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Heat stress occurs when the body is unable to cool itself down to a healthy temperature.(1) The risk of developing heat stress is increased by the use of personal protective equipment (PPE) in a warm or hot environment and this is of particular concern during the summer months.(2) The individual, the environment, the rate of work and the type of PPE used are all contributing factors to the risk of developing heat stress. PPE also increases the risk by reducing a person’s ability to adjust clothing to help regulate body temperature and interfering with the body’s usual thermoregulation mechanisms.(2)
Heat stress can present as heat exhaustion which can lead to heat stroke. Heat stroke is when the body temperature becomes extremely high and the body can no longer cool itself down.(2)
What is thermoregulation?
Thermoregulation is the process by which the body maintains the core internal temperature. For an average person the core temperature is between 37°C and 37.8°C. The body’s ability to function is affected if the body temperature deviates greatly from this average. A body temperature of 42°C can, for example, result in brain damage or even death.(3)
The body has the ability to help itself cool down in order to maintain its temperature. This is done via the central nervous system, which can sense when the internal temperature changes and send a signal to the hypothalamus to induce change to various body organs, glands and muscles.(3)
The body uses two mechanisms to cool down—sweating and vasodilation.(3) Sweating involves the release of sweat by the sweat glands, which results in the skin being cooled down via evaporation. This helps to lower the internal body temperature. The vasodilation of blood vessels results in more blood flowing to the skin, where it is cool and away from the core, where it is warm. This helps to reduce the core temperature through the release of heat by radiation.(3) The body’s ability to use these two mechanisms is reduced by the use of PPE.(2)
What are the symptoms of heat exhaustion?
Heat exhaustion can present as:(2)
- Pale appearance
- Excessive sweating
- Decreased appetite
- Clammy skin
- Muscle cramps
- Increased breathing and pulse rate
- Body temperature of either 38°C or above
How is heat exhaustion treated?
If a person is showing signs of heat exhaustion, their body temperature needs to be reduced. This can be done by:(4)
- Moving them to a cool area
- Drinking fluids, such as water or rehydration drinks
- Lying the person down and slightly raising the feet
- Spraying or sponging the skin with water to help cool the skin
- Cold packs can also be used around the neck or armpits
If effective, the person should start to feel better within 30 minutes.(4)
How can you reduce the risk of developing heat stress?
To reduce the risk of staff developing heat stress, workplaces should implement a plan. Premises should be assessed for the risk of overheating and control measures, such as removing sources of heat, put in place. Workplaces should sign up to alerts like the Public Health England/Met Office heat health alerts, so they are aware when high temperatures are forecast. Awareness of the heatwave plan for England is also advised.(2)
For those working in warm or hot environments and wearing PPE the following measures are advised to help reduce the risk of developing heat stress:(2)
- taking regular breaks to keep cool and drinking enough fluid to maintain hydration: checking urine for hydration levels is an easy way to monitor this, if it is dark or strong smelling more fluids should be consumed
- having an awareness of what heat stress and dehydration are, including symptoms and how to manage it
- teaming up with someone to monitor each other for symptoms
- resting between shifts and keeping cool.
More information on PPE and heat stress can be found on the Public Health England website.
- Health and Safety Executive (2020) Heat Stress
- Public Health England (2020) Personal protective equipment and heat: risk of heat stress
- Healthline (2016) Thermoregulation
- NHS Conditions (2018) Heat exhaustion and heatstroke