1. Preventing Heat Stress in Nursery/Landscape Workers
Trent Teegerstrom
University of Arizona
In collaboration with Dr. Howard Rosenberg
University of California at Berkeley
This presentation covers information on how to prevent heat stress in workers commonly exposed to outdoor conditions. The presentation may be used for training employees and reminding them of the potential hazards heat stress can cause.

2. True or False ?
1. High temperature stresses the body because the surface blood vessels expand and the pulse rises.
2. Medical hazards are the only hazards that stem from heat stress.
3. As long as a person is sweating, the body is being cooled.
4. In hot temperatures, dizziness can result from operation of the body’s cooling system.
5. If you don’t feel thirsty, there is no need to drink water.
Take a moment to answer these questions. If you are not sure about the correct answers, try to find the answers during the following presentation.

3. Outline Basics of how heat stress affects the body
Conditions caused by heat stress
Controlling heat stress
Practical issues for nursery/landscape
How to prevent heat stress in workers
The presentation will follow this outline. Understanding how the body copes with heat stress and the conditions that result from heat stress are a first step in mitigating the problem. Tips on how to prevent heat stress, especially for workers in the nursery and landscape industry, are presented. The information is useful for all workers who work long hours outdoors while performing moderate to strenuous tasks.

4. Heat stress (total net heat load on the body)
= heat from external sources (environmental)
plus (+) internally generated heat (metabolic)
minus (-) heat lost from the body to the environment
The result of heat stress on a person is the total net heat load on the body. This is a combination of the heat in the environment a person is exposed to, plus the heat that is internally generated (by both working and cooling the body), minus the heat lost from the body to the environment through cooling.

5. Physiology of heat stress
During both rest and activity, the human body tries to maintain an internal temperature of 98.6°F.
Hot weather, heat sources, and hard work raise the body’s core temperature.
Heated blood is pumped to the skin’s surface where excess body heat is lost to the cooler outside environment.
If more heat needs to be shed, the evaporation of sweat aids in cooling.
During heavy work, a person can lose 1- 2 liters of water per hour.
After 2-3 hrs a person may loose endurance, become uncomfortable, feel hot and become thirsty.
This slide and the next describe some key points of the physiology of heat stress. It emphasizes the important role water plays in counteracting heat from the environment and heat generated from physical activity and the body’s cooling mechanism.

6. Physiology of heat stress (continued)
The longer a body sweats, the less blood there is to shed excess heat or carry oxygen and nutrients to muscles.
After 3 hours, a dehydrated worker may experience:
Headaches, muscle fatigue, loss of strength, loss of accuracy and dexterity, heat cramps, reduced alertness, nausea
Water is key to cooling the body and counteracting heat stress.
Without fluid replacement during an extended period of work, the body may be in serious danger.
Untreated heat exhaustion may lead to heat stroke.
Without rehydrating the body, other important body functions are impaired and a dehydrated person exposed to heat while performing physical tasks will eventually display minor to major symptoms of heat stress.

7. Heat stress effects if no fluid is replaced
Dehydration Cumulative Fluid % Body Wt Time to Symptoms and
Loss Reach* Effects
Minor Dehydration 1.5 lb. (.75 L) % hr Generally unperceived
Incipient Stress 3.0 lb. (1.5 L) % hr Begin thirsty, hot,
minor discomfort .
Advanced Stress 4.0 lb. (2.25 L) % hr Loss of energy, muscle endurance.
Heat Cramping 6-9 lb. (3-4 L) % hr Impaired coordination, endurance. Less energy, strength Fatigue, cramps.
Heat Exhaustion 9-12 lb. (4-5.5 L) % hr Headache, dizziness, nausea. Serious fatigue.
Heat Stroke 11+ lb. (5+ L) % hr High body temperature, confusion. Loss of consciousness.
* based on a 150 lb. male performing moderately active work in hot weather and not drinking to replace fluids
This chart summarizes how cumulative fluid loss of a 150 lb male performing moderate work in hot weather and not drinking to replace fluids affects the person’s body weight and describes the symptoms and effects of progressive dehydration.

8. Summary The physiological responses of the body to heat are:
Increase in “core” body temperature
Increase in heart rate
Increase in blood flow to the skin
Loss of water and salt (sweating)
Heat illness that impairs cooling mechanisms
This simplified summary lists the key points on how a body reacts to heat.

9. Environmental factors that affect body heat gain and loss
Air Temperature
Air Movement
Humidity
Radiant Heat
Altitude
Environmental conditions effect how the human body gains or loses heat. Higher air temperature, humidity, and radiant heat will increase a body’s heat gain. Air movement under high temperatures can bring some relief by helping increase evaporative cooling under high temperatures, while stagnant air counteracts evaporative cooling. At higher altitude (lower oxygen levels) heat is more difficult to dissipate because the body is already deprived of oxygen compared to a person at low elevation (higher oxygen levels).

