Heat Stress and Heat Stroke

According to the reports of global climate risk, India is classified under the most vulnerable regions exposed to extreme weather conditions with resulting huge economic loss due to heat induced decreased health, work capacity, productivity consequences, fatalities Heat Stress and Heat Stroke. In particular, the southern region is most influenced by climatic fluctuations, has high-heat conditions for the most part of the year that largely influences the indoor workplace temperatures further worsened by heat generated from the processes with consequent undesirable health and productivity.
Several studies have identified heat stress as an important health risk in agricultural and industrial sectors in India. The major industries studied so far include automotive, coal mines, ceramics and pottery, iron works, stone quarry and textiles.
Many workers spend some part of their working day in a hot environment, which poses special hazard to safety and health. This hazard is known as heat stress, which occurs when heat is absorbed from the environment faster than the body can get rid of it.
Heat stress occurs when the body cannot get rid of excess heat. When this happens, the body’s core temperature rises and the heart rate increases. As the body continues to store heat, the person begins to lose concentration and has difficulty focusing on a task, may become irritable or sick, and often loses the desire to drink. The next stage is most often fainting and even death if the person is not cooled down.
Factors that contribute to heat stress are high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, and strenuous physical activities.

Some following example given below about heat stress:

  • Someone wearing protective clothing and performing heavy work in hot and humid conditions could be at risk of heat stress because:
  • Sweat evaporation is restricted by the type of clothing and the humidity of the environment
  • Heat will be produced within the body due to the work rate and, if insufficient heat is lost, core body temperature will rise
  • As core body temperature rises the body reacts by increasing the amount of sweat produced, which may lead to dehydration.
  • Heart rate also increases which puts additional strain on the body.
  • If the body is gaining more heat than it can lose the deep body temperature will continue to rise eventually it reaches a point when the body’s control mechanism itself starts to fail.

Where does heat stress occur?

Examples of workplaces where people might suffer from heat stress because of the hot environment created by the process, or restricted spaces are:

  • Glass and rubber manufacturing plants
  • Mines
  • Compressed air tunnels
  • Conventional and nuclear power plants
  • Foundries and smelting operations
  • Brick-firing and ceramics plants
  • Boiler rooms
  • Bakeries and catering kitchens
  • Laundries

In these industries working in the heat may be the norm. For others it will be encountered more irregularly depending on the type of work being done and changes in the working environment, eg seasonal changes in outside air temperature can be a significant contributor to heat stress.

Signs, Symptoms of heat illness

Working in very hot areas, our bodies get rid of excess heat by sweating, increasing blood circulation and increasing the blood flow to the skin. When this works well, the body temperature drops or stabilizes at a safe level. However, if the body cannot cool off quickly, various forms of heat illness can develop.
The four major heat illnesses are:

  • Heat Rash
  • Heat Cramps
  • Heat Exhaustion
  • Heat Stroke

Heat Rash (Prickly Heat)

Heat Rash is a common condition in which areas of the skin itch intensely and often feel prickly, or sting due to overheating. Heat Rash looks like tiny bumps surrounded by a zone of red skin.


  • Sweat ducts become plugged, rash develops, skin remains wet because sweat does not evaporate readily.
  • Treatment and Prevention
  • Move to a cooler, less humid place.
  • Don’t scratch your skin, or it could become infected.
  • Keep the affected area dry.
  • Don’t use ointments or creams that keep your skin moist.
  • You can put powder on the rash to feel more comfortable.
  • Use a fan.
  • Wear clothes that aren’t tight and don’t trap heat and moisture.

Heat Cramps

Heat cramps are muscular spasms that occur when the body loses too much salt during profuse sweating.


  • Painful
  • Involuntary
  • Brief
  • Intermittent
  • Usually self-limited (go away on their own)
  • Shriveled skin, sunken eyes, dry mouth and tongue
  • Severe pain and cramps in legs and abdomen, fainting or dizziness, weakness, profuse sweating, and headaches

Treatment and Prevention

  • Stop the activity being performed,
  • Get to a cooler place,
  • Drink plenty of fluids, and
  • Gently stretch the muscles that are cramping.

Heat Exhaustion

It is a heat-related illness that can occur after you’ve been exposed to high temperatures, and it often is accompanied by dehydration. There are two types of heat exhaustion:

  • Water depletion.
  • Salt depletion.


The most common signs and symptoms of heat exhaustion include:

  • Confusion
  • Dark-colored urine (a sign of dehydration)
  • Dizziness
  • Fainting
  • Fatigue
  • Headache
  • Muscle or abdominal cramps
  • Nausea, vomiting, or diarrhea
  • Pale skin
  • Profuse sweating
  • Rapid heartbeat

Treatment for Heat Exhaustion

  • Drink plenty of fluids, especially sports drinks to replace lost salt (avoid caffeine and alcohol).
  • Remove any tight or unnecessary clothing.
  • Take a cool shower, bath, or sponge bath.
  • Apply other cooling measures such as fans or ice towels.

Heat Stroke

Heat stroke is the most serious heat-related illness. It occurs when the body becomes unable to control its temperature: the body’s temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. When heat stroke occurs, the body temperature can rise to 106°F or higher within 10 to 15 minutes. Heat stroke can cause death or permanent disability if emergency treatment is not given.

Symptoms of Heat Stroke

  • Confusion, altered mental status, slurred speech
  • Loss of consciousness (coma)
  • Hot, dry skin or profuse sweating
  • Seizures
  • Very high body temperature
  • Fatal if treatment delayed
  • Warning signs of heatstroke vary, but may include:
  • Red, hot, dry skin (no sweating)
  • Dry swollen tongue
  • Rapid pulse
  • Throbbing headache
  • Dizziness, confusion, nausea
  • Collapse
  • Eventual unconsciousness.

