During most harvest seasons on any Christmas tree farm, some workers will experience strained muscles and possibly a minor scrape, cut, or bruise. Occasionally, however, serious injuries can occur during harvest activities. Injuries can result in higher workmen’s compensation insurance and lost productivity during a very hectic time of year. Nationwide, such work-related injuries account for 34 percent of all sick leave. These injuries cost $15 to $20 billion in workers' compensation each year. With a few precautions and minor adjustments to harvesting practices, many of the typical injuries can be avoided.
Christmas tree harvesting activities involve a wide range of ergonomic and safety concerns associated with the high level of manual activity. Ergonomics is the science of adjusting job tasks to the worker. It is concerned with the motion and activity of people, their use of tools and machinery, and the design and arrangement of work for greatest safety and efficiency. When there is a mismatch between the physical demand of the job and the physical capacity of the worker, acute and chronic injuries can result. Employers and employees alike need to be aware of hazards related to equipment use and the way workers physically move through tasks. Greater work safety can be achieved by first identifying the high-risk activities and then altering the work conditions that contribute to possible injuries.
The factors that contribute to ergonomic stress include force, repetition, posture, and duration:
Force. High muscular force is a common ergonomic risk factor found in manual jobs. Active work such as carrying, pushing, lifting, or handling a heavy load may often require excessive force that leads to an increased risk of injury. When employees must work certain muscles too hard, blood flow is restricted leading to rapid muscle fatigue and potential injury. In a similar way, when workers hold a static position or carry a load for more than a short time, blood flow to the muscles involved is also diminished with resulting fatigue and risk of injury. Force-related injuries during harvest result from straining to lift trees or equipment, straining to hold a grasp on those loads, and from the impact of sharp or hard objects against hands, limbs, and body.
While Christmas tree harvest will always be physically demanding work, the need for excessive individual effort can be minimized. By following proper lifting techniques, working in teams, and reducing the distance that loads must be carried, workers can avoid hurting themselves. By having the right equipment for the task, such as a large baler cone to bale large trees or a longer elevator to load tractor trailers, the need for workers to strain their muscles can be greatly lessened. Try to mechanize the harvesting operation where possible to reduce the need to manually carry, lift, or catch trees and to reduce the duration and effort of such activities.
Repetition. High frequency repetition is another common ergonomic risk factor and generally increases the risk of developing a chronic injury such as carpal tunnel syndrome. Carpal tunnel syndrome occurs when tendons inside the wrist become inflamed from repetitive motion. High repetition is considered to occur when the same motion or pattern of motions are repeated several times a minute. Such repetitive tasks are most commonly seen in manual assembly jobs which involve recurring hand/wrist motion. Making wreaths, tying baling twine, or even gripping trees to drag them to a baler constitute repetitive activity. Injury could be avoided by separating repetitive tasks into jobs for different people, redesigning the work area such as adjusting the height of a wreath machine, or by implementing frequent short breaks for workers to shift positions or stretch aching muscles. Localized vibration from equipment such as chain saws can also produce a type of repetitive injury called Hand-Arm Vibration Syndrome. Providing workers with anti-vibration gloves and chain saws that have vibration-dampening components can reduce the risk of this injury. Where workers function as a team, members can switch off tasks to rest from repetitive motion or fatiguing equipment operation.
Posture. Ergonomic studies have identified the importance of correct posture in minimizing work injury. Incorrect posture becomes an ergonomic stressor when it occurs over a long period of time or accompanies excessive force. An awkward posture occurs when a joint is bent more than a quarter of its natural range of motion away from its resting position. Bending the wrists, bending the neck, raising arms above the head and shoulders, kneeling or squatting, and bending at the waist all have been identified in workplace studies as postures that contribute to the development of muscular and/or skeletal injuries. In some cases, seemingly unrelated joint postures can be important. For example, because the nerves of the hand/wrist originate from the spine in the neck region, pain in the hand/wrist can sometimes be caused by an excessively bent neck such as when carrying a baled Christmas tree on a shoulder. Bending from the waist to lift trees or equipment and lifting trees or other loads above the chest are particularly risky postures used during harvest (Figure 1).
