Heatwave: Four key points for keeping cool in hot conditions

Record-breaking temperatures are being logged across the UK but research by Loughborough University can help you stay cool(er) and more importantly safer during the July heatwave.

The following tips are from a paper published in the Lancet, which involved analysing the habits of more than 400 million workers from 40 different occupations across Europe.

Researchers found that single, prolonged heat exposure increases the chances of kidney disease and acute kidney injury, with 15% of those exposed to frequent heat stress suffering from these conditions, likely induced by persistent dehydration.

The project, HEAT-SHIELD, is a large project funded by the European Union’s Horizon 2020 Research and Innovation programme.

While the aim of the project is to increase the resilience of European workers to heat, the cooling advice, validated over the last two years, applies to the general public too.

To help protect yourself and others during the incoming heatwave, the team raised four key points:

•             Drink adequately throughout the day and if you are sweating, replace salt losses

While it is difficult to offer specific guidelines on the volume of fluid you should intake, an upper limit of 500 ml/hour is generally recommended with persistent heat exposure and low physical activity. Drink little and often throughout the day to avoid dehydration. Try to drink two cups of water before sleeping to remain hydrated while you sleep. If you exercise hard and for long periods you may need more water but given the risk of over-drinking, you should consult an expert for this.

•             In typical UK heatwave conditions, a fan is always effective in keeping you cooler, especially if you keep your skin wet

There exists some debate among the general public about when fans should be used during a heatwave. In the UK, fans should always be used indoors, unless the indoor temperature is above 34°C. Fans use about 50 times less electricity than air conditioning units!

•             Wet your skin

The normal reaction to heat is to sweat, but there is nothing special about the sweat that appears on our skin. The evaporation of sweat from the skin surface provides an enormous cooling effect, but uses our own body water supply, so can cause dehydration and electrolyte losses. Simply applying water to the skin with a spray, or flannel, mimics the powerful cooling effect of sweat evaporation and will preserve body water. Even lukewarm water will do the trick, but cool water will provide some extra benefit!

•             Ensure you cool down at night

The night-time should always provide respite from the effects of heat during a hot day. However, houses can trap heat during a hot day, not allowing crucial recovery time. If your house tends to remain warm in the night, open windows as soon as the sun goes down, if you think it is safe to do so. Use the fan guidelines mentioned above and wet the skin if necessary. Having some air movement helps you to cope with the warmth.

Apart from the outcomes of the project, there are several general advice points that you should consider for coping with the heat:

  • Wear light, airy clothing. Discuss with your employer whether your work attire can be adjusted to the heat.
  • Apply sunscreen outdoors. If you get sunburned, your sweating system works less efficiently causing increased risks of exercising in the heat.
  • Avoid going outside in peak heat hours
  • Adjust your work or sports activities to the higher temperatures. Do not exercise outside in peak heat hours.
  • If outdoors, stay in the shade and keep your house cool by ventilating at night and in the morning (where this can be safely done), but then closing curtains to avoid peak heat and the sun shining in and heating it up. External shades work best. If your house is badly insulated it may get very hot and stuffy. In such cases, opening windows on the shady or both sides would allow airflow which can improve comfort. Use a fan!
  • When going to the toilet, check the colour of your wee. If this gets darker than normal, you may need to drink more. If you drink a lot, you may need extra salts. These can be added to your meal.
  • People who are using medication may be more vulnerable to heat illness as many affect the thermoregulatory system. If you are a carer, this may be relevant to consider.


Notes for editors

Press release reference number: 19/109

In this study, ‘deadly heat’ refers to temperatures of 40.6°C and above in the Heat Index.

The Heat Index, or ‘apparent temperature’, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

There is no universally agreed "deadly" heat threshold but 40.6°C in the Heat Index is a commonly used value used by the US National Weather Service, amongst others, to identify periods of potentially dangerous conditions.

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