MRO Magazine

It’s time to be concerned about heat and hydration in the workplace

Hamilton, ON -- It's humid and the temperatures are soaring; you've been working hard for hours. You feel dizzy, have a pounding headache, and your intense thirst suddenly reminds you that it's been hours since you've paused to drink something....

Hamilton, ON — It’s humid and the temperatures are soaring; you’ve been working hard for hours. You feel dizzy, have a pounding headache, and your intense thirst suddenly reminds you that it’s been hours since you’ve paused to drink something. You may be dehydrated, and that can cause severe health problems if left unchecked, according to an article in the Health and Safety Report, published by the Canadian Centre for Occupational Health and Safety (CCOHS), based in Hamilton, ON (

About 60% of your body is made up of water. Water is essential to human life; you need it to keep your body functioning properly and to regulate your body temperature. It flushes out wastes and toxins, helps digestion, lubricates the joints and eyes, and keeps skin healthy. You can’t live without it.

When you don’t drink enough fluids to replace the water that you lose through sweating and everyday activity, you can become dehydrated. When the normal water content of your body is reduced, it upsets your body’s balance of minerals (salts and sugar), which affects the way that it functions. Just a small drop in body fluids will cause a loss of energy in the average person; a 15% drop in body fluids can cause death.

How you can become dehydrated


There are several factors that can contribute to dehydration: environment, amount of physical activity, illnesses or health conditions, and diet.

Working outside in sun, heat, and humidity can cause you to sweat and lose fluids rapidly. Heated indoor air also can also cause loss of fluids. Being in high altitudes, greater than 2,500 meters (8,200 feet), may increase the amount you urinate and quicken your breathing, in turn, using up more of your body fluids.

If you do strenuous work or intense exercise that causes you to sweat, you are at increased risk for dehydration. You can also become dehydrated as a result of an illness or a health condition. Fever, vomiting or diarrhoea cause your body to lose additional fluids, as would a condition such as diabetes that causes frequent urination.

Drinking too much alcohol can dehydrate you. As well, drinking sugary soda and coffee to hydrate yourself can actually dehydrate you even more. These drinks usually have caffeine in them which can cause you to urinate more. Also, drinking anything loaded with sugar makes the body work hard to process it, causing further dehydration.

Signs of dehydration

Dehydration can be described as mild, moderate or severe. Watch for the following signs.


excessive thirst

dizziness or light-headedness


fatigue or drowsiness

dry mouth, lips and eyes

dark yellow urine

urinating only small amounts, infrequently (less than three or four times a day)

Moderate dehydration causes you to lose strength and stamina, and is the main cause of heat exhaustion. You should be able to reverse this level of dehydration yourself by drinking more fluids.

If dehydration is ongoing, it can affect your kidney function and cause kidney stones, liver, joint and muscle damage, cholesterol problems, and constipation.


Untreated mild or moderate dehydration can lead to severe dehydration, which is a medical emergency that requires immediate medical attention. Watch for the following symptoms:

dry, wrinkled skin that falls slowly into position when pinched up

unable to urinate or not urinating for eight hours

feeling drowsy, disorientated, and irritated

sunken eyes

weak pulse

rapid heartbeat

cool hands and feet


blood in your feces or vomit

Mental performance and concentration begin to decrease as you become increasingly dehydrated, affecting the safety of yourself and those around you.

What employers can do to help prevent dehydration

Employers have a duty to provide and maintain a safe working environment.

Educate employees on the causes and to recognize the symptoms of dehydration, and instruct them on how to protect themselves.

Continuously reinforce the messages with ongoing training and visual reminders (posters, for example) to encourage employees to hydrate themselves, and watch for signs of dehydration.

Ensure there is a buddy system in place so workers can monitor one another for signs of dehydration.

Make drinking water readily accessible and encourage your employees to drink often.

Where possible, plan the work so that more strenuous work is done during cooler periods.

Provide shade or shelters as relief from heat and rest areas for outdoor workers.

Have an emergency plan in place that includes procedures for providing affected workers with first aid and medical care. This plan is a necessity especially in extreme environments.

What employees can do to prevent dehydration

The recommended daily intake of fluids can vary depending on the individual and on factors such as age, climate, and physical activity.

Drink plenty of fluids to replace the fluids you are losing, at least a cup every 15 or 20 minutes. The fluid could be water, semi-skimmed milk or fruit juice. Sports drinks designed to replace body fluids and electrolytes may be taken in moderation.

Fluid intake should equal fluid loss. On average, about one litre of water each hour may be required to replace the fluid loss.

Avoid caffeine and sugary drinks, and NEVER consume alcohol (e.g. beer) to hydrate.

Monitor your urine color; it should be clear to light yellow. If it is darker or concentrated, you may be dehydrated, and you must drink more fluids.

If you or a co-worker begin to show signs or symptoms of dehydration, call for medical help immediately. While you are waiting for help, move to a cool place to rest. If not treated immediately, severe dehydration can lead to complications and even death.

Additional resources are available at: This article first appeared in the CCOHS Health and Safety Report and can be found at