What is Heat Stress??
Occurs when the body’s total net heat load on the person from internal heat produced & external sources exceeds the body’s ability to cool itself.
Levels of heat stress
Mild heat stress is not harmful, more serious heat stress can cause:
- Heat oedema: swelling
- Heat rashes: tiny red spots on skin, which cause a prickling sensation
- Heat cramps: sharp pains in the muscles
- Heat exhaustion: excessive loss of water & salt
- Heat syncope: fainting
- Heat stroke the most serious form of heat stress
What causes Heat Stress?
- humidity – the moisture content of the air (as humidity increases, the air is less able to absorb moisture from the skin and sweating becomes less effective at cooling the body)
- amount of air movement (indoors) or wind speed (outdoors)
- radiant temperature of surroundings, such as the sun (outdoors) or furnaces, ovens and working under a metal roof (indoors)
- clothing being worn – including personal clothing being worn under protective clothing such as overalls
- type of physical activity being done and the length of time it is done for
- age and physical fitness of the worker
Heat Exhaustion
Is caused by excessive loss of water & salt
Symptoms
- Heavy sweating (eventually may stop)
- Weakness
- Dizziness
- Nausea
- Headache
- Muscle cramps
Heat Stroke
- Elevated body temperature greater than 41°C
- Red hot dry skin
- Rapid strong pulse
- Vomiting
- Confusion
- Dizziness
- Life threatening & requires immediate medical attention
- Can lead to partial or complete loss of consciousness
Who is prone to Heat Stress?
- are overweight
- are physically unfit
- are pregnant
- have consumed drugs or alcohol
- are over 45 years old (research suggests workers over 45 years of age experience a lower ability to work in a hot environment, which can make them a particularly vulnerable group as heat intensifies)
- suffer from heart or lung disease
- take certain medications or are on a fluid-restricted diet
- aren’t used to working in the heat.
First Aid for Heat Stress
Heat-related illness is progressive. If not treated it can be fatal. Certain medications and conditions make you susceptible to heat related illness.
Dehydration
- Mild to severe thirst (remember that thirst is satisfied before fluid loss is fully replaced).
- Dry lips and tongue.
- Slowed mental function & lowered performance.
- Reduced or dark urine output.
Treatment
– Drink water. Avoid caffeinated, carbonated and salt tablets. Loosen tight clothing and remove unnecessary clothing, including PPE. In cases of extreme heat or dehydration, replace electrolytes.
Heat Rash
- Itchy rash with small raised red spots on the face, neck, back, chest or thighs.
Treatment
-Move to a cooler, less humid environment.
-Keep the affected area dry and remove unnecessary clothing, including PPE.
Apply a cold compress.
Heat Cramps
Painful and often incapacitating cramps in muscles, particularly when undertaking demanding physical work.
Treatment
-Stop activity and rest quietly in a cool place until recovered. Drink an electrolyte solution.
Fainting
(heat syncope) can occur while standing or rising from a sitting position.
Treatment
-Lie the worker flat immediately with their legs slightly raised. Do not raise the head. Treat as for heat exhaustion
First Aid for Exhaustion
– Dehydration, thirst, and reduced or dark urine output. Sweating. Elevated body temperature. Weakness or fatigue. Headaches and dizziness. Nausea. Muscle cramps.
Severe symptoms: Clumsiness or slower reaction times. Disorientation or impaired judgement. Rapid or short breathing. Rapid weak pulse or heart palpitations. Tingling or numbness in fingers or toes. Visual disturbance. Vomiting or an unwillingness to drink.
Treatment
Move the worker to a cool place with circulating air. Lie the worker flat. Loosen tight clothing/PPE. If fully conscious sit them up to help to drink and provide cool – not cold – fluid to drink. Provide an electrolyte solution or water. Cool the worker with cold compresses or apply cold water to skin. Observe the worker and obtain medical assistance if symptoms don’t improve.
First Aid for Heat Stroke
-The person stops sweating. Skin can be pink, warm and dry, or cool and blue. High body temp above 39 degrees C. Pounding, rapid pulse. Headache, dizziness, visual disturbances. Nausea and/or vomiting. Clumsiness or slower reaction times. Disorientation or impaired judgement. Collapse, seizures and unconsciousness. Cardiac arrest. Unconsciousness, stopped breathing and no pulse.
Treatment
Call 000. Ensure that the ambulance is updated if the worker experiences seizures or becomes unconscious. Loosen tight clothing. Cool the worker by splashing room temp water on their skin or sponging their skin with a damp cloth. Make a wind tunnel by suspending sheets around, not on, the worker’s body. Use a fan to direct gentle airflow over the worker’s body. Apply cold packs or wrapped ice to the worker’s neck, groin and armpits. If the worker is conscious sit up to facilitate drinking and provide cool fluid to drink. Provide an electrolyte solution with sugar. Do not attempt to give oral fluid if the worker is not fully conscious.
Worker & Supervisor Responsibilities
Employees’ Responsibilities
- know the potentially harmful effects of heat stress & recognise the physical ‘warning signs’
- rehydrate if heat exhaustion starts
- if dizziness occurs rest in shade & rehydrate
- if colleague exhibits heat stress assist with first aid measures
- report incidents to supervisor
Managers and supervisors Responsibilities
- Ensure preventive heat stress measures are implemented, rehydration breaks, shade, air condition environment e.g. car to prevent symptoms escalating
- Monitor workers in heat wave conditions & encourage heat stress to be reported
- Carry out a regular review of workplace procedures & accessibility to first aid supplies
Important Tools –
Prepare if going to be unusually hot by using
- Bom Website Heat Wave Maps of Australia www.bom.gov.au/australia/heatwave/
- Working out the daily Heat Index using predicted Temp & Humidity = Actual Temp to body
- Body core Temp also is elevated by clothing & degree of exercise being completed by worker
Body Core Temp
- NIOSH recommends the core body temperature does not exceed 38°C.
- Workload raises body core temp e.g. heavy lifting or landscaping tasks will increase workload.
- Heavy work load can burn 600 kcal/hr for 70kg male for 100kg male increases to 860 kcal/hr
- If body reaches 40 °C can induce severe heat stress reactions such as heat stroke
- Important to check body temperature & if at 38 °C rest & rehydrate
Acclimatising Staff
Acclimatisation starts by constant heat exposure the body reacts by small physiological adaptation to help employee cope better to the heat stress.
This response will happen after constant heat exposure for a period of 2 hours, and tolerance is lost when the heat exposure is discontinued after a period of 4 days and completely lost after 3 weeks.
Heat Stress Preventatives
steps to consider for hot conditions
- Use of mechanical aids (tractors, forklifts, mechanical lifters).
- Use shade where possible, at least for rest periods.
- Supervisors monitor temp, humidity and workers’ physical response to the heat.
- Have frequent rest breaks and/or rotate duties to allow people to cool down.
- Schedule heavy work and tasks that require the wearing of PPE for cooler times of day
- A useful “rule of thumb” is that workers should drink at least half a litre of water each hour if hot environments result in excessive sweating.
- Use fresh water supply for washing and external cooling eg. wet towels.
- Use cooling vests & cool packs