How Extreme Heat Impacts Public Health

• Heatwaves cause excess deaths, especially among vulnerable populations, with calculations showing significant mortality during heat periods.
• Extreme heat reduces labor productivity, particularly for outdoor workers, leading to substantial economic losses.
• Localized climate data and modeling helps asset managers understand and mitigate the impacts of extreme heat. This data supports decision-making for adapting and retrofitting infrastructure to handle higher temperatures, thereby reducing public health and productivity costs.

On 19 July 2022, the UK recorded a temperature of 40°C for the first time, highlighting the severe public health risks associated with extreme heat.

While the UK, like many other parts of the world, has experienced significant heatwaves in the past, this event could be linked to human-caused climate change.

The unprecedented heatwave of July 2022 serves as a stark warning of the future challenges that both the UK and the global community will increasingly face.

This hot day in the UK pales in comparison to Bahrain, which typically expects 40°C in the next decade’s summers, and Australian cities occasionally topping 50°C – as shown on Climate X Spectra on extreme heat days.

Why is heat so costly to public health?

Calculating heat-related deaths is complex because people die for various reasons all the time. Statisticians use "excess deaths," comparing the number of deaths during a heatwave to the long-term average. However, there is no universal definition of a heatwave, and definitions vary by country and even within regions.

In the UK, a heatwave is defined by a minimum of three consecutive days with daily maximum temperatures at or above specific thresholds, which range from 25°C to 28°C depending on the county.

In 2022, the UK experienced five heat periods from June to August, resulting in 3,271 excess deaths, 6.2% above the average of the previous five years.

The worst period was from 10-25 July, which included the 40°C mark, with 2,227 excess deaths (10.4% above average).

During 17-20 July, excluding COVID-19, England saw 1,012 excess deaths among those aged 65 and older.

Across Europe, an estimated 61,672 heat-related deaths occurred from 30 May to 4 September.

After heat periods peak, deaths often fall below average, indicating that people who were expected to die soon died earlier due to the heat.

Vulnerable populations, particularly those susceptible to COVID-19, also face heightened risks during extreme heat events.

Extreme heat can cause organ failure and dehydration, leading to death.

High humidity exacerbates the problem by making it harder for sweat to evaporate, preventing the body from cooling down. Nights that remain hot further increase death rates as the body cannot recover from daytime heat.

Sunburn, poor air quality from vegetation fires, and other indirect effects also contribute to the health toll.

Plus, people often seek relief from heat in water bodies, leading to an increase in drownings during heatwaves.

To mitigate the risks, it is essential to drink plenty of water, avoid alcohol and caffeine, stay in cool locations during the hottest parts of the day, and check on vulnerable individuals.

One may wonder - could less cold weather due to climate change offsets heat’s lethality?

While fewer cold-related deaths occur due to the changing climate, the increase in heat-related deaths far outweighs this benefit. Projections suggest the UK will see over 4,000 more heat-related deaths per year by the 2050s, compared to 800 fewer cold-related deaths.

Extreme heat significantly reduces labor productivity, especially for outdoor workers.

Research by the "Lancet Countdown" found that from 2013 to 2022, workers in Asia lost an average of 189 labor hours per year due to heat exposure, while workers in Africa lost 161 hours per year.

In 2022, Africa's GDP loss due to heat was estimated at 4.1%.

These losses fall predominantly on outdoor workers.

When it is too hot to tend to crops and livestock, global food chains can be impacted. Farmers and agricultural workers are experiencing loss of income. Construction workers suffering from the heat impact the building and maintenance of built environment assets.

Delivery workers, too, can be impeded, being forced away from bicycles with air conditioning in cars using up fuel and adding to traffic and pollution. In places in Germany, parents are starting to see health impacts when their kids cycle to school in increasingly hot weather.

Indoor workers are frequently affected too.

If a workplace lacks air conditioning, then kitchens and garment factories can overheat, slowing down the workers and reducing their income - or putting them at risk of death. With air conditioning, any workplace and home is susceptible to power outages as people the artificial cooling systems work harder for longer.

Transportation assets are more widely affected. Train tracks buckle in the heat, forcing speed restrictions or, especially if rails must be replaced, cancellations.

Not all public transport systems, such as around Paris and London, are fully air conditioned, with people fainting common during the summer, requiring a medical response and delaying the trains.

Other forms of cooling, such as natural ventilation and mechanical ventilation, have limits - as does opening windows which might merely blow in hot air.

Climate data followed by localised modelling, as offered by Climate X, can provide specific temperature expectations for a particular transportation route or location with indoor and outdoor workers.

Long time series also identify other factors contributing to heat, including the urban heat island effect in which cities are hotter than their surrounding areas.

Paved areas and buildings absorb and emit more heat than green spaces, without offering cooling effects from trees and surface water such as ponds and rivers. Some air conditioners and vehicles also emit heat into the outside environment.

Having the data to estimate all these impacts supports decision-making for adaptation and retrofitting across all infrastructure.

Data is available for all these impacts, including how they are changing, allowing asset managers to understand better continuing extreme heat and its public health costs.

The physical risks and productivity losses from extreme heat and associated humidity can be calculated with Climate X solutions.

Using our climate tech platforms, asset managers can work out the costs and how to reduce those costs through adaptation and retrofitting.