10. NWS Heat Index
This heat index chart from the National Weather Service illustrates the fact that above 86°F the apparent temperature becomes dependent on the relative humidity. Higher humidity at the same temperatures will feel warmer to a person and will make it more difficult for the body to dissipate heat. The different colors in the chart indicate when exposure to the combination of temperature and humidity conditions can become a health risk. For workers performing physical tasks outdoors or in poorly ventilated structures, this chart can become a guide to issue heat-alerts.

11. Average high temperatures in AZ + CA (Average annual high temperatures for each 40% humidity)
May Jun Jul Aug Sep Oct
Phoenix
Tucson
Flagstaff
Yuma
Prescott
Bakersfield
El Centro
This table shows the average monthly high temperatures for different cities in Arizona and California. Orange and red numbers indicate danger and extreme danger, respectively, based on the previous heat index chart. While these historic values can be valuable to know when to expect potential problems with heat stress, actual environmental conditions need to be monitored and assessed to prevent heat stress.

12. Personal factors affecting tolerance
Activity level (metabolic heat)
Fluid intake and electrolyte replenishment
Alcohol and drug use
````````````````````````````````
Acclimatization
Age
Physical fitness
Body fat
Diet
Each person’s tolerance to heat stress varies and depends on a number of individual factors that are listed above.

13. Issues exacerbating heat stress in the nursery and landscape industries
Unconditioned environment
High temperatures and humidity
Physically demanding work
Misread as or combined with pesticide exposure
“Costs” of access to water
The majority of work in the nursery and landscape industry occurs outdoors. Workers are exposed continuously and often perform physically demanding work. Most nurseries routinely use pesticides and symptoms of heat stress can easily by misread as symptoms of pesticide exposure. Accessing drinking water can be a burden for workers who don’t carry their own water and who have to walk a distance to reach a water source.

14. Causes of Serious Injury in AZ Nursery and Agriculture Industries 2001-02
Caught or struck by equipment (32%)
Machinery and vehicles operation (26%)
Overexertion (21%) (including heat stress)
Falls (11%)
Other (25%)
electrical, chemical, livestock
Reported serious injuries in the Arizona nursery and agriculture industries are led by accidents involving equipment or machinery. Overexertion including heat stress accounted for about one fifth of the injuries.

15. Other Hazards of Heat Stress
Besides the medical hazards of illness or injury caused by heat stress, there is also a higher frequency of accidents in hot environments.
Direct causes of accidents:
Sweat in the eyes
Slippery hands
Fogged glasses
Dizziness or fainting
Indirect causes of accidents:
Physical discomfort
Slower mental and physical job reactions
Diverting attention from the job
Lapse in judgment
Irritability and anger
Heat stress of workers may have contributed to some of the accidents because a person had sweat in the eyes, slippery hands or felt dizzy from the heat and was unable to operate a vehicle or machinery safely. This list of direct and indirect causes of accidents can be linked to heat stress. While an accident is not necessarily caused by heat stress itself, impaired conditions of workers exposed to heat stress are more likely to result in accidents than in a more comfortable working environment.

16. Heat and Pesticide Exposure
Symptoms of organophosphate and carbamate pesticide exposure are similar to those of heat stress
How much misdiagnosis ?
Since symptoms of organophosphate and carbamate pesticide exposure are often similar to heat stress, some heat stress symptoms may be misdiagnosed as pesticide exposure symptoms. The following slides lists a comparison of both symptoms. It may be helpful if workers are familiar with those symptoms and can respond rapidly to mitigate detrimental effects.

17. Symptom Comparison Heat Stress Pesticide Exposure Sweating Headache
Fatigue
Dry membranes
Faster pulse
Nausea
Dilated pupils
CNS effects
Coordination loss
Confusion
Fainting
Pesticide Exposure
Sweating
Headache
Fatigue
Most membranes ok
Slower pulse
Nausea and diarrhea
Small or normal pupils
CNS effects
Coordination loss
Confusion
Coma
This list shows the similarity between heat stress and pesticide exposure symptoms. Since many symptoms are non-specific, other causes cannot be ruled out and medical attention should be sought to diagnose and treat the actual problem. Note: central nervous system (CNS).

18. Coping with the Hazards
Planning, training, and supervision are key to preventing heat disorders
Understand the effects of heat stress
Know the symptoms and treatments
Take personal precautions
This last segment of the presentation deals with how to prevent heat stress in workers. Factors to consider are planning, training and supervising workers to ensure that potential problems can be prevented as much as possible.

19. Preventive Measures to Consider
Consider current and predicted weather conditions, issue heat-alert if necessary
Evaluate and modify work assignments
Adjust rest period frequency and length
Schedule heavier jobs for cooler hours
Provide shade for stationary work
Help workers become acclimatized
Medical exam to identify need for accommodation
Train / educate -- recognition, treatment, physiology
Use cooling garments
Find lighter weight protective gear
Provide cool places for breaks
Improve fluid replenishment
This list of preventive measures to consider is by no means complete, but it may help to keep important issues in mind: considering environmental conditions, the type of work that needs to be done and the level of exposure and exertion associated with it, physical condition of workers, opportunities to protect workers from heat and opportunities to help hydration of workers.

20. Providing shade for stationary tasks such as filling pots with media can help
mitigate exposure to heat.

21. Fluid Replacement Guidelines
U.S. Military & NIOSH Research:
