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Heat stress may affect people in all parts of Western Australia during our summer months and may affect workers at some workplaces throughout the year. The effects of heat stress range from discomfort to life threatening illnesses such as heat stroke. Poster
In Western Australia, hot workplaces are common. Heat may come from:
The Occupational Safety and Health Act 1984 requires employers to provide and maintain, so far as is reasonably practicable, a working environment in which workers are not exposed to hazards. This applies to any risk to safety and health, including illness from working in heat.
Heat stress is the total heat burden to which the body is subjected by both external and internal factors. Heat stress causes increased blood flow to the skin, which allows release of heat. Blood is diverted to the muscles if physical work is being performed, resulting in a lower release of heat through the skin.
The body must balance the heat transferred into the body, heat generated in the body and heat coming out of the body.
If the body can’t balance heat inputs, heat stress may lead to heat illness (or heat strain), a physical response designed to reduce body temperature.
Types of heat illness include:
Some people are less tolerant of heat than others and working in hot conditions may aggravate pre-existing illnesses and conditions.
People who are medically unfit, are on certain medications, overweight, have heart disease, are pregnant, abuse alcohol, or are not acclimatized, are at a greater risk of heat illness and should heed medical advice. Acclimatisation takes 7-14 days to take effect, and can be reduced after three days away from hot work and acclimatisation is entirely lost after four weeks away from hot work.
In identifying, assessing and controlling risks associated with heat illness, employers should consult with workers likely to be exposed to heat as well as with any elected health and safety representatives.
The key risk factors to take into account are:
The risk assessment should be carried out by a person competent in heat assessment and may include use of an appropriate heat stress index. A commonly used and recognised index is the Wet Bulb Globe Temperature (WBGT). This takes into account air temperature, radiant heat, humidity and air movement. Adjustments can take into account such things as physical workload, clothing and work organisation.
The Thermal Work Limit (TWL) is an alternative approach being used increasingly in Australian workplaces, particularly in the resource industry. It accounts for all of the major factors mentioned above and provides guidance on managing workloads and fluid intake.
If the assessment indicates a risk of heat illness occurring, employers need to put control measures in place. Workers considered at risk due to factors such as pre-existing medical conditions should be medically assessed.
Where the employer has implemented practical controls, but is not sure whether there is a still a health risk, various forms of risk assessment are available, for example:
Some of these assessments require information such as the Wet Bulb Globe Temperature (WBGT).
This should preferably be measured in the work area, however as a guide, the Bureau of Meteorology provides WBGT values for major centres. An occupational hygienist can assist with such assessments. In some cases (eg when full impermeable suits are worn), direct physiological monitoring of each worker may be required to monitor heat stress.
There is a recommended order of control measures that eliminate or reduce the risks of injury or harm. Often a combination of controls will be necessary. Examples of these are:
Engineering controls are an effective way of reducing heat stress and preventing or minimising occurrence of heat illness. Examples include:
Organisation of work
Heat stress can be reduced by attention to the way work is organised. Examples include:
Providing training and information
Training and information will enable workers to:
Toolbox meetings and pre-start meetings present opportunities to reinforce the actions needed to avoid heat illness.
Providing personal protective clothing
Providing personal protective equipment (PPE) such as reflective aprons and face shields can reduce exposure to radiant heat. Ice vests and liquid and air circulating systems can be worn under PPE where appropriate. Outdoor workers should be provided with protection against ultraviolet exposure, such as a wide brim hat, loose fitting, long sleeved collared shirt and long pants, sunglasses and sunscreen.
Although water is generally adequate for fluid replacement, low joule cordials and electrolyte replacement solutions may be provided to encourage fluid intake. High sugar cordials and sports drinks are not recommended.
Allowing for acclimatisation
Workers, in particular those with fly-in fly-out contracts, may experience significant differences in climatic conditions between the workplace and their off-work location, especially after an extended absence.
Suitable acclimatisation procedures should be considered for workers who are subject to hot work conditions. Such procedures should be developed in consultation with workers and consider the particular shift roster schedules used.
Other preventative measures
Employers should plan ahead and ensure all the necessary measures for preventing heat illness can be implemented when hot weather is predicted.
Have the person rest in the coolest available place and drink cool but not cold fluids. Provide an electrolyte supplement or sports drink if available.
Contact a doctor, nurse, ambulance service or first aid officer if the symptoms do not reduce quickly or if symptoms of heat stroke are present.
Symptoms: fainting, headache, low blood pressure, nausea, clammy, pale or flushed skin, normal to high body temperature (up to 39C).
Symptoms: irritability, confusion, speech problems, hot dry skin, convulsions, unconsciousness, body temperature above 40C, cardiac arrest - potentially fatal, a life threatening condition that requires immediate first aid and medical attention.
If you believe there are problems with heat stress at your workplace you should discuss them with your employer and your safety and health representative.