Keeping Workers Hydrated and Cool Despite the Heat

Posted on by Brenda Jacklitsch, MS
worker with glaring sun to his backMany areas of the country have been experiencing extreme temperatures this summer, and sadly the news has been full of stories about the lives lost due to heat stroke. While newscasters warn to stay out of the heat, many workers do not have that option. Keeping workers cool and well-hydrated are the best ways to protect them when working in hot environments.

Risk factors for heat illness

Workers should be made aware of the many risk factors that may affect their heat tolerance. Risk factors that may influence heat illness include high air temperatures and humidity, direct sun exposure, indoor radiant heat sources (ovens, hot manufacturing processes, etc.), limited air movement, physical exertion, not drinking enough fluids (dehydration), personal protective equipment or clothing, certain medications, physical condition, lack of recent exposure (not acclimatized), and advanced age (65+). Workers should discuss their individual risk factors with their healthcare provider.

Staying hydrated

The average person has 2.6 million sweat glands. These glands are activated when a portion of the brain determines that the body needs to be cooled down. Sweat evaporates off our skin which allows for heat loss and cooling. However, when we sweat, we also lose water and electrolytes (i.e., “salts” such as sodium, chloride, potassium). Drinking enough water and having enough electrolytes is necessary for our bodies to function properly. This is why it is so important to stay hydrated; a dehydrated person is likely to start having symptoms of heat illness.

NIOSH recommends that for moderate activity in moderate conditions, each worker should drink 1 cup of water every 15 to 20 minutes. Workers should be reminded to drink water frequently before becoming thirsty in order to maintain good hydration. While some workers may prefer the taste of sports drinks, often these types of drinks are not necessary for electrolyte replacement. Workers that eat regular meals and salt-containing snacks will usually be able to replace electrolytes lost during sweating.

In addition to providing plenty of water in convenient locations close to the work site, employers can provide urine color charts near toilet facilities. These charts show the urine colors of a hydrated person compared to a dehydrated person. The darker the urine, the more likely your body is dehydrated.

Keeping cool

Even when the body is at rest, we are internally producing heat through metabolism (breaking down the food we eat into energy). However, during physical exertion, working muscle produces heat at a much higher, faster rate. This increased heat production can result in an increase in body temperature, which above a certain temperature, can be difficult to control. Therefore, it is important to develop ways to cool down the body to help maintain core temperature and reduce the negative effects of thermal stress.

Workers should be allowed to take regular rest breaks. Breaks should be held in a shaded or air conditioned area. Employers and supervisors should be monitoring weather reports daily, and if possible, jobs with high heat exposure should be rescheduled to cooler times of the day. The use of reflective clothing, water-dampened cotton clothing (although this may not work when the humidity is very high), and cooling vests with pockets for cold packs may also be beneficial for keeping workers not only cooler for longer periods of time, but also safer.

Myths about heat stress

There are many misconceptions about heat stress, heat illnesses, and what a person should do when they are required to work hard in a hot environment. The following examples are a few of the myths and common misunderstandings about heat stress and heat illnesses.

MYTH: The difference between heat exhaustion and heat stroke is there is no sweating with heat stroke.

Exertional heat stroke victims may continue to produce sweat [Dept. of the Army and Air Force Technical Bulletin 2003; Armstrong et al. 2007; Navy Environmental Health center 2007]. If a worker is experiencing symptoms of heat stroke (confusion, loss of consciousness, seizures, high body temperature), whether they are sweating or not, it is a life-threatening emergency! Call 911 and try to cool the worker down.

MYTH: Taking a break in the air conditioning will ruin your acclimatization.

Acclimatization can usually be maintained for a few days of non-heat exposure, so taking a break in the air conditioning will not reduce a worker’s level of acclimatization. And it is a very effective way for workers to cool down in a fairly short period of time.

MYTH: Acclimatization will protect you during a heat wave.

Acclimatization occurs when a person is exposed to extreme environmental conditions over a 7-10 day period. However, during heat waves air temperatures rise above normal quickly, and workers will not be able to immediately acclimatize to the new, hotter temperatures. During heat waves, workers will need more breaks and rescheduling some of the harder and hotter job tasks may be warranted.

MYTH: Salt tablets are a great way to restore electrolytes lost during sweating.

