health metrics of about 1,000 Indian women. The researchers then connect that data with temperature readings in the women’s homes and workplaces.

Khanna, the Jorge Paulo Lemann Professor, partnered on the article with Meade, Buckee, and Balsari; Tess Wiskel of Harvard Medical School and Beth Israel Deaconess Medical Center; Peter Huybers and Daniel Schrag of Harvard’s Department of Earth and Planetary Sciences; Jennifer Leaning of Harvard's FXB Center for Health and Human Rights; Rajan Rawal, Sneha Asrani, and Dhruval Gadhvi of CEPT University; Vidhya Venugopal and Tanya Isaac of Sri Ramachandra Institute of Higher Education and Research; Ahmed Shaikh of the Icahn School of Medicine at Mount Sinai; and Felipe González-Casabianca of the University of Tartu.

In an interview edited for length and clarity, Khanna explains the importance of taking action to address heat-related challenges.

Many communities must adapt to a hotter future

“Obviously, climate change is an issue everywhere. In the traditionally developed world, most of the money is going into climate mitigation—stopping it from worsening even further. In rich countries, most of us will survive somehow, but our emissions per person are so high that we're worsening things for the rest of the world quite dramatically.

In most of the rest of the world, the focus has to be on climate adaptation, which is dealing with the fact that the die is already cast, temperatures are rising, and we have to live with it.”

Heat often gets overlooked

“Generally, when people think about climate change, the bulk of the conversation is about sea-level rise. But the other big problem that has become increasingly salient is heat.

The ballpark numbers are that 70% of the world's population works in the informal workforce. And in countries like India, it's probably in excess of 90%. They're not protected from climate change, and certainly not from extreme heat. In places like India and Africa, it is literally unbearable.

You see it anywhere people are exposed to very long hours in difficult circumstances. In the US, we have OSHA [Occupational Safety and Health Administration] rules, so at least legally there is some protection, but in most of the rest of the world, there isn't any.”

Heat can cause cardiac stress and chronic disease

“One of the things I learned is that the immediate impulse is to say, ‘It's really hot. You're in danger of heat stroke.’ It turns out that the effects of extreme heat are far more insidious and long-lasting than heat stroke.

Long before heat stroke occurs, the amount of cardiac stress that your body is under, even with a little bit of heat exposure, is quite high. And that means it's going to affect every system in your body. You're going to have much more manifestation of chronic disease. There were a lot of doctors who said, you really ought to be paying attention to the reproductive health of women, which is one of the places where extreme heat will show up. We had to update our data collection to make sure we were getting those kinds of measures.”

Collecting data can be challenging

“Getting this sensor data in India requires you to have sophisticated monitoring dashboards because you are relying on the cooperation of a thousand informal women workers who are not used to this exercise. You have to pay attention and maintain their buy-in. We spent many months making sure that everybody understood why this was an important program and why this knowledge would contribute to their own well-being and to the common good.

And then if something goes wrong with the data, let's say a woman removes the sensor because she is tired of it or it's bothering her skin, then the data collection is compromised. Somebody needs to go to her house and find out what happened and fix it.”

Heat impacts cognitive work

“When it’s very hot, fatigue sets in very early, so you will have less effort. Mental acuity succumbs, so I don't think it's going to even be limited to blue-collar jobs. It'll affect anything where cognitive work is required. Commuting issues are going to be a big deal. Imagine being in the New York subway system or the tube in London, which is so jammed. With the hot environment, it's not going to be good news.

Recently, there was a heatwave in Paris, where the walls are so thick, they’re not made for heat. There was a lot of mortality for elderly populations because the building structures were not set up for it. And by the time these heatwaves hit, which are happening with greater frequency, it’s too late. Energy costs are going to go up to compensate for this. You're going to have absenteeism. I don't think anyone's going to be immune from it, honestly.”

The study in India could lay the groundwork for solutions

“This is the kind of data that you would need to develop insurance products that cater, for instance, to loss of income due to heat exposure. You can't build an insurance product unless you have data and unless you understand the effects of heat on the workforce and the human body.

What's the effect on lost productivity for workers? The truth is, no one really knows because we've never been in situations where there's so much heat. We're all kind of learning as we go along. And you need to know the basics of the problem before you can start to think about remedies and solutions.”

Photo credit: Russ Campbell