IS1539 Worker Protection Standard: Heat Illness

Worker Protection Standard

Heat Illness

Heat illness is the result of overheating the body. Mild cases of heat stress can cause the victim to feel ill, tired, and weak. More serious heat illness can exhibit itself as headache, nausea, dizziness, severe thirst, and fainting. Severe heat illness (heat stroke) causes death in more than 10 percent of victims, including healthy adults.

Prevention

There are things you can do to help prevent heat illness. When possible, work in shaded areas or in a building with adequate ventilation. Spend as little time as possible in direct sunlight. Take notice of high temperatures, high humidities, and air movement before starting a job. When using a chemical for which personal protective equipment (PPE) is required, use the minimum equipment necessary. Extra equipment will cause unnecessary stress from the excess heat. Use equipment that will keep you as cool as possible. Woven coveralls, if allowed by the pesticide label, will keep a worker cooler than will coveralls treated with a protective chemical seal. If a respirator is required, a battery-powered respirator that forces filtered air through a helmet can help keep the user cool.

Allow yourself time to adjust to working in the heat. Begin by working in the heat about 2 hours per day for several days in a row. Then increase the workload gradually over the next several days, until you have adapted to the heat.

If possible, schedule the heaviest outside work during the cooler times of the day. During the hottest times of the day, schedule frequent water breaks. Under extremely hot conditions, it is wise to wait for cooler temperatures before continuing outside work.

Drink plenty of water before, during, and after working in heat. Sweating cools the body, and failure to replace the water being lost by sweating increases the body's temperature. A dangerous amount of water can be lost before the victim feels thirsty, and thirst may stop before enough water has been taken in to replace the sweat. Drink water whether or not you think you need it.

First Aid

Learn to recognize the symptoms of heat illness. If someone is affected by the heat, take immediate actions to cool the victim. Get the victim to a cool area. Cool the victim by splashing cool water on the skin, especially the hands, forearms, face, and neck. Remove the personal protective equipment and clothing that may be keeping the victim hot. Give the victim plenty of cool water to drink. Never attempt to give water to an unconscious victim. Get medical attention.

Relative humidity can add an extra element of danger to working in the heat. Humidity combines with the air temperature to produce an apparent temperature, which is the temperature your body feels.

Table 1 shows the average high temperatures for the hottest 5 months of the year. These are air temperatures measured in the central portion of Mississippi.

Table 2 shows the average relative humidities at noon for the same 5 months in the same location in central Mississippi.

Table 3 shows the apparent temperature your body would feel if the temperature and humidity in Tables 1 and 2, respectively, occurred at the same time. Remember, these temperatures and humidities are averaged over the entire month. During the height of summer, days with high temperatures of 95 and 100 degrees Fahrenheit are not uncommon, and Mississippi's high humidity makes outside work dangerous.

Table 4 shows the danger associated with exposure to various apparent temperatures. Apparent temperature ranges are classified by danger categories, and the effects the heat might have on a person are listed in Table 4.

Table 1. Average high air temperatures

Month	Degrees Fahrenheit
May	84.1
June	90.5
July	92.5
August	92.1
September	87.6

Table 2. Average relative humidities, at noon

Month	% Relative Humidity
May	56
June	56
July	59
August	58
September	58

Table 3. Apparent temperatures

Month	Degrees Fahrenheit
May	87.8
June	100
July	105
August	102.5
September	94

Table 4. General heat stress index

Danger Category	Apparent Temperature	Heat Syndrome Degree Fahrenheit
IV. Extreme Danger	Greater than 130	Heatstroke or sunstroke imminent.
III. Danger	105 to 130	Sunstroke, heat cramps, or heat exhaustion likely. Heat stroke possible with prolonged exposure and physical activity.
II. Extreme Caution	90 to 105	Sunstroke, heat cramps, and heat exhaustion possible with prolonged exposure and physical activity.
I. Caution	80 to 90	Fatigue possible with prolonged exposure and physical activity.

Note: Degree of heat stress can vary with age, health, and body characteristics.

This information was provided by the Southern Regional Climate Center.
Reference: A Guide to Heat Stress in Agriculture. Environmental Protection Agency. March 1994.

By Trent Spencer, former Extension Program Assistant, Agricultural Engineering, in cooperation with Herb Willcutt, Extension Agricultural Engineer, and Dr. Jim Hamer, Leader, Environmental and Agricultural Chemical Education (EACE), Mississippi State University. Funded by the Bureau of Plant Industry, Mississippi Department of Agriculture and Commerce. Distributed by EACE.

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.

Information Sheet 1539
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

Copyright by Mississippi State University. All rights reserved.

This document may be copied and distributed for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.

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