For workers in many industries, hot, humid and hard-working conditions are a fact of life. Construction, utility and agriculture workers regularly toil outside in hot, humid weather. Employees in manufacturing plants, metal processing facilities and foundries also face severe heat from these indoor operations. Workers who must wear heavy, protective apparel on the job feel the heat no matter what the weather.

Industry estimates place the number of workers for whom heat stress is a potential safety and health hazard at 5 million to 10 million. For these workers and others, access to clean drinking water is a serious issue -- one that affects their health and productivity.

Without easy access to fluids, workers can become dehydrated, which is a prime cause of heat illness. In addition to the health benefits of proper hydration, workers who hydrate correctly are more comfortable, cool and alert -- making for a more productive and healthier work force.

How the Body Handles Heat

The human body maintains a fairly constant internal temperature, even when exposed to varying environmental temperatures. To get rid of excess heat, the body varies the rate and amount of blood circulation through the skin and the release of fluid onto the skin by the sweat glands.

As environmental temperatures approach normal skin temperature, cooling of the body becomes more difficult as blood brought to the body surface cannot lose its heat.

At that point, sweat evaporation becomes the principal means to maintain a constant body temperature.

Sweating does not cool the body, however, unless the moisture is removed from the skin by evaporation, which is difficult under conditions of high humidity or when wearing heavy protective clothing. Moreover, profuse and prolonged sweating can also disturb normal cardiovascular functions, according to the American Conference of Governmental Industrial Hygienists (ACGIH).

Excessive exposure to a hot work environment can bring about a variety of heat-induced disorders. In fact, after just two hours of moderate work, workers may begin to feel the initial stages of heat stress. After another hour, they may start to lose strength, energy and focus. At its most severe point, heat stress can result in collapse or unconsciousness.

The human body requires fluid to control temperature and maintain muscle function. In hot, hard-working conditions, workers can lose up to 1.5 liters of water each hour in the form of sweat. Plus, sweat-laden skin and clothing reduce heat dissipation normally performed by the body.

How to Hydrate

Replacing body fluids lost during sweating, therefore, is the single most important way to control heat stress and keep workers comfortable, productive, alert and safe. In fact, physiological studies have shown that fluid ingestion reduces the rise in body temperature by promoting higher skin blood flow. The greatest rates of skin blood flow occurred in these studies when the largest volumes of fluid were ingested during physical activity.

The National Institute for Occupational Safety and Health (NIOSH) recommends fluid replacement not only as treatment for heat exhaustion, but as a preventive measure (i.e., water intake equal to the amount of sweat produced). The Occupational Safety and Health Administration (OSHA) identifies fluid replacement (drinking water) as one of its top 10 tips for staying cool in hot workplaces. ACGIH also calls for similar water intake for workers in hot conditions.

Hydration experts from NIOSH, ACGIH and OSHA recommend drinking every 15 to 20 minutes -- not just during rest breaks -- to stay sufficiently hydrated and maintain a safe core body temperature. This puts less strain on the cardiovascular system and can lead to fewer heat-related illnesses and injuries.

Other tips for keeping workers hydrated and healthy :

  • Drink before, during and after physical labor to replace body fluid lost in sweating.
  • Anticipate conditions that will increase the need for water, including high temperature, humidity, protective clothing and difficulty of work.
  • Keep in mind that by the time you are thirsty, you are already about 2 percent dehydrated. Once you are dehydrated, it's difficult to make up for that lost hydration.
  • Drink 5 to 7 ounces of fluids every 15 to 20 minutes to ensure proper hydration.
  • Keep individual containers of cool, clean water within easy reach at all times. NIOSH recommends prohibiting communal drinking containers in workplace settings, and ACGIH recommends placing water close enough to workers so they can reach it without abandoning the work area.
  • Drink cool water, which is absorbed more quickly by the body than warm or very cold fluids. NIOSH and ACGIH recommend drinking water of 50 to 59 degrees.
  • Try carbohydrate/electrolyte drinks to help avoid heat cramps that can occur up to several hours after working.
  • Avoid coffee, tea or soda, which act as diuretics, further depleting the body of fluid. Never drink alcohol while working.
  • Even sedentary workers should drink eight 8-ounce servings of water every day.

When workers are properly hydrated, they are healthier, safer and more productive, no matter what the weather or working conditions.

Gavin McLachlan is director of CamelBak Products' Industrial Safety Division in Petaluma, Calif. CamelBak offers a full range of hands-free hydration systems to workers in a variety of industries exposed to hot, humid and hard-working conditions.