What Are the Health Risks of Heat Exposure and How Can We Avoid Them?

[This article has been published in "Espai Salut", by la Diputació de Barcelona]

Heat certainly can have damaging health effects and, while there is no need to be alarmist, we should all be aware of the risks

With the advent of hot weather, we begin to receive advice and recommendations on protecting our health. What are these recommendations based on? Can heat really have such a negative effect our health? The answer is that heat certainly can have damaging health effects and, while there is no need to be alarmist, we should all be aware of the risks, follow the recommendations, which are usually simple and based on common sense, and focus on preventing problems.

Temperature Regulation Mechanisms in the Human Body

The human body has to maintain a constant internal temperature of around 36.5ºC. To do this, it is equipped with a series of thermoregulatory mechanisms

As we know, the human body has to maintain a constant internal temperature of around 36.5ºC, regardless of the ambient temperature. To do this, it is equipped with a series of thermoregulatory mechanisms. One way the body controls internal temperature is by moving blood from the centre of the body to areas close to the skin in order to transfer core heat to the environment. Obviously, this mechanism only works when the ambient temperature is lower than the body's temperature, that is, under 37ºC.

Sweating is another control mechanism, as the evaporation of the sweat from the skin reduces body temperature. These, and many other, mechanisms (changes in respiratory rhythm, blood pressure and blood viscosity, etc.) all contribute to maintaining the balance between our internal body temperature and the external temperature. While in healthy young people these changes are well tolerated, in people with more fragile health they can impose additional stresses and trigger acute health problems. 

Who Is At Risk?

People with chronic diseases are more likely to suffer adverse effects on exposure to heat

People with chronic diseases—especially those with cardiovascular, respiratory or kidney conditions, mental disorders, or diseases affecting the nervous system—are more likely to suffer adverse effects on exposure to heat. In patients with mental illness, a number of factors can converge, including the individual's inability to take care of their condition, the fact that heat can cause outbreaks of certain diseases, and the fact that certain medications may interfere with temperature control mechanisms. Older people are also at greater risk because the temperature control mechanisms become less efficient with age. For example, older people lose their sense of thirst and take longer to start sweating. Pregnant women and infants are also at risk.

The Health Consequences of Heat

The most serious consequence of exposure to high temperature is heatstroke

The most serious consequence of exposure to high temperature is heatstroke. Heatstroke occurs when the body's thermoregulatory mechanisms fail and the uncontrolled body temperature rises above 40ºC. This is a very serious condition and, if something is not done quickly, it can lead to death or lasting damage. Fortunately, cases of heatstroke, and particularly heat-related deaths, are rare, and none are recorded most summers.

There are two types of heat stroke:

• The first type affects healthy young people who do intense physical exercise in the sun and continue to exercise despite the onset of symptoms. It occurs most often in athletes, for example people running races on very hot days, and in people who work outdoors and are exposed to the sun.
• The other form of heatstroke affects older adults with health problems.

Heat is responsible for, on average, 300 premature deaths each year in Catalonia

As well as causing heatstroke, high temperatures can also lead to additional stresses in people with health problems, triggering acute events, such as heart attacks, that can lead to premature death. The Third Report on Climate Change in Catalonia reported that heat is responsible for, on average, 300 premature deaths each year in Catalonia. This increased mortality is more common during heatwaves, that is, periods characterised by consecutive days of extreme heat. However, up to 40% of these premature deaths occur on days not classified as heatwaves, so it is important to be cautious whenever it is hot and not just in the case of extreme weather conditions. In 2003, the summer was very hot and it is remembered as one of the most deadly in terms of health, with 8,000 additional deaths being registered in Spain.

Ways of Combating High Temperatures

In 2004, the Catalan authorities drew up a Plan for the Prevention of the Health Effects of Heatwaves (POCS). The implementation of this plan, coordinated by the Health Department of the Generalitat, depends on the participation of various institutions and bodies. Among other measures, the plan provides for the prediction of situations of risk, coordination of available resources, creation of a census of vulnerable people, the diffusion of informative material, and the need for municipal authorities, elder care residences and healthcare facilities to put in place emergency plans for this eventuality.

As explained above, the preventive measures we can implement on a personal level are simple: avoid exposure to the sun on hot days, dress appropriately, drink water regularly (even when you are not thirsty), visit and help people who are sick or living alone, and so on. If you are unable to cool your home, on very hot days it may be a good idea to spend a few hours in an air-conditioned place, such as your local library or shopping centre.

Municipal authorities can also take measures to counteract heat, particularly in large cities, which are affected by a phenomenon called the urban heat island effect

Municipal authorities can also take measures to counteract heat, particularly in large cities, which are affected by a phenomenon called the urban heat island effect. The term "heat island" refers to urban areas that are hotter than the surrounding area, especially at night. They occur mainly because the asphalt and other materials in the built environment accumulate heat and then release it back into the environment. Measures taken to reduce the heat island effect include increasing urban green space, using green roofs, using highly reflective materials for roofs and street paving, and painting buildings white, a traditional solution used in many hot areas of the world.

Climate models predict an increase in the frequency, intensity and duration of heatwaves

In short, heat can affect our health and it is essential that everyone be aware of the risks and follow the simple recommendations for preventing the adverse effects. Likewise, institutions must implement preventive measures and be prepared for emergency situations, taking into account that they could face significant increases in the need for medical care during the summer, a season when it may be difficult to mobilise the necessary personnel. Climate models predict an increase in the frequency, intensity and duration of heatwaves. This means that we must be as prepared as possible to deal with this phenomenon.

You can find more information on this topic at https://citieswewant.isglobal.org