Last reviewed 16 June 2021

Gordon Tranter summarises what employers and employees should know about the potential hazards of working outdoors during hot weather and how to manage them.

The UK hot weather can have both short-term and serious long-term impact on an employee’s health when working outdoors. The risks fall into two main categories: heat-related illnesses and health conditions caused by exposure to solar radiation.

Heat-related illnesses

The risks

Heat, particularly if accompanied by humidity, can be a serious health threat to those working outside during the summer months. Employees working in these conditions can suffer from dehydration and heat stress, which can lead to fatigue, muscle cramps, rashes, fainting and, in severe cases, a loss of consciousness.

Specific heat-related illnesses include the following.

  • Heat stroke: this occurs when the body cannot regulate its core temperature. Symptoms include confusion, fainting, seizures, excessive sweating (or red, hot, dry skin) and a very high body temperature.

  • Heat exhaustion: this occurs when the body loses water and salt due to heavy sweating. Symptoms include cool, moist skin, heavy sweating, headache, nausea or vomiting, dizziness, light-headedness, weakness, thirst, irritability and a fast heartbeat.

  • Heat cramps: follow the loss of body salts and fluids during sweating. Symptoms are muscle spasms and pain, usually located in the abdomen, arms or legs.

  • Heat rash: this is characterised by clusters of red bumps on the skin, which usually appear on the neck, upper chest and folds of the skin. It occurs when pores become clogged and cannot expel sweat.

Assessment of the risks

As a first step to managing the risks from heat during outdoor working it is necessary to assess the likelihood of employees suffering from heat-related illnesses. This should involve considering the followng.

  • Working climate — this includes air temperature, humidity, air movement and effects of working near a heat source.

  • Work rate — the harder the work the more body heat generated.

  • Clothing and respiratory protective equipment (RPE) — unsuitable clothing and RPE that restricts sweat evaporation may result in an insufficient amount of heat being dispelled from the body resulting in the core body temperature rising and the body eventually receiving more heat than it can lose.

  • Age, build and medical factors of the worker — may reduce an individual’s tolerance to heat.

The assessment should include talking to the workers involved and their safety representatives to establish whether they are suffering early signs of heat stress. If they are, help from occupational hygienists or occupational health professionals may be required.

Managing the risks

When employees work outside during hot weather, employers need to introduce some administrative controls. These may include:

  • rescheduling work to cooler times of the day to minimise exposure

  • providing more frequent rest breaks

  • providing free access to cool drinking water

  • introducing shading in areas where individuals are working or taking their rest breaks

  • encouraging the removal of personal protective equipment when resting to help heat loss

  • ensuring that any workers using medication that could increase the risk of heat-related illness are not exposed to a risk to their health.

Workers should be educated about the risks of heat-related illnesses. Steps they can take themselves might include:

  • wearing loose-fitting clothing made of light, breathable fabrics to allow body heat to escape

  • wearing light-coloured clothing to reflect sunlight

  • drinking plenty of water throughout the day to replace water lost through sweating

  • avoiding caffeine and alcohol or large amounts of sugar

  • eating smaller meals before work activity

  • avoiding exposure to direct sunlight

  • limiting physical exertion

  • staying in shaded areas when possible

  • wrapping a wet towel around their head and neck for instant cooling relief.

First aid

If your organisation has employees working outside in hot weather, make sure that first aiders know the risks and early symptoms of heat-related illnesses so they know the steps they should take, as follows.

  • Heat stroke: if a worker develops the symptoms of heat stroke, it is advisable to call 999. While waiting for help, the worker should be moved into a cooler, shady environment, his or her clothing loosened and outer clothing removed. He or she should be fanned with air, and cooled with cool water and cold compresses or ice packs. Fluids (preferably water) should be provided as soon as possible and someone should stay with the worker until help arrives.

  • Heat exhaustion: workers showing the symptoms of heat exhaustion should be encouraged to sit or lie down in a cool, shady area, given plenty of water or other cool beverages to drink, and cooled with cold compresses or ice packs. Medical attention should be sought if signs or symptoms worsen or do not improve within an hour. The worker should not return to work that day.

