Heat Stress is a major PDO and Contractor H&S hazard. Analysis of the Lost Time Injury (LTI) statistics shows that incidents and injuries increase leading up to and during the summer period and decline during the cooler months. During summer months, the ambient temperature in the interior can exceed 50°C and the relative humidity in coastal areas regularly exceeds 70% from June to September.
It is important for all supervisors to consider this hazard when preparing for work involving outdoor tasks, radiant sources (machinery) and the fitness and acclimatisation of the workforce.
Understanding Heat Stress
Heat stress occurs when heat is absorbed from the environment faster than the body can get rid of it. Several factors may contribute to heat stress, such as the type of work activity, the surrounding air temperature/humidity level, and the physical condition of the individual (he may be new to the job or new to Oman). Our bodies maintain a fairly constant internal temperature even though they may be exposed to varying environmental temperatures. To keep internal body temperatures within safe limits in hot conditions, the body has to get rid of excess heat – and it does this by evaporating sweat and varying the blood flow to the skin. These responses are controlled by the brain and usually occur when the blood exceeds 37°C. Factors that may contribute to heat-related health problems at work include:
- inadequate cooling off or rest periods
- insufficient water consumption
- climatic conditions (such as low air movement, high humidity levels and high air temperature)
- inappropriate clothing (synthetic material)
- individual factors that may cause dehydration (such as poor diet, vomiting, diarrhoea or alcohol and caffeine consumption)
- individual medical conditions that may cause heat stress (such as heart problems, diabetes or hypertension)
- individual medication that may affect the body’s temperature regulation
- an individual’s age, general physical fitness and weight
Environment and seasonal factors that can contribute to heat problems:
- high air temperatures
- radiant heat from hot objects such as machinery
- radiant heat from working outdoors in the sun
- higher relative humidity levels
- low air movement
Various engineering controls are effective for reducing heat in workplaces. Examples include:
- reducing the body’s metabolic heat production using automation and mechanisation of tasks
- reducing radiant heat emissions from hot surfaces and plant e.g. by insulation and shielding
- using ventilation and air-conditioning
- humidity reducing methods e.g. install a dehumidifier (seek engineering advice)
- creating some shade (tarp, umbrella) or at least find a tree for outdoor workers’ during rest breaks.
Types of Heat Related Illnesses
Over the last couple of weeks we have seen an increase in the number of heat exhaustion cases reported. Normal controls to reduce this risk include providing cool water, shade and regular rest periods. In addition staff need to be aware of the symptoms and first aiders trained in dealing with such cases.
Heat exhaustion develops over hours or days due to water and electrolyte loss from sweating. Symptoms are headaches, dizziness, fatigue, nausea and vomiting. Physically the pulse will be rapid, the skin will be moist and the person may be pale.
Treatment: The key issue is fluid loss, have the patient drink water (1/4 teaspoon of salt in a litre of water helps replace salts). Provide shade and cool the patient.
Heatstroke results in sudden collapse with extreme rise in the body temperature, decreased mental ability and shock. It is a medical emergency that can kill. Symptoms are headaches, drowsiness, irritability, confusion sometimes with convulsions. Its onset can be very sudden. Physically the person will be hot with a bounding pulse.
Treatment: Remove the patient from the heat, and cool rapidly, this can be done by putting them in a cold bath or soak them and fan rapidly. Cool packs (not ice) can be placed near the neck, the stomach, armpits and groin. You must monitor their temperature and stop cooling when they reach 39ºC. Continue to monitor the temperature so it does not go higher or lower. The person must be sent to hospital urgently.
Cramping that occurs during exercise or with heat exhaustion. Like heat exhaustion it is caused by salt and water depletion.
Treatment: Stretch the affected muscles, provide weak solution of salt water (see above). Do not give salt tablet.