Working outdoors in hot weather can put yourself and employees at risk for heat exhaustion or heat stoke. Heat exhaustion is a serious health problem, and heat stroke can kill.
More information is available at http://deohs.washington.edu/pnash/heat_illness
By Helen Murphy,
Pacific Northwest Agricultural Safety & Health Center
Two Washington State agricultural workers have died of heat stress in the past decade.
In one case, it was mid-May and about 78°F in Yakima. A 35-year-old worker started his job at 9 a.m. By early afternoon, he complained of feeling tired. As he went to lie down, he suddenly collapsed, became delirious, and had a seizure. His recorded temperature in the emergency room was 111°F. The cause of death was heat stroke.
Chances of survival are pretty good if the body temperature is lowered to at least 102°F within 30 to 60 minutes. The worker described above probably died because of the intensity of his temperature.
Many cases of heat illness are misdiagnosed. By the time workers reach an emergency room, their temperature may have fallen enough that heat illnesses aren't suspected. Symptoms may be misclassified as those of a heart attack. Less severe cases may never get reported because workers don't recognize heat-related illnesses or don't want to let their teammates or employer down.
Heat stress is a build-up of heat from the body's own work plus external (environmental) sources. If more heat is generated than can be released, you become heat stressed. A heat-related illness results when the body can no longer cope. The body's physical and mental functions break down. The heart responds to a rise in body temperature by pumping more blood to peripheral vessels, which enlarge or dilate to release heat. If that isn't enough, you will start sweating to cool down by evaporation.
Classically, exhaustion causes profuse sweat and cool, clammy skin. Move such a person out of the heat, provide fluids as tolerated (sips of a sports drink if available), strip off any extra clothing, and cool the person by wetting clothing and fanning him or her. Medically evaluate the victim.
There are three ingredients: temperature, high humidity, and the absence of air movement. Humidity was a factor in the case above, because the worker was in an irrigated area. High humidity reduces the body's ability to get rid of excess heat by sweating and so increases the apparent temperature (see figure "Heat Index" on facing page).
Machinery can add to the sun's heat.
For more information and illustrations, including a chart explaining the signs and dangers of heat illness, which can be printed out as an educational tool, go to the Good Fruit Grower Web site at http://www.goodfruit.com/
What are the Dangers of Heat Stress?
| Heat Cramps | Heat Syncope (Fainting) | Heat Exhaustion | Heat Stroke | |
|---|---|---|---|---|
| Description | A temporary fluid and electrolyte imbalance- salt depletion in conditions of heavy physical exertion | Pooling of the blood in the lower extremities in unacclimatized workers who are required to stand in the heat for long periods of time. | A reduction of body water content or blood volume. It occurs when the amount of water lost (as sweat) exceeds the volume of water taken in during the heat exposure. | Body fails to regulate core temperature. Sweating slows or stops completely preventing the body from releasing the excess heat. |
| Symptoms | Painful muscle spasms in the arms, legs, and abdomen | A brief loss of consciousness. In a worker who is performing any substantial labor, consider it HEAT STROKE, call 911, and cool down immediately by any method. | Profuse excessive sweating, cool clammy pale skin, weakness and fatigue, dizziness, nausea and vomiting, weak rapid pulse and early neurological symptoms (e.g. headache, anxiety, or impaired judgment) | Same as heat exhaustion + core body temperature >104º, altered mental status (irrational behavior, psychosis, aggressive behavior, incoherent speech), the skin can be hot, flushed, pulse may be bounding and rapid. |
| Consequences if Untreated | May be accompanied by heavy sweating and thirst, heralding impending heat exhaustion. | Loss of consciousness regained once the person falls to the ground. Watch for injuries secondary to falling. | If left untreated may rapidly progress to HEAT STROKE and subsequent death. | Loss of consciousness, coma, organ failure and death. |
| Treatment | Rest in a cool environment. Give fluids and salty foods or an electrolyte solution such as sports drinks. Salt tablets are not recommended due to the risks of overdosing. | Keep the individual lying down with feet raised, cool with wet cloths and ventilation, provide fluids and then move to a cooler location. Do not return to work and refer for medical evaluation. | Transfer to a cool shaded place. Cool body with wet clothes and ventilation. Replace water and salts; a good source for both are sports drinks. Transfer to a medical facility for evaluation. | Call 911! Cool down the body immediately with every available means- most effective is a ice water bath or wet down entire body with copious amounts of water and vigorously fan. |
Adequate hydration is the most important step to combating heat stress. When the heat index is high, workers should drink copious amounts (1 quart every hour) frequently throughout the work shift: they should consume at least one cup every 15 minutes or a pint every half hour - in order to stay properly hydrated. Workers should be trained not to wait until they feel thirsty to drink; if they are thirsty they may already have lost 2% of their body’s water. The onset of heat exhaustion can begin after losing 3% of the body’s water and heat stroke occurs once 8% is lost. The bottom line is, if a worker is not regularly urinating or has dark urine, they are dehydrated and at risk for heat illnesses!
Assess the relative danger of the worksite. Be aware that high heat, high humidity, low air circulation all create a more dangerous working environment. Any time more than one of these variables is present, the danger is compounded. Wearing occlusive non-breathable clothing in combination with heavy exertion compounds these worksite risks and can alone lead to heat illness.
If an employee is new to a job or is returning after time away: ease them back into full-time work over the course of 5 days. Starting at half time (50% effort) and increasing to full time (increase by 10% each day) can greatly reduce the employee’s susceptibility to heat stress.
July 1st, 2007
Vol. 58 No. 12
PACIFIC NORTHWEST AGRICLUTURAL SAFETY AND HEALTH CENTER
(800) 330-0827, http://depts.washington.edu/pnash/
Rev. 2/07
Disclaimer and Reproduction Information: Information in NASD does not represent NIOSH policy. Information included in NASD appears by permission of the author and/or copyright holder. More
