Are heatwaves really that harmful?

The UK’s summer heatwave this year was the longest recorded since 1976. On 27 July, the hottest documented temperature was 35°C in Heathrow – not far off the UK’s highest ever recorded temperature of 38.5°C in Kent during August of 2003. Sun worshippers will be pleased to know that more heat is expected, with as many as eight more hot periods predicted over the remainder of the summer.

There are undoubtedly some benefits to being in the sun – increased serotonin levels make us feel happier and increased Vitamin D strengthens bones, teeth and muscles – but how does the heat affect our bodies and what can we do to make heatwaves more bearable?

Increased serotonin levels make us feel happier and increased Vitamin D strengthens bones, teeth and muscles

Heatwaves can trigger a public health emergency. Temperatures in Spain and Portugal this week have reached record-breaking highs of 48° C, resulting in the deaths of three men. Ultimately, such high temperatures are dangerous – they can cause many health issues ranging from depression to heart attacks, to death.

High temperatures affect the body’s ability to thermoregulate. There are mechanisms in the human body that try to keep our core body temperature within a normal range; in the brain, the hypothalamus acts as a biological thermostat. Using nerve cells that sense a rise or fall in body temperature, the hypothalamus acts to try to keep us no higher than 37°C (the average body temperature) as this is when health problems might begin.

Ultimately, such high temperatures are dangerous – they can cause many health issues ranging from depression to heart attacks, to death

As bodily temperature increases, the body tries to cool us down. We might find it annoying or embarrassing to be sweating heavily during a heatwave, but sweating has a crucial function in regulating body temperature; water absorbs heat, so as sweat evaporates, it liberates heat to cool us down. Allowing sweat to drip off your skin or wiping it away with a towel, therefore, means you won’t actually benefit from the cooling mechanism of evaporation.

While heat affects us all, the most vulnerable groups are children, babies, and people with chronic health conditions. Children and babies are unable to take steps to protect themselves, such as limiting how long they spend in the sun and ensuring that they drink more water in hot weather. People with conditions such as diabetes and hypertension are also at higher risk as they might be taking diuretics, expending more fluid.

Sweating has a crucial function in regulating body temperature; water absorbs heat, so as sweat evaporates, it liberates heat to cool us down

When the body reaches 40°C, our physiological coping mechanisms are no longer sufficient and this is when heat becomes particularly dangerous. Hyperthermia,  otherwise known as heatstroke, is considered a medical emergency. Symptoms include fatigue, fainting, delirium, and seizures. Someone suffering heatstroke must seek shade, rehydration and rest, otherwise, the condition can ultimately be fatal.

So what can we do to protect our bodies? In its guidance for preparing for heatwaves, Public Health England suggests the following steps:

1. Keep out of the heat as much as possible, particularly during the hottest part of the day – usually 11am and 3pm.
2. To protect your skin from harmful radiation from the sun, apply sunscreen and wear a hat.
3. Always carry water when travelling to help rehydrate your body.

Someone suffering heatstroke must seek shade, rehydration and rest, otherwise, the condition can ultimately be fatal

Heatwaves are expected to become more frequent – current estimates show that the ‘extreme temperatures’ of the 2003 heatwave are likely to be considered normal summer temperatures by 2040. By then heatwaves will also be longer and more intense. Anthropogenic activity has already resulted in more frequent heatwaves than previous years – the blistering heat and discomfort we are currently experiencing should remind us to take steps to reduce carbon emissions in order to avoid making the situation even worse in the future.