When the Mercury Soars

Employers should use common sense when determining workers' fitness for work in hot environments, OSHA advises.

SUMMER brings us long days and a great deal of work outdoors for many Americans, from farm laborers and loggers to road and highway construction crew members. The hottest season of the year also naturally reminds us of heat stress hazards. But the great outdoors isn't the only "hot" zone to monitor, just the most obvious one. Foundries, factories, welding shops, construction sites, commercial kitchens, airports, laundries, chemical plants, mines, stadiums, and many other locales are danger zones for occupational heat stress, as well.

As is the case with virtually all other safety hazards, the best defense for heat stress is establishing and enforcing proper procedures with all employees who are exposed.

OSHA routinely issues summertime advisories to warn workers and their employers about heat hazards. "Some simple adjustments during these hot summer months can prevent needless tragedy," OSHA's Charles Jeffress said in 1999. "The risk of heat-related illnesses can be reduced by drinking plenty of water, taking frequent rest breaks, wearing appropriate clothing and having access to shaded, well ventilated areas."

Some people are more susceptible to heat stress than others, so OSHA cautions employers to know the symptoms and take quick action when they occur. The agency's 10 tips for workers and employers are:

1. Drink cool water. Anyone working in a hot environment should drink cool water in small amounts frequently--one cup every 20 minutes. Employers should make water available. Avoid alcohol, coffee, tea, and caffeinated soft drinks, which cause dehydration.

2. Dress appropriately. Wear lightweight, light-colored, loose-fitting clothing and change clothing if it gets completely saturated. Use sunscreen and wear a hat when working outdoors. Avoid getting sunburn.

3. Work in ventilated areas. All workplaces should have good general ventilation, as well as spot cooling in work areas of high heat production. Good air flow increases evaporation of sweat, which cools the skin.

4. Work less, rest more. Supervisors should assign a lighter workload and longer rest periods during days of intense heat. Short, frequent work-rest cycles are best. Alternate work and rest periods with longer rest periods in a cooler area, and schedule heavy work for cooler parts of the day.

5. Ask workers how they're feeling. Supervisors should monitor workplace temperature and humidity and check workers' responses to heat at least hourly. Allow a large margin of safety for workers. Be alert to early signs of heat-related illness and allow workers to stop their work for a rest break if they become extremely uncomfortable.

6. Know the signs and take prompt action. Employees and employers should learn to spot the signs of heat stroke, which can be fatal. Get emergency medical attention immediately if someone has one or more of the following symptoms: mental confusion or loss of consciousness, flushed face, hot, dry skin, or has stopped sweating.

7. Train first aid workers. First aid workers should be able to recognize and treat the signs of heat stress. First aid workers should also be able to recognize the signs and symptoms of heat exhaustion, heat cramps, and other heat-related illness. Be sure that all workers know who is trained to give first aid.

8. Reduce work for anyone at risk. Employers should use common sense when determining fitness for work in hot environments. Lack of acclimatization, age, obesity, poor conditioning, pregnancy, inadequate rest, previous heat injuries, certain medical conditions and medications are some factors that increase susceptibility to heat stress.

9. Check with your doctor. Certain medical conditions, such as heart conditions and diabetes, and some medications can increase the risk of injury from heat exposure. Employees with medical conditions or taking medications should ask their doctors before working in hot environments.

10. Watch out for other hazards. Use common sense and monitor other environmental hazards that often accompany hot weather, such as smog and ozone.

Promoting Awareness
Sweat can drain a worker's body of up to 6 quarts of water in one day, the equivalent of about 13 pounds. Replacing this fluid can be accomplished by drinking water or electrolyte-replacing drinks in small quantities, as frequently as possible throughout the day. And while supervisors and employees must be able to recognize symptoms and signs of heat stress, it is equally important to remove the affected individual to a cooler environment immediately. Managers must be able and willing to terminate a situation with the potential for heat stress--regardless of deadlines or work schedules.

The worker's environment, activity level, clothing, and hydration are important factors for preventing heat stress. Someone suffering from heat stress experiences higher body temperature, faster heart rate, and excessive sweating. An increased metabolism means an increase in body core temperature--one of the major concerns for workers in high-heat environments. Because heat exchange with the environment occurs on the skin, blood circulating through the body is sent to the skin, where the blood is cooled before returning to be rewarmed at the core.

The individual's heart rate reveals what is going on inside an overheated body. The total blood through the heart is proportional to the metabolic rate and inversely proportional to the temperature difference between the body core and the skin. According to Fundamentals of Industrial Hygiene, "as work demands and metabolic rate increase, cardiac output increases, as seen in the heart rate." The greater the heat stress, the greater the rate and volume of sweat. But in extreme cases of heat stroke, the skin is hot and dry.

Assessing the site or workplace for heat stress risks involves answering these questions:

  • Is the environment hot or uncomfortable?
  • Are the work demands high?
  • Would cooling apparel decrease the risks of heat stress among the workforce?
  • How is workers' morale? Are they behaving safely and rationally?
  • Do workers have a history of fatigue, weakness, rashes, headaches, or high body temperature in or around the site?
  • Is the average worker suffering from high body temperature, high heart rate, or abnormal sweat loss?
  • Are adequate supplies of water and/or electrolyte-replacing drinks made available throughout the work day?
  • Are these supplies personalized rather than communal?
  • Are rest breaks called frequently--and more often as the ambient heat rises?

Training and Prevention
Training is one of the best tools for managing heat stress. Train all employees, not just those who are in high-heat environments. Evaluate PPE and engineering controls that can cool the workers, including personal cooling systems, cooling vests, ventilation systems, supplied air respirators.

By knowing the variables that contribute to heat stress, you should be able to anticipate the worst before it happens. Choosing the right apparel, being able to recognize heat stress symptoms and potential danger zones, and knowing how heat stress happens are your best tools for keeping everyone cool and healthy.

This article originally appeared in the July 2003 issue of Occupational Health & Safety.

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