Salt tablets should never be used unless a worker is instructed to do so by their doctor. Most people are able to restore electrolytes through normal meals and snacks. Workers should drink plenty of water with their meals and snacks, not only to stay hydrated but also to aid digestion. Moreover, ingestion of too much salt may cause nausea and vomiting which can worsen the level dehydration already present.

MYTH: My medications/health condition will not affect my ability to work safely in the heat.

A worker’s health and medication usage may affect how their body handles high temperatures and heavy physical exertion. Some health problems that may put a worker at a greater heat illness risk include: obesity, diabetes, cardiovascular disease, and even common colds and the flu—especially if the illness is accompanied by a fever and vomiting. Certain medications may affect the body’s ability to cool down or may cause the body to heat up more quickly. Examples of medications that increase risk are diuretics, antihypertensives, and anticholinergics. Workers with health conditions or who are taking medications should discuss with their physicians about how they may be at additional risk if working in a hot environment.

NIOSH heat illness resources

NIOSH is working with the Occupational Safety and Health Administration (OSHA) and other partners to provide heat illness information for employers and workers. Please share with us how you stay cool on the job. For additional information on heat stress, heat illnesses, and hot environments see:

Ms. Jacklitsch is a biologist and epidemiologist with NIOSH’s Document Development Branch.


  1. Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO [2007]. American College of Sports Medicine position stand. Exertional heat illness during training and competition. Med Sci Sports Exerc 39(3): 556-572.
  2. Navy Environmental Health Center (2007). Prevention and Treatment of Heat and Cold Stress Injuries. Vol Technical Manual NEHC-TM-OEM 6260.6A. Portsmouth, Virginia. Available at:
  3. Department of the Army and Air Force Technical Bulletin (2003). Heat Stress Control and Heat Casualty Management. Available at:
Posted on by Brenda Jacklitsch, MS

38 comments on “Keeping Workers Hydrated and Cool Despite the Heat”

Comments listed below are posted by individuals not associated with CDC, unless otherwise stated. These comments do not represent the official views of CDC, and CDC does not guarantee that any information posted by individuals on this site is correct, and disclaims any liability for any loss or damage resulting from reliance on any such information. Read more about our comment policy ».

    The decrease in the ozone layer is causing great damage not only in skin exposed to sun and heat but also in cell receiving ultraviolet rays capable of killing bacteria.

    Any studies ever done to measure the difference in heat tolerance between workers in the north versus workers in the south? Although there are no OSHA standards for heat exposure (standards can be referenced at ), the inspectors up north seem more concerned during a heatwave than the ones down south. Aclimation, I guess.

    I am not aware of any studies that have measured the difference in heat tolerance between workers in the north compared with workers in the south. Heat tolerance or acclimatization occurs over a 7 to 10 day period and physiological adaptations occur. These adaptations can include increased sweating efficiency, stabilization of the circulation, and work can be performed with a lower core temperature and heart rate. Since some regions in the south may have higher temperatures for longer periods of time compared to northern regions, it may be that those southern workers are able to hold onto their acclimatization for longer periods of time. However, with any seasonal shift in temperature that lasts about a week, workers will lose their acclimatization. Any heat wave should be a matter of concern no matter the location, because the increase in temperature that occurs will not give workers time to acclimatize.

    Workers who are exposed to extreme cold or work in cold environments may be at risk of cold stress. For more information, visit the NIOSH cold stress topic page.

    The NIOSH health hazard evaluation program has evaluated heat stress in many occupational settings. Recent reports address heat stress in an aluminum smelter and during wildland firefighting. You can find these and other reports by entering the term “heat stress” on our search page to find reports of interest.

    Through NIOSH’s Fire Fighter program, NIOSH has also investigated the deaths of several fire fighters where heat stress may have precititated a cardiac event or caused heat stroke. Of the heat stroke deaths have all occurred during training: live-fire training or physical fitness training.

    The reports can be found at the following link scroll down to “medical” and click on heat stress.

    Workers such as landscapers, construction crews, police officers, postal employees, and others who spend most of their days in the heat often have little time for bathroom breaks or for drinking fluids, as a result these workers may not consume enough fluids during their workdays.

    Don’t forget bus drivers and restaurant workers. Due to management not allowing breaks or providing restroom facilities, bus drivers and line cooks often become dehydrated at work. This can lead to serious kidney problems or more acute sickness if the work environment gets too hot.