25 oz./hr. during moderate work at 82-90°F
33 oz./hr. during heavy work at >90°F
Drink small amounts frequently (drip, not flood)
Don’t wait for thirst
Rest every hour: “Rest means minimal physical activity such as sitting or standing. The following examples will vary depending on individual and circumstances)
Moderate work in moderate heat (85-89°F) work/rest 40/20 min
Moderate work in High heat (>90°F) work/rest 20/40 min
Hard work in moderate heat (85-89°F) work/rest 30/30 min
Hard work in high heat (>90°F) work/rest 10/50 min
Fluid replacement and rest guidelines by the U.S. military and NIOSH research may not fit every work place. However, the advice to drink small amounts of water frequently and to drink before becoming thirsty are important measures to prevent heat stress. Workers should learn that following these guidelines increases their performance and can prevent problems in the long run.

22. Do current means of providing water effectively address risk of heat stress?
Typical ways to provide water to workers in the nursery or a landscape include an igloo mounted on a truck or placed in a field, personal water bottles, or backpack or hip mounted personal hydration devices.

23. Drip vs. Flood Irrigation in Sport
Personal hydration systems enable cyclists to hydrate on the move.
Cyclists can keep going, save time, and maintain high speed.
Exercise research shows increases in fluid consumption and performance using a hydration system vs. traditional container.
Personal hydration systems compared to traditional containers helped cyclists save time while maintaining high speed while maintaining better performance and hydration. Smaller amounts of water consumed more frequently were better than larger amounts consumed less frequently.

24. Employer testimonies:
O’Reilly Auto Parts Warehouse piece rate work environment. Field test initiated by the Risk Manager . . .
“The use of a CamelBak hydration system has increased our productivity by 20%.”
Berry producer in Oxnard Agricultural workers in the field. Field test initiated by the Safety manager.
“Every single person that used a CamelBak hydration system in our study % of them -- had an increase in productivity.
These testimonies from companies using one type of personal hydration system demonstrate the benefits of regular hydration in productivity.

25. Casual Observations: Water Availability versus Intake
Igloo is state of the art for many field operations.
Workers walk to reach water, distance varies.
Costs to access water are not only physical.
Infrequent visits to igloo are thirst-driven.
Large quantities are then drunk at each visit.
Less access taken while on piece-rate basis.
Faster pace of work in the morning.
Workers have little understanding of how heat affects the human body.
Are workers chronically underhydrated and show subacute symptoms of heat stress?
The reason why workers may not drink enough and why they do not drink often enough can be due to a number of issues. Including but not limited to the distance to an igloo/water, the type of pay system being used (piece-rate), peer pressure etc. However, research has shown that frequent hydration with small amounts of water is more effective than large amounts of water consumed less frequently. Since workers may not understand how the human body deals with heat, they may not be aware of the additional strain on a body that is becoming dehydrated in a hot environment. It is also likely that many workers arrive at work in the morning already under-hydrated and that they may suffer chronically from subacute symptoms of heat stress.

26. OSHA General Duty
“...every employer covered under the Act furnish to his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to employees.”
OSHA regulations stipulate that workers are provided with a place of employment free from recognized hazards that are causing or are likely to cause death or serious physical harm to employees. Heat stress can cause serious physical harm if not recognized and treated. Planning, training and supervising with the goal of preventing heat stress can mitigate potential problems in the workplace.

27. “Ideal Heat Stress Standard”
Simple
Inexpensive to implement
No interference with production
Easy to enforce
Each company should decide on what practices work best in order to prevent the incidence of heat stress. These measures should be simple and inexpensive to implement, not interfere with production, and should be easy to enforce. For example, providing equipment operators who spend long hours under hot conditions with a personal hydration system could prevent dehydration and may keep them more alert. Or when the heat index approaches hazardous conditions, outdoor work will only be scheduled until noon, and workers will be assigned to other duties in less hazardous conditions during the hottest part of the day.

28. Recommended Training Objectives: Enable Workers to . . . .
understand how a body responds to heat, function of the body’s cooling system, factors that affect body heat gain or loss, and effects of heat stress.
know and effectively use prevention measures.
describe causes and symptoms, and be able to give initial aid to others with minor heat stress disorders.
describe the causes and symptoms, and be able to give or obtain first aid for others with major heat stress disorders.
Training workers and supervisors will be a key component to prevent heat stress and recommended training objectives are listed in this slide. Parts of this and other presentations on this website can be used and tailored to fit a particular training session or sessions. When asked why workers often don’t drink enough, they don’t perceive that they become dehydrated, they often overemphasize the ‘cost’ of getting water, and they don’t understand how the body functions in a hot environment. Learning about those facts will hopefully help workers to change their habits and adopt routines that will help them to avoid the detrimental effects of heat stress.

29. Additional Resources Heat Stress in Agriculture, U.S. EPA
Cal/OSHA Advisory Committee
Additional resources on heat stress and it effects can be found on the websites listed above.