THE DANGERS OF HEAT STRESS

The Occupational Safety and Health Administration (OSHA) considers heat stress to be a major concern in the workplace. As such, OSHA has increasingly cited employers who fail to provide adequate controls to reduce heat stress and who fail to have an adequate heat stress management program in place.

Working in hot environments can create heat stress, which is a dangerous condition that can cause slowed reaction times, reduced energy, and difficulties with attention. This results in reduced safety, decreased efficiency, and an overall loss of productivity.

The body functions most effectively within a limited temperature range. If the temperature rises too high, the body's metabolic rate increases and its efficiency decreases. The body loses fluid through perspiration and the blood vessels dilate in an attempt to cool the body. Eventually, the body suffers from heat exhaustion or heat stroke.

Heat Exhaustion

Heat exhaustion is caused by dehydration. The symptoms include chills, light-headedness, dizziness, headache, and nausea. The body temperature is usually between 100 - 102 degrees and profuse sweating is evident.

Treatment should be to get the individual to a cool shaded area and administer fluids. If the individual is unconscious seek medical attention.

Signs of Heat Exhaustion

profuse sweating

pale or flushed complexion

moist, clammy skin

weakness and fatigue

headache, nausea, and vomiting

slightly elevated body temperature

disorientation

Treatment for Heat Exhaustion - If you suspect someone is suffering from heat exhaustion,

Remove the victim from the heat.

Apply cool, wet cloths. Fan the victim, but stop if goose bumps or shivers develop.

Give fluids if the victim is conscious. If possible, have the victim drink a mixture of one-pint water with one-teaspoon salt every 30 minutes until recovered.

Seek medical attention if there's no improvement.

DON'T:

Give any stimulant, including alcohol or cigarettes.

Apply ice directly to the skin.

Allow the victim to become so cold that he or she shivers.

Leave the victim alone.

Heat Stroke

DANGER! Heat stroke may be fatal

Heat stroke is caused by a sudden failure of the body's heat regulatory system. Heat stroke may be fatal. It initially appears similar to heat exhaustion, but can rapidly progress to manifest more serious neurological symptoms such as, disorientation, loss of consciousness and seizures. The body temperature may be higher than 104 degrees Fahrenheit. Sweating is often absent, but the skin may be quite moist from earlier perspiration. The body core temperature must be brought down immediately. The blood pressure may be low. Kidney damage occurs in about 35 per cent of cases. Muscle breakdown occurs and the excretion of muscle breakdown products contributes to kidney injury.

Signs of Heat Stroke

lack of sweating

hot, dry skin

red or spotted skin

extremely high body temperature

mental confusion

convulsions

loss of consciousness

Treatment for Heat Stroke - If you suspect someone is suffering from heat stroke,

Remove the victim from the heat.

Seek medical attention immediately.

While waiting for medical help, cool the victim by soaking the clothing with cool water or by applying cool compresses to the body.

Give water, if the person is conscious

DON'T:

Give aspirin or any other medication to lower the fever.

Give any stimulant, including alcohol or cigarettes.

Apply ice directly to the skin.

Allow the victim to become so cold that he or she shivers.

Leave the victim alone.

HOW THE BODY COOLS

About 90 percent of the body's heat is produced in the torso area by the major organs and muscle groups. The amount of heat generated is increased as the body works harder. In order to maintain a constant core temperature, the body must either give up or retain this heat as necessary. How this is accomplished depends greatly on the ambient temperature and humidity around you.

Convective Body Cooling

Under normal conditions (60º to 80º F ambient temperature), the circulatory system carries core heat toward the skin's surface. Since heat always travels from hot to cold, rather than from cold to hot, the body heat is carried away as the cooler outside air passes over the skin. This process is known as convective cooling, since the movement of air removes the heat.

Convective body cooling occurs by movement of air.

Evaporative Body Cooling

As the temperature outside begins to rise, the difference between normal skin temperature (90º F) and the ambient temperature narrows. As the ambient temperature rises above 80º F the difference between the normal skin temperature and the ambient temperature is not great enough to allow the body's internal heat to flow away from the body by convection. Instead, the body reacts by cooling itself through a process known as evaporative cooling.

When water is exposed to warm, dry air, it will evaporate into water vapor. This change of state is called a phase change and it produces a tremendous cooling effect. The body creates this phase change by secreting perspiration from our sweat glands to the surface of the skin. When the air surrounding the skin is warm and dry, this is an extremely efficient process. But as the humidity rises, perspiration can no longer evaporate to water vapor because the air is already saturated. This is a dangerous condition, since the body has no other natural mechanism to give up heat.