    I think that worker must be in the best conditions to do their work and it’s hard to work when it gets too hot.

    Interesting that this is a fact that i dont know..”Acclimatization can usually be maintained for a few days of non-heat exposure, so taking a break in the air conditioning will not reduce a worker’s level of acclimatization. And it is a very effective way for workers to cool down in a fairly short period of time. ”
    Hopefully many workers can understand about also Myth about drinking eight glasses of water a day []

    I have done a number of studies on heat illness and I thoroughly enjoyed your article. I believe that it could be a good idea to rest in air conditioning however it will not really help you acclimatize. It is EXTREMLY important to hydrate and people should know better than to go out in the heat without proper hydration.

    When I go hunting some of this happens to me and the only think is to try to prevent by wearing white clothes, having a lot of water and shade.
    Acclimatization occurs when a person is exposed to extreme environmental conditions over a 7-10 day period. However, during heat waves air temperatures rise above normal quickly, and workers will not be able to immediately acclimatize to the new, hotter temperatures. During heat waves, workers will need more breaks and rescheduling some of the harder and hotter job tasks may be warranted.

    Such an interesting fact that i really don’t know… thanks for this, by staying hydrated is the most important thing on the list..

    I notice a lot of articles related to heat illness in an outside environment, and few that relate to illness/stress/stroke caused in an indoor environment. Occupations such as Boilermakers, Industrial workers, Construction or Carpenters building Scaffold around an active Boiler, ect. are all exposed to the same affects of the heat; and at times the conditions can be much worse than working outdoors. An active boiler radiates heat in an access of 160 degrees F. I feel this issue is overlooked, yet workers are exposed to these elements daily.
    My husband is currently suspended 800 feet above ground level, building scaffold around an active boiler. The boiler radiates such strong heat, within the first hour of work he is already drenched in sweat and suffering mild heat related stress symptoms. The heat is so extreme and dry, his eyes can not and will not water and it sucks all the moisture from his body. it It is his responsibility to know his own limits and he will take breaks as needed. If a worker pushes their limits too far, being afraid of looking like a “wimp or sissy” this could mean life or death, or permanent disability. His employer pushes the worker safety off on the plant, but it is not the plant’s responsibility to ensure the safety of the workers they do not employ; that is why work is subcontracted out to other companies.
    After a day of working in these conditions, he has a difficult time driving home; as he is so exhausted from the extreme, dry heat’; often almost falling asleep from such exhaustion.

    Really it’s all about how the company you work for follows safety standards related to extreme heat exposure. I am a roofer in AZ , today it will be 115 with 30% humidity plus you must add 40-50 degrees to air temp to get your roof temp. Plus I feel companies should have a buddy system we’re each guy looks after the guy/girl working nearest to them and look for signs of heat illness.
    Having potassium and electrolytes on hand is important but it’s also important to consume these before your body starts to cramp or heat stroke.
    If you’re company is working you in the hottest point of the day then they don’t care about safety. Starting work at 2am is the key as long as you have good lighting.
    Remember it’s all about going home safely everyday.

    I agree with you. It’s unethical when employers aren’t providing an adequate amount of “PORTABLE” drinking water for their employees while working on or near boilers systems.
    I appreciate reading your input on the matter.

    Drinking 1 cup of water every 15-20 minutes is a fantastic idea, however constant trips to the water fountain or carrying water bottles can be a pain. A great solution is getting a proper hydration system. Great Article!

    Living in Las Vegas, this is a real concern on a daily basis. Great to know that some workers carry umbrellas for the job site just to keep out of the sun. Workers must keep hydrated and managers must consider heat stroke prevention. Thanks for the great article! If OSHA does release safety training guidelines, check sites like and

    Wish at least some of the advice here – wet cotton clothing, head covers, adequate drinking / cooling water – were insisted by the administrations during this summer in India. We could surely have prevented some of the 2300 plus deaths.

    This is really a good information for all people where you maintioned some problem related to the hydration and you are focousing on workers which is graet thinking to provide them a workfriendly inviroment.