  • Heat cramps: workers with heat cramp should rest in a shady, cool area and be given water or other cool beverages to drink. The worker should not be allowed to return to strenuous work until after a few hours. If the cramps do not disappear, the worker should seek medical attention.

  • Heat rash: workers with a heat rash should move to a cooler, less humid area and keep the affected area cool and dry. Calamine or lanolin lotions can relieve itching.

Solar radiation

The risks

Too much sunlight can be harmful. Sunlight contains ultraviolet (UV) radiation, which can cause sunburn, premature ageing of the skin, wrinkles, eye damage (including cataracts) and skin cancer. Skin cancer is one of the most common forms of cancer in the UK, with more than 50,000 new cases every year. The risks from solar radiation are greatest during hot weather in the summer but exposure in the rest of the year can contribute to skin damage.

Workers with the following are more vulnerable to the effects of solar radiation.

  • Fair or freckled skin that does not tan, or goes red or burns before it tans.

  • Red or fair hair and light-coloured eyes.

  • A large number of moles.

Employees in these categories who work outdoors for a long time need to take particular care.

Managing the risks

The management procedures for protecting worker from heat-related illnesses — rescheduling work to cooler times of the day, providing more frequent rest breaks, introducing shaded areas — apply equally to protecting workers from solar radiation. The dangers of exposure to solar radiation and sun protection advice should be included in routine health and safety training.

In addition, during outside activities workers should:

  • cover bare skin with lightweight but tight weave clothing, including long-sleeved shirts and long pants and, importantly, keep their tops on

  • wear a hat with a brim or a flap that covers the ears and the back of the neck eyes, forehead, nose and scalp wherever possible

  • stay in the shade when possible, during their breaks and especially at lunch time

  • check their skin regularly for any unusual moles or spots and see a doctor promptly if anything is changing in shape, size or colour, itching or bleeding

  • wear UV-absorbent sunglasses with wrap-around lenses or wide arms with the CE Mark or mention of BS EN ISO 12311:2013.

Sunscreens and sun protection factor

Employers should encourage workers to apply a sunscreen product to any part of the body they cannot cover up. Sunscreen products help prevent UV radiation from reaching the skin.

Two types of UV radiation, UVA and UVB, damage the skin, age it prematurely and increase the risk of skin cancer. UVB is the chief cause of sunburn and plays a key role in the development of skin cancer: while UVA rays, which penetrate the skin more deeply, are associated with wrinkling, leathering, sagging, and other light-induced effects of ageing (photo-ageing). They also exacerbate the carcinogenic effects of UVB rays and increasingly are being seen as a cause of skin cancer themselves.

Sunscreens in the UK are labelled with an SPF (sun protection factor), which is a measure of the amount of UVB protection they provide but not of the protection against UVA. SPFs are rated on a scale of 2–50+ based on the level of protection they offer. Ratings between 2 to 14 provide the least protection and ratings of 50+ provide the strongest forms of UVB protection.

In INDG337 Sun Protection: Advice for Employers of Outdoor Workers, the Health and Safety Executive recommends the use of sunscreen of at least SPF 15. The British Association of Dermatologists advocates the use of a “high protection” sunscreen of at least SPF 30 and, because the SPF ignores any damage caused by UVA rays, the use of a broad-spectrum sunscreen that provides protection against both UVA and UVB rays.

It must be emphasised that even the strongest sunscreen should not be expected to remain effective longer than two hours without reapplication.

Don’t forget the drivers

Drivers can be overlooked because they may not be treated as indoor or outdoor workers. However, the TUC report Cool It points out that workers whose job involves driving can also suffer from fatigue, giddiness, or fainting in hot weather and be a major risk to both themselves and other people.

Employers should provide cars, vans or lorries with air conditioning and ensure it is in working order and, if a driver is likely to be stuck in traffic for any length of time, make sure they are not driving in very hot weather. Establish procedures for ensuring they always have drinking water to hand and what to do if they feel unwell.