Evaporative body cooling occurs by evaporation of perspiration from the surface of the skin.

Vasoconstriction and the brain

When the outside temperature drops below 60º F, the body needs to reverse the process and retain its internally generated heat. This is accomplished by a process called vasoconstriction. Vasoconstriction is the restriction of blood flow to the skin surface by contraction of blood vessels. Since the body's organs must always have a flow of blood, vasoconstriction is applied only to those vessels carrying heat to the skin's surface. When the brain is fooled into thinking the temperature is cool; for example when ice is applied to the body, vasoconstriction occurs in an effort to prevent loss of heat, even though the core temperature is actually rising. This can lead to dizziness and fainting. More dangerous is the fact that the cool skin temperature physiologically feels comfortable, so you may actually work harder, creating an even faster rise in core body temperature and the risk of cardiac arrest.

Vasoconstriction retains heat in the body by restriction of blood vessels.

HOW HOT DOES IT FEEL ?

The Heat Index

Relative Environmental temperature (F)

Humidity(%) 70 75 80 85 90 95 100 105 110 115 120

0% 64 69 73 78 83 87 91 95 99 103 107

10% 65 70 75 80 85 90 95 100 105 111 116

20% 66 72 77 82 87 93 99 105 112 120 130

30% 67 73 78 84 90 96 104 113 123 135 148

40% 68 74 79 86 93 101 110 123 137 151

50% 69 75 81 88 96 107 120 135 150

60% 70 76 82 90 100 114 132 149

70% 70 77 85 93 106 124 144

80% 71 78 86 97 113 136

90% 71 79 88 102 122

100% 72 80 91 108

NOTE: A temperature of 90º F combined with a humidity reading of 90 percent can yield a heat index reading of 122º F. That's a dangerous heat index. If full sun exposure is added to the temperature/humidity mix, the heat index can rise even higher.

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Keep in mind the following cautionary guidelines for heat indexes:

90-104 F Heat cramps or heat exhaustion possible

105-130 F Heat cramps or heat exhaustion likely, heatstroke possible

130-more F Heatstroke highly likely

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AVOIDING HEAT STRESS INJURY

Hydration: Drink fluid 30 - 45 minutes before beginning work or exercise and then 1/2 to 1 cupful every 20 minutes while working or exercising. You may not feel thirsty, but your body can still be losing as much as three (3) gallons of water a day in hot weather. After working or exercising, drink more fluid than you think you need. Our body's thirst mechanism does not appear to be as effective a gauge of our fluid needs as we age.

Acclimatization: Gradually build up your tolerance to warmer weather and hot environments. It takes 4 - 7 days to get used to unusual heat.

Stay fit and don't overestimate your level of fitness: Individuals with a higher level of fitness are more tolerant of heat than those with a lower level of fitness. If you are overweight, physically unfit, suffer from heart conditions, drink too much alcohol or are not used to hot weather, you may be at greater risk of heat stress and should seek and follow medical advice. Work and exercise at a reasonable pace. Perform the most strenuous activities while temperatures are the coolest. Take frequent breaks in a cool place.

Watch your health: Make sure you are aware of both medical conditions that you have and medications that can affect your tolerance of exercise in the heat. Medical conditions affecting your heat tolerance include diabetes, high blood pressure, obesity and fever.

Dress cool: Wear lightweight, loose fitting cotton fiber clothing rather than synthetic fiber to permit evaporation of perspiration.

Avoid the sun: Stay out of the summer sun as much as possible; especially between 10:00 AM and 4:00 PM. Wear a hat and sunglasses.

RECIPE FOR YOUR OWN SPORTS DRINK

No matter how fancy the bottle, most sports drinks are surprisingly simple in composition. You can mix your own thirst quencher at home for half the price.

• 8 ounces of water - (avoid sparkling water. The gas makes it more difficult to drink)

• 1 teaspoon of lemon juice (use other flavors lime, orange, etc. as desired)

• 1/4 teaspoon of salt

• 4 teaspoons of sugar

• Mix well, chill and drink to help prevent heat stress.

CAUTION: Check with your physician if you have a physical condition that restricts or prohibits using the ingredients in this drink or if you are taking medications that may be incompatible with the ingredients.