Heat Stress – Managing the risks of working in heat

Who is at risk for heat stress?

Heat stress and the development of heat-related illness can affect any employee an organisation’s heat stress management including policies and protocols are not adequate.

The presence of the following risk factors can increase the risk of developing heat stress and heat-related illness:

• Environmental conditions – location, outside temperature, ventilation
• Dehydration – one of the most important risk factors
• Increased activity level
• Poor acclimatisation
• Previous heat-related illness
• Certain medications
• Presence of health conditions.

Unsuitable environments can increase the risk of developing heat-related illness. Commonalities found within these environments include:

• Working in confined spaces
• Limited ventilation within the work environment
• Heat-retaining PPE use
• Outdoor environments and working during the peak heat of the day
• Strenuous, physical work
• Multiple radiant heat sources
• Remote, uncontrolled or unpredictable environments
• Long working hours or high concentration of work
• High temperature working conditions.

Some of the more common industries that are affected by heat stress at work are:

• Mining
• Emergency services
• Military
• Construction
• Airport workers
• Agriculture

What is Heat Stress?

Heat stress is the body’s inability to adequately maintain a normal temperature in heat causing heat-related illness. Despite attempts to maintain thermoregulation, the body is no longer able to sustain a normal body temperature of 37 degrees. Heat builds up in the body and can cause symptoms ranging from mild to severe.

Examples of heat-related illness include:

• Sunburn
• Heat rash
• Heat oedema
• Heat cramps
• Dehydration
• Reduced cognitive ability
• Syncope (blackouts)
• Heat exhaustion
• Heat stroke
• Death¹.

How does the body regulate body temperature?

Normal body temperature is 37 degrees Celsius but can vary by 0.25-0.5 degree C between individuals². Control of body temperature (thermoregulation) is achieved through internal and external mechanisms. The hypothalamus, an area deep within the brain, is the main control centre of thermoregulation. It monitors internal temperature changes and any small increase in temperature, the hypothalamus responds by:

• Increasing blood flow to the skin
• Increasing sweat production
• Reduction in metabolic rate (the rate of energy the body produces)
• Behaviour changes – reduction in movement, adopting an open body position, reducing appetite³.

As individuals, we also can take actions to feel cooler and lower our body temperature by:

• Removing ourselves from the heat source – finding shade, moving into a cool area
• Ceasing heat generating activity – stopping exercising, working
• Removing clothing
• Turning on the aircon, having a cold shower.

How to identify heat-related illness?

Symptoms can range from mild to severe and some employees may not notice or address the early stages of heat-related illness due to work-related factors including workload, focus and deadlines. Symptoms can include:

• Tiredness
• Thirst
• Irritability
• Bright or dark urine
• Loss of appetite
• Headache
• Nausea/vomiting
• Weakness
• Lightheaded-ness/dizziness/fainting
• Profuse sweating
• Painful muscle cramps (legs and abdomen)
• Weak and rapid pulse
• Hot, dry skin, possibly not sweating
• Fast and shallow breaths
• Confusion
• Vomiting or diarrhoea
• Loss of consciousness³.

It can be useful when working in high-risk environments to have a buddy to help monitor for any symptoms.

How to treat heat-related illness?

For all heat-related illness, simple measures are most effective and include:

• Removal from hot environment into a cool place
• Remove excess clothing
• Increase appropriate fluid intake with small sips avoiding alcohol or caffeinated drinks as they can increase fluid loss and ones high in sugar
• Rest and lie down if necessary for a period of time before returning to the activity
• If needed, try and cool down the body with a cold shower, use a fan
• Seek medical attention if feeling unwell or if symptoms aren’t improving.

How to reduce the risk of developing heat-related illness?

Identification of risk factors is key in reducing employees affected by heat stress and subsequent development of heat-related illness. Risk factors can be grouped by the following:

• The type of work being done
• The characteristics of the worker
• The workplace and associated environment.

Using a standardised framework is key to ensuring risk management measures are robust and effective:

• Identify the hazard
• Assess the risk
• Control the risk
• Review the control measures.

To assess the risk of heat stress exposure uses a three-tiered approach:

1. Basic thermal risk assessment – state of acclimatisation, state of acclimatisation, work demands, location, clothing, sun exposure, hot surfaces, task complexity, air movement, ambient temperature
2. Quantitative risk assessment using environmental and personal parameters – dry bulb and globe temperatures, relative humidity, air velocity, metabolic workload, PPE/clothing insulation
3. Physiological monitoring – core temperature, heart rate, hydration levels (saliva osmolality, urine specific gravity) and recovery rate.

Three key areas require consideration and include 1) the task being undertaken, 2) the individual and their health and 3) the environment².

How can heat hazards be managed?

Managing the risks of heat hazards is addressed by using the Hierarchy of Control; elimination/substitution, engineering controls, administrative controls and PPE use.

Examples include:

• Elimination/substitution – cancelling certain tasks, rescheduling tasks to cooler parts of the day, using electrical equipment rather than those using combustion fuel
• Engineering controls – use of fans, blowers, chillers, insulation or shielding (tents and shade)
• Administrative controls – training and education, acclimatisation schedules, worker medical assessment, worker physiological monitoring, work rest regime
• Personal Protective Equipment – ice or cool vests, appropriate clothing for the environment⁵

How does heat-related illness affect organisations/why is this important?

Heat-related illness can result in increased fatigue, impairment of cognitive function and fine motor skills, incidence of physical injury including death, reduction in workplace productivity and increased costs¹.

By protecting workers in high-risk heat stress environments maintains employee trust in the organisation, maintains productivity and reduces costs associated with illness and injury, maintaining organisational reputation.