To reduce posture-related problems during harvest, train workers to lift with their legs instead of their backs and to keep their backs as straight as possible when lifting (Figure 2). Train foremen to supervise their workers in the use of proper lifting techniques. Make sure that two or more men are available to lift heavier trees. Provide elevators and design loading areas to minimize over-the-head lifting into field trucks or tractor trailers. Provide frequent short breaks to allow workers to relax and shift their postures.
Duration. The duration of a given task contributes to the level of risk experienced by the operator. The longer a task is performed, the greater the risk. Even when other risk factors are low, if the duration of a task is very long, injury can occur. Muscles become fatigued and injury-prone over time. Because similar forces, postures, and grips are used throughout harvest tasks, the duration of ergonomic stress is nearly continuous. For jobs that require moderate physical force levels, the ergonomic risk associated with long duration can be greatly reduced by taking one-minute mini-breaks to stretch and relax at least once every hour. If tasks are physically demanding, then more frequent and longer breaks would be needed for cardiovascular recovery, replenishing oxygen debt, and restoring water loss from sweating. Allowing workers to switch jobs throughout the day can be an effective way to provide “breaks” without losing productivity.
Relationship of Ergonomic Risk Factors. These risk factors are very dependent upon each other. A very repetitive task that is performed for a short duration with only a light application of force will not cause as much stress as a less repetitive task that is performed for a longer duration under a heavy load. For this reason it is important to consider all risk factors before assessing the overall ergonomic risk of a task. A manager must evaluate those tasks that are most likely to result in problems whether it involves heavy lifting in the loading area or repetitive hand work in the wreath-making shop.
When Injuries Occur. Encourage workers to report acute injuries immediately and any chronic pain that continues for three days or more. If a worker’s pain persists, other accommodations such as job rotation, light-duty work, longer rest breaks, medical treatments, or other interventions may become necessary. Establish medical examinations on an annual basis for tenured employees to identify developing symptoms of tingling, numbness, or poor circulation in the hand that might be related to Hand-Arm Vibration Syndrome. When either acute or chronic injuries occur try to identify their causes and adjust practices to minimize their future occurrence.
Managing Ergonomic Factors in the Workplace. Farm managers can use their knowledge of ergonomics to make the workplace safer. They can change both interior and outdoor workplaces by improving traffic flow, light levels, walking surfaces, head room, and any number of other aspects. Equipment can be altered or changed to better fit workers’ posture needs. For example, adjusting the height of work tables could reduce the need for workers to bend over. Division of tasks among workers can be planned to allow them to rest from one activity while doing something else, thus reducing fatigue-related injuries. Scheduling of different work activities and short breaks can be a vital management tool in reducing injuries. Yet, the most important way to reduce ergonomic risk factors involves employee training. Training should involve instruction on appropriate personal protective equipment, proper ergonomic work techniques and postures, and suggested warm-up exercises to strengthen back muscles and improve flexibility. Such preparation is critical to reduce the occurrence of workplace injuries, but it must also be supported by ongoing supervision with attention to safety.
Personal Protective Equipment (PPE). Provide training to all workers regarding the proper clothing and gear they should wear and use for general harvesting activity as well as for hazardous activities such as chain saw operation. Make appropriate protective gear available to workers for each activity as they engage in it, not just gear needed for their initial activity of the day. Remind workers of your expectation for them to wear the protective gear that you provide. Casual inspections might be necessary to verify that all workers are adequately equipped. It may be important to keep a record of safety training and availability of personal protective clothing and gear.
General Harvesting Clothing & Gear. While employees must be responsible for their own clothing, work conditions should be clearly explained upon hiring. If inadequately attired workers get chilled, they will not work as efficiently or as safely. Harvest workers should wear layers of sturdy warm clothing without holes or tears that might catch equipment. They should wear shoes or boots that are comfortable to stand and walk in for extended periods of time that are supportive enough for rough terrain. The soles should have adequate traction. Steel toes may not be needed for all activities, but should be considered when working around heavy equipment and objects. Good ankle support and cushioning will maximize comfort and minimize problems from ankle twisting, sprains and strains. Gloves should not be loose and should be slip-resistant when tools and equipment are involved. Cotton or cotton-blends are best. Vibration-absorbing gloves can counteract the harmful effects of extended use of vibrating tools, such as chainsaws.
