FST JOURNAL

There is hardly a day goes by without a headline of some record-breaking bushfire, flood or temperature.  It is quite amazing that they do not evoke an urgent response from people: instead they seem largely accepted or ignored.  Perhaps climate change is still seen as something that is going to happen in the future, as opposed to more immediate problems like the energy crisis. 

Yet these events that are happening now entail substantial costs, about £1.5 billion pounds of damage for each of the 10 extreme events that occurred in 2021.  The health costs for malaria, diarrhoea, malnutrition and heat are predicted to reach between £2-4 billion pounds per year by 2030. 

The Physiological Society is active in this area and has published a report on the impacts of climate change¹.  It covers heat exposure for workforces and other under-researched groups.  People are going to be working in more extreme conditions and that results in a decrease in productivity.  Looking at the thermoregulatory responses of flood rescuers, the one-in-100-year flood is now happening every two or three years and it is predicted that rescuers working in the warm conditions where they often occur can suffer from heatstroke within about 45 minutes.  In areas of deteriorating air quality, there is a 54% increase in deaths associated with heat exposure and high ozone levels. 

When the air temperature exceeds 30˚C, there is a nearly 70% increase in the number of drownings.  This may be counter-intuitive, but it happens because people choose to leap into cold water to cool off.  The water is often still cold enough to induce all the physiological responses that result in drowning. 

Food safety, biodiversity, mental health and wellbeing are other areas The Physiological Society has examined in a further report on policy issues².  The challenges include: increased average temperatures; extreme weather events; pollution; and disease.  Physiologists are looking at ways to improve the situation with the priority on mitigation. 

Heat waves

In high-income countries, people have lost their thermal resilience.  They spend 90% of their lives living indoors and use about 30% of primary energy sources to keep that indoor environment comfortable in terms of ventilation, heating and air-conditioning.  

Why do people in middle- and low-income countries manage much better in warm weather?  The answer is twofold.  The first point is behavioural adaptation, people know what to do and so change their lifestyle accordingly.  Second, they are much more thermally resilient.  In countries like the UK, we consume energy and resources to remain ‘thermostatic’: we do not tolerate or acclimatise to changes in the thermal environment. 

Looking at the impact of heat waves, there are a number of health problems associated with being exposed to heat, including increased cardiovascular strain and clot formation.  For vulnerable populations such as the elderly, once the air temperature exceeds 26˚C, there is an increase in the number of heat-related deaths.  Children are also vulnerable, because they heat up quickly.

The mechanisms of those particular problems are known: a combination of cardiovascular stress, dehydration and, in heat stroke situations, multi-organ failure.  The neurophysiology and vascular physiology associated with these problems is known but more information is required about, for example, chronic exposure in specific populations such as children, the elderly, pregnant women, the disabled and people with co-morbidities. 

We understand what evokes thermoregulatory responses and how this creates sensations of thermal comfort, heat and cold.  We also understand how these relate to the local environment in terms of radiant heat load, air movement, absolute temperature and humidity: it is possible to manipulate these so as to minimise energy costs and still retain comfort.  By understanding how the body works (‘physiology’), it is possible to reduce a person’s dependence on energy-consuming technology, while improving thermal comfort. 

Thermal comfort 

As an example of the above, if air velocity across the skin is increased, the ambient temperature thermal comfort threshold can be raised by 3-4˚C. This reduces the reliance on air-conditioning. 

Research at Berkeley in the US looked at setpoint temperatures in different US states and cities.  Changing the setpoint of the thermostat from 24˚C to 25˚C gives a 7-15% saving in energy use.  Just changing the airflow from a 30% minimum airflow to 20% provides a 17% energy saving.  These behavioural adaptations can have a significant impact on energy consumption and greenhouse gas emissions.  All of these measures are, of course, based on an understanding of human physiology. 

The same understanding can be used in the design of the urban environment, determining what will be acceptable to individuals and how to retain levels of thermal comfort.  This will involve collaboration between a range of specialists, from botanists, physiologists and medics to architects and town planners – a whole range of different skills coming together to create smarter, cooler, urban spaces. 

One of the reasons why there are more deaths during heat waves in urban environments is because they do not cool down overnight.  The ‘heat island’ effect means temperatures stay high so people have deteriorating sleep which has knock-on effects for their health. 

Policy 

The policy priority is to use our understanding of physiology – and the consequences of disturbances to physiology – as the first step in attempting to mitigate and adapt to climate change.  As with many other societal challenges, understanding how the body works is critical for optimising the response to climate change. 

A multidisciplinary approach (and suitable funding models) will be required to address the health challenges of climate change.  Policy makers in the UK should be making decisions to keep people in the UK safe – as an immediate policy action – while supporting other countries as well, through research and funding.  In terms of media policy, the Physiological Society has called for the Government to name and rank heatwaves.  We already do that with storms, but heat waves kill many more people. 

There is plenty of evidence from the LSE, Oxford and various universities around the globe that naming and ranking heatwaves improves focus, improves coordination, is very good for public awareness and understanding and, in addition, promotes behavioural modification.  In the short term, an important first step is to get people to appreciate the threat and change the way they behave. 

1. Physiology and Climate Change. https://static.physoc.org/app/uploads/2021/11/01082431/Physiology-and-Climate-Change-October-2021_WEB.pdf 

2. The Climate Emergency: Research Gaps and Policy Priorities. https://static.physoc.org/app/uploads/2022/07/12080835/Climate-Emergency-Research-Gaps-and-Policy-Priorities-Report.pdf