    I hope NIOSH’s updating of it’s 1986 heat stress document shall be addressing the cause of the vast majority of heat stress illness: Chronic Hyponatremia. The only mention I can find of hyponatremia by NIOSH is in a 2000 report that defines it as “Water Toxicity”. A better definition for hyponatremia is where serum sodium falls below 135 mEq/liter.
    Your promotion of drinking before being thirsty and a cup every 15-20 minutes is dangerous and admonishment against salt tablets is irresponsible. I would had been hospitalized for hyponatremia if I had taken this now nearly universally given advice. The CDC’s campaign against sodium consumption fails to account for subsets of the population which are not eating enough salt.
    The appropriate advice is to drink only to thirst and eat salt to taste (ie until it tastes unpalatable). You don’t see deer lick till it’s sick on salt. Perhaps that’s the problem, deer don’t think about whether its eating too much salt.
    Dehydration is a myth in causing heat stress illness, it accounts for little if any heat stress illness. The simplest way to show the dehydration myth comes from policemen regularly killing their K-9 dogs inside hot vehicles. None of those dogs were dehydrated because dogs don’t sweat.
    13% of 2002 Boston marathon finishers tested (488) had hyponatremia. 3 were asymptomatic with severe hyponatremia. The woman from that marathon who died from Gatorade intoxication had a 125 serum sodium, higher than the 3 asymptomatic individuals.
    The American College of Sports Medicine is a quasi science corporate front whose research articles always have “drink more Gatorade” as the answer. Gatorade is a hypotonic liquid masquerading as a “sports drink”. I suggest the New England Journal of Medicine is a better reference than the one you provide. Your Navy reference concedes use of salt tablets may be needed at times. I don’t understand why you listed the army reference because you ignore page 38.
    A notable absence of medications mentioned causing heat illness are Selective Serotonin Reuptake Inhibitors. The NIOSH FACE investigation of the dead Michigan Lawn Mower operator in 2002 included unreliable drug measurements to declare the decedant overdosed on Prozac. The manner which SSRI’s account for heat stress illness comes from Syndrome of Inappropriate Antidiuretic Hormone Secretion. SIADH could easily add 10 pounds of sodium deficient fluid to an adult male causing hyponatremia. The NIOSH report fails to discuss the possibility of fluid retention. On the other hand, the investigator notes Seroquel can cause heat illness. I find nothing indicating a mechanism for Seroquel causing hyponatremia. In my opinion, Prozac was used in a therapeutic dose causing SIADH that caused fluid retained chronic hyponatremia leading to heat stroke.
    This blog is sadly representative of how the government falls short in addressing heat stress illness.

    Thank you for your comment. The newly revised Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments should be released by early 2016.

    Great post,I think that worker must be in the best conditions to do their work and it’s hard to work when it gets too hot.

    Great post! employer should make a policy on this issues. Worker’s hydration should be discussed and make it as a focus area in any organization.

    We run into these issues a lot out here in Las Vegas. Folks come in from out of town and forget to take care of their bodies and then end up paying for an expensive ambulance ride simply because they weren’t hydrating or eating right.

    I like some of the suggestions in the comments that incentivize hydration at the workplace. Perhaps another approach would be to encourage onsite medical care at work or at events, which would give folks greater access to health professionals and generate a more positive mindset about staying healthy consistently.

    We talk about some of these ideas on our website and look forward to any more ideas here!

    Someone should share these suggestions with the [name removed] who have workers sitting out in the heat everyday for hours and not allowed to leave their post to obtain additional ice during the day. This while they are waiting on donation’s. They only make 7.00 an hour so it is difficult to afford ice every day.. So when you drop offitems, drop off a couple bottles of water.

    Are there any guidelines on vessels for hydration in environments where there is hazardous dust potential. If it is severe hazard, such as asbestos or thick heavy metal dust, hydration would have to occur in a non-contaminated environment. When the hazard does not rise to that level, but workers and employers want to minimize the chance of ingestion of harmful dust from personal water bottles, are their practices or products that are recommended? I was unable to locate information on the topic.

    This was a very meaningful post, so informative and encouraging information, Thank you for this post.

    Great post! Employers should create policies addressing hydration. Ensuring workers stay hydrated should be a key focus in any organization. Discussing and implementing hydration practices can greatly improve employee health and productivity. Thanks for highlighting this important issue!

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Page last reviewed: June 8, 2018
Page last updated: June 8, 2018