Treatment of heat stroke

  • Immerse you in cold water
  • Use evaporation cooling techniques
  • Pack you with ice and cooling blankets
  • Give you medications to stop your shivering
  • Eat smaller meals more often and cold meals such as salad.
  • Wear light-colored, loose-fitting clothing made from natural fibers like cotton and linen.

Control and prevention of heat stress

Employees should take special precautions to avoid heat-related illness in unusually hot weather when working outdoors or in unconditioned indoor environments. People suffer heat-related illness when their bodies are unable to regulate internal body temperature. In hot weather, the body normally cools itself by sweating. Under some conditions, however, sweating isn’t enough. Such conditions include high humidity, where air movement is limited, working in the direct sun, heavy physical exertion and poor physical condition. Some medical conditions and medications can also reduce the body’s ability to tolerate heat. Still, heat-related illness is preventable by following these guidelines when working outdoors in hot weather:

Engineering Controls

The best engineering controls to prevent heat-related illness is to make the work environment cooler and to reduce manual workload with mechanization. A variety of engineering controls can reduce workers’ exposure to heat:

  • Air conditioning (such as air-conditioned crane or construction equipment cabs, air conditioning in break rooms)
  • Increased general ventilation
  • Cooling fans
  • Local exhaust ventilation at points of high heat production or moisture (such as exhaust hoods in laundry rooms)
  • Reflective shields to redirect radiant heat
  • Insulation of hot surfaces (such as furnace walls)
  • Elimination of steam leaks
  • Cooled seats or benches for rest breaks
  • Use of mechanical equipment to reduce manual work (such as conveyors and forklifts).
  • Misting fans that produce a spray of fine water droplets

Work Practices

Some worksites cannot be cooled by engineering controls. At those locations, employers should modify work practices when heat stress is too high to work safely. Consider the following activity modifications (also known as “administrative controls”):

  • Modify work schedules and activities for workers who are new to warm environments.
  • Schedule shorter shifts for newly hired workers and unacclimated existing workers. Gradually increase shift length over the first 1-2 weeks.
  • Require mandatory rest breaks in a cooler environment (such as a shady location or an air conditioned building). The duration of the rest breaks should increase as heat stress rises.
  • Consider scheduling work at a cooler time of day, such as early morning or late afternoon.
  • Reduce physical demands as much as possible by planning the work to minimize manual effort (such as delivering material to the point of use so that manual handling is minimized).
  • Rotate job functions among workers to help minimize exertion and heat exposure.
  • Ensure that workers drink an adequate amount of water or electrolyte-containing fluids.
  • Employers should have an emergency plan that specifies what to do if a worker has signs of heat-related illness, and ensures that medical services are available if needed.
  • Workers should watch out for each other for symptoms of heat-related illness prepared to administer appropriate first aid to anyone who is developing a heat-related illness.
  • Administer appropriate first aid [hyperlink to first aid page] to any worker who is developing a heat-related illness.
  • In some situations, employers may need to conduct physiological monitoring of workers.
  • Implement a buddy system for new workers and in heat stress environments.
  • Avoid drinking hot beverages during lunch and afternoon breaks.

Personal Protective Equipment

In most cases, heat stress should be reduced by engineering controls or work practice modifications. However, in some limited situations, special cooling devices can protect workers in hot environments:

  • Insulated suits
  • Reflective clothing
  • Infrared reflecting face shields
  • Cooling neck wraps

In extremely hot conditions, the following thermally conditioned clothing might be used:

  • Vest that receives cooled air from a vortex tube connected to an external compressed air source.
  • Jackets or vests with reusable ice packs or phase change cooling packs in the pockets.
  • Workers should be aware that use of certain personal protective equipment (e.g., certain types of respirators, impermeable clothing, and head coverings) can increase the risk of heat-related illness.


Train workers before hot outdoor work begins. Tailor training to cover worksite-specific conditions.
Employers should provide a heat stress training program for all workers and supervisors about the following:

  • Recognition of the signs and symptoms of heat-related illnesses and administra­tion of first aid.
  • Causes of heat-related illnesses and the procedures that will mini­mize the risk, such as drinking enough water and monitoring the color and amount of urine output.
  • Proper care and use of heat-protective clothing and equipment and the added heat load caused by exertion, clothing, and per­sonal protective equipment.
  • Effects of no occupational factors (drugs, alcohol, obesity, etc.) on tolerance to occupational heat stress.
  • The importance of acclimatization.
  • The importance of immediately reporting to the supervisor any symptoms or signs of heat-related illness in themselves or in coworkers.
  • Procedures for responding to symptoms of possible heat-related illness and for contacting emergency medical ser­vices.

The impact on human function and health in work situations is a ‘neglected’ effect of global climate change. The potential health risks and worker productivity reductions due to climate change are substantial. The lack of attention until recently may well be due to the fact that this is mostly a problem in low and middle-income tropical countries where climate change impacts during this century will be prominent and air conditioning is not widely available, while in high-income countries air conditioning is already very common in workplaces.

The increasing heat exposure due to local climate changes is likely to create occupational health risks and to have a significant impact on the productivity of many workers, unless effective preventive measures (‘adaptation’) reducing the occupational heat stress are implemented. This may be practically and economically possible for indoor environments, but it is much more difficult for outdoor environments. Eventually, this will hamper economic and social development in affected countries unless appropriate preventive measures are taken in the planning processes for workplaces and urban development.

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