The optimal internal temperature of a human body is ~37°C (± 0.5°C).

At this temperature, the body effectively completes various recovery, growth and repair processes. Slight temperature variations (≤0.5°C) are reversed automatically by self-regulating mechanisms, eg sweating and shivering.

However, such mechanisms may not be able to rectify extreme temperature variations, which can result in widespread behavioural and physiological changes, and at the greatest extreme, organ failure and death.

In-line with global warming, Australia’s average temperature has increased by 1.44 ± 0.24°C since the 1910s leading to various environmental changes, eg increases to fire danger, hot weather records and decreases in rainfall. 

As the surrounding climate continues to warm, it is imperative that Australian businesses implement efficient heat stress prevention tactics to safeguard the health and safety of their workforce.

A hidden risk

The impacts of heat stress on workplace accidents are often an unrecognised and underestimated factor in many workplace injuries.

In 2022, ~1,720 serious claims (where workers were absent for ≥1 working week) related to heat, electricity and other environmental factors. Moreover, data shows that injuries and illnesses associated with thermal exposure have a higher average unit cost compared to the cost of falls, trips and body stress injuries.

Causes of heat-related illnesses

There are many environmental and physical factors that can cause heat stress and heat-related illnesses.

1. Lack of adequate ventilation and airflow – although the body naturally sweats to lower body temperature, this mechanism is not effective if the sweat cannot evaporate from the skin due to restricted airflow.
2. Dehydration – a dehydrated individual is unable to efficiently produce sweat which can result in increases to internal body temperature.
   
3. Humidity – similar to airflow, high humidity can prevent sweat evaporation and aggravate heat strain.
4. Radiant temperature – radiant temperature refers to the temperature of all surfaces surrounding an individual. Individuals tend to feel higher levels of discomfort when they are in closer proximity to windows or equipment that is emitting heat.
5. Clothing – heavy duty industrial clothing and certain personal protective equipment (PPE) can trap air against the skin and prevent sweat evaporation.

Signs of heat stress

Early signs can appear as soon as an individual starts experiencing dehydration and may include:

• Excessive sweating
• Feeling light-headed
• General feeling of fatigue or lethargy
• Painful muscle cramps in the extremities or abdomen region
• Increased irritability

Heat exhaustion – individuals who experience prolonged heat stress can develop heat exhaustion. In addition to the signs above, they may also experience:

• Headaches
• A weakened and rapid pulse
• Nausea and vomiting
• Prickly heat – heat rash that develops when a person sweats more than usual and sweat glands become blocked
• Decreased coordination skills

Heatstroke – is an extreme medical emergency and if not treated immediately can lead to permanent organ damage or, in worst case scenarios, death. Heatstroke occurs when an individual’s temperature rises above 40ºC. In addition to the previous symptoms, heatstroke presents as:

• Flushed and unusually dry skin
• Dry and swollen tongue
• Fainting (syncope)
• Convulsions or seizures
• Disorientation or delirium
• Aggressive behaviour and slurred speech

Risk factors

Individuals can have different heat stress thresholds depending on their age, body composition and health status.

Individuals most at risk are:

• Aged ≤25 or ≥55 years
• Have a BMI ≥3030 mg/m²
• Suffer from chronic health conditions, e.g. heart disease, high blood pressure or lung disease
• Are pregnant or nursing
• Consume medications which inhibit the body’s ability to self-regulate temperature, e.g. blood pressure drugs, chemotherapy drugs or medications for treating Parkinson’s/Alzheimer’s disease

Managing heat exhausation or heatstroke in the workplace

If you suspect that a co-worker or an employee is experiencing heat exhaustion:

• Cease work immediately and lead the individual to a cool and shaded area. If possible, ensure that the area has a fan or an air-conditioner.
• Help the individual lie down – ensure their legs are supported and are lifted slightly off the ground.
• Give the individual cool water to sip on slowly.
• If the individual is experiencing muscle cramps – gently massage the area to ease the pain.

If you suspect that a co-worker or an employee is experiencing heatstroke:

• Call 000 immediately for an ambulance service.

If the individual is still conscious:

• Move the individual to a cool and shaded area (preferably with access to a fan or an air-conditioner).
• Focus on reducing their body temperature – loosen clothing and place cool/damp cloths behind their neck, on their forehead and in their armpits.

If the individual is unconscious:

• Move the individual to a cool and shaded area (preferably with access to a fan or an air-conditioner).
• Place the individual in a recovery position (on their side) and ensure that they are able to breathe.

Prevention strategies for reducing the risk of workplace heat-related illnesses

Instant mitigation strategies

• Schedule physically intense tasks during cooler parts of the day, eg early mornings and late afternoons in warmer months.
• Ensure no employee is working in isolation.
• Provide workers with jackets or vests that have pocket space for reusable ice packs.
• Promote regular water breaks - a small cup (~200 mL) of cool water is recommended every 30 minutes even if not feeling thirsty.
• Promote regular snack breaks to replenish electrolytes lost via sweating. 
• If your workplace has large enclosed spaces, ensure there are adequate mechanical aids, eg fans or cooling units.

Workplace environmental consulting

Occupational physicians (OPs) are specialists in workplace health and take into account their clinical knowledge and the psycho-social/economic impacts of workplace injuries to provide busineses guidance on individual and workforce health and wellbeing.

Our Occupational Physician Consulting Services connects our highly qualified OPs with your workplace for site assessments and environmental consulting. The OP will assess all on-site risks and current risk mitigation strategies and work with your business to devise a management plan that looks after your employees.

Ensure your workplace has an up-to-date heat stress policy

Check out our detailed guide on the nine key elements to consider when creating or assessing your workplace heat stress policy including acclimatisation, self-pacing and medical surveillance.

Educate employees through health promotion tools

Health promotion initiatives can be effective tools for spreading awareness and increasing employee education on several occupational health and wellness topics.

Sonic HealthPlus health promotion programs can be custom-built and developed to suit your workplace’s unique environment and can be run as short-term or long-term campaigns. Work with our Health and Wellness Consultants and our Marketing Team to create and distribute print-ready marketing materials including posters, fact sheets, table talkers and presentations. 

Check out one of our free workplace heat stress posters below!