Workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational illnesses and injuries. Heat stress can result in heat stroke, heat exhaustion, heat cramps, or heat rashes. Heat can also increase the risk of injuries in workers as it may result in sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam.

Heat stress occurs when your body gets heated up and cannot cool itself down.  It can be a variety of different symptoms ranging from a rash to heat stroke.  It is important to stay hydrated in hot places, including indoors or out in the sun.  Any time the body's deep core temperature is raised, heat stress can occur.  Factors such as body weight, dehydration, metabolism, certain medications or alcohol use can also add to heat stress, causing the heart to work harder and the muscles to lose hydration.

How can you recognize heat stress?

Symptoms include hot skin but no sweat due to dehydration, shakes, chills, severe headache, confusion, dizziness, nausea or a combination of any of these.  Look for red rashes, sore muscles (the person rubbing calves or forearms), dry mouth and general exhaustion.  If a person does not make sense he will need immediate attention because his cognitive thought process is not working under heat stress.

How can you treat heat stress?

• Be sure to make the person sit or lay down on the ground to avoid passing out and injuring the head.
• Get a cool paper or cloth towel for the neck, use cooling products on hand, wet down the clothes
• Put the person in air conditioning or near a fan when possible, and get the person plenty of water.
• Call the emergency responders   Keep an eye on the person while you wait for help.
• Try to keep work limited to short periods of time if you work in a hot environment.
• Give short breaks for staying hydrated
• Get the items like cooling vests, cooling towels or cooling hats wet and applied to hot skin before returning to work.  Cooling kits are available too; add some to your protective equipment
• Do not drink caffeinated beverages in the heat as it causes dehydration.
• Keeping track of your hydration levels and resting whenever possible will be the best way to avoid heat stress.
• Workers in such jobs as construction, landscaping, athletics, warehouses and  fish mongers all have a high risk of heat stress.

Control of Heat Stress

Employers should reduce workplace heat stress by implementing engineering and work practice controls.

Engineering controls might include those that:

• Increase air velocity.
• Use reflective or heat-absorbing shielding or barriers.
• Reduce steam leaks, wet floors, or humidity.

Work practice recommendations include the following:

• Limit time in the heat and/or increase recovery time spent in a cool environment.
• Reduce the metabolic demands of the job.
• Use special tools (i.e., tools intended to minimize manual strain).
• Increase the number of workers per task.
• Train supervisors and workers about heat stress.
• Implement a buddy system where workers observe each other for signs of heat intolerance.
• Require workers to conduct self-monitoring and create a work group (i.e., workers, a qualified healthcare provider, and a safety manager) to make decisions on self-monitoring options and standard operating procedures.
• Provide adequate amounts of cool, potable water near the work area and encourage workers to drink frequently.
• Implement a heat alert program whenever the weather service forecasts that a heat wave is likely to occur.
• Institute a heat acclimatization plan and increase physical fitness.

Training

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 non-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.

In addition, supervisors should be trained on the following:

• How to implement appropriate acclimatization.
• What procedures to follow when a worker has symptoms consistent with heat-related illness, including emergency response procedures.
• How to monitor weather reports.
• How to respond to hot weather advisories.
• How to monitor and encourage adequate fluid intake and rest breaks.

Acclimatization

Acclimatization is the result of beneficial physiological adaptations (e.g., increased sweating efficiency, etc.) that occur after gradual increased exposure to a hot environment. Employers should ensure that workers are acclimatized before they work in a hot environment.

• Gradually increase workers’ time in hot conditions over 7 to 14 days.
• For new workers:

• The schedule should be no more than 20% of the usual duration of work in the heat on day 1 and no more than 20% increase on each additional day.

 

• For workers with previous experience:

 

• The schedule should be no more than 50% of the usual duration of work in the heat on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.

 

• Closely supervise new employees for the first 14 days or until they are fully acclimatized.
• Non-physically fit workers require more time to fully acclimatize.
• Acclimatization can be maintained for a few days of non-heat exposure.
• Taking breaks in air conditioning will not affect acclimatization.

 

Hydration

Employers should provide the means for appropriate hydration of workers.

• Water should be potable, <15°C (59°F), and made accessible near the work area.
• Estimate how much water will be needed and decide who will obtain and check on water supplies.
• Individual, not communal, drinking cups should be provided.
• Encourage workers to hydrate themselves.

Workers should drink an appropriate amount to stay hydrated.

• If in the heat <2 hours and involved in moderate work activities, drink 1 cup (8 oz.) of water every 15–20 minutes.
• During prolonged sweating lasting several hours, drink sports drinks containing balanced electrolytes.
• Avoid alcohol and drinks with high caffeine or sugar.
• Generally, fluid intake should not exceed 6 cups per hour.

Rest Breaks

Employers should ensure and encourage workers to take appropriate rest breaks to cool down and hydrate.

• Permit rest and water breaks when a worker feels heat discomfort.
• Modify work/rest periods to give the body a chance to get rid of excess heat.
• Assign new and unacclimatized workers lighter work and longer, more frequent rest periods.
• Shorten work periods and increase rest periods:

• As temperature, humidity, and sunshine increase.
• When there is no air movement.
• If protective clothing or equipment is worn.
• For heavier work.

The Wet Bulb Globe Temperature or WBGT index was measured using a digital WBGT meter on areas where workers are subjected to hot environment. Threshold limit values (TLV) and Screening Action Limits (AL) are based on ACGIH (American Conference of Governmental Industrial Hygienists) Heat Stress Criteria of 2017, given below.

MANUAL COMPUTATION OF HEATSTRESS :

The heat stress formula referenced by the U.S. Government Occupational and Environmental Health Bulletin is:

WBGT (outdoor) = 0.7 x WB + 0.2 x BG + 0.1 x DB WBGT (indoor) = 0.7 x WB + 0.3 x BG

Where:

• WB is the wet-bulb temperature
• BG is the 6-inch Vernon Black Globe temperature
• DB is the dry-bulb (ambient) temperature
• WBGT is the wet-bulb globe temperature index

Heatstress Recommendation

The following are the recommended general corrective measures when the results of measurement failed to meet the threshold limit value, whichever is applicable:

Engineering Control

1. Modification or Isolation of the process
2. Provide reflective shields between the heat source and the worker
3. Provision of heat insulation or heat barrier
4. Installation of spot cooling device

Administrative Control

1. Provision of cold drinking water near the area
2. Reduction of working hours of exposed workers
3. Use of control room
4. Safety and health orientation
5. Posting of warning signs and safety reminders

Use of PPE

Use of personal protective equipment such as heat resistance protective clothing

 

 

 

References:

https://www.equipcoservices.com/support/tutorials/introduction-to-heat-stress-monitors/

National Institute for Occupational Safety and Health (NIOSH)

American Conference for Governmental Industrial Hygienist