PPE to use with chain saws. While chain saw accidents may be very infrequent in Christmas tree harvesting, proper PPE can make the difference between close-calls and serious injuries. Those employees who operate chain saws or lift tree branches for chain saw operators should wear the following additional protective equipment: chainsaw chaps or protective pants, hearing protection (ear muffs or plugs with a NRR rating of at least 22), eye protection (goggles or mesh screens), cut-resistant and vibration-absorbing gloves, and cut-resistant boots (ballistic nylon or leather). Hard hats are considered to be optional for Christmas tree harvest. Do not ignore the risk of chronic health problems including hearing loss and hand numbness resulting from chain saw operation. Cutting teams should switch off PPE when they switch tasks.
Christmas tree harvesting involves a wide range of ergonomic and safety concerns. Employers and employees alike need to be aware of the hazards that come not just with the use of equipment, but with the way in which people work and move. Because the nature of harvesting is a very manual process, the capabilities and limitations of human workers must be considered. Success for safety and ergonomics can be achieved by first recognizing the high-risk activities and then applying effective solutions. The following is a priority list summarizing high-risk activities along with the most effective solutions listed in the sequence of Christmas tree harvesting activities.
|Causes of Injury||Solutions to Prevent Injury|
|Lifting Heavy Loads
At every stage of Christmas tree harvesting, workers can encounter heavy lifting. The following information is critical for reducing injury during the lifting of any heavy load.
|Lifting away from body||Stand close to the object to be lifted|
|Bending over to lift item from ground||Squat to lift vertically using leg muscles, not your back|
|Lifting too heavy a load||Get enough people to help lift a heavy object|
|Starting heavy work with "tight" muscles (causing pulled or strained muscles)||Do stretching exercises before strenuous work at start of work day, after lunch, and after long breaks|
|Bending over to cut trees||Kneel down to cut trees|
|Muscle strain from pushing dull chain saw into tree trunk||Sharpen chainsaw frequently or rotate out dull chains|
|Eye injuries from tree branches, sawdust, or debris from cutting into soil and stones with excess force||Wear safety glasses or face guard|
|Operator cuts from chain saw||Wear gloves, chaps, leg guards, and steel-toed boots|
|Chainsaw cuts to person lifting branches||Person lifting branches should wear protective gear and use a longer lifting pole to increase distance from chainsaw|
|Dragging Trees to Baler|
|Straining to pull trees past obstacles (other trees)||One pull one tree if tree spacing is too close|
|Falls due to tripping over obstacles||Wear boots with treads; work in adequate light|
|Back injuries from lifting branches||Squat to lift vertically using leg muscles, not your back|
|Baling or Wrapping Trees|
|Pulled muscles pushing trees through cone||Use baler with adequately large cone for tree|
|Over-extension from reaching across to string canister||Install 2 or 3 string canisters and cutters to reduce reaching|
|Straining to catch trees that fall off baler||Let the trees fall without trying to catch them|
|Pull-through clamp springs off tree, hitting worker||Assign worker to hold pull-through clamp or buy balers with chain (no recoil) rather than cable mechanism|
|Moving Trees to or from Storage|
|Straining to lift trees onto shoulder||Squat down while keeping your back straight to center tree on shoulder and lift using leg muscles|
|Workers bump into each other||Reduce walking distance; plan foot-traffic flow|
|Forklifts or bobcats hit workers||Plan vehicle traffic flow; use beeper horns; slow down|
|Loading Trucks or Trailers with an Elevator|
|Straining to lift heavy trees||Two or more workers lift heavy trees|
|Fingers or hands entangled with elevator||Use belt conveyer and cover moving parts with guards|
|Straining back when catching falling trees||Let the trees fall without trying to catch them|
|Fall off truck or trailer||Install taller standardss, retaining ropes, and do not overload|
National Institute for Occupational Safety and Health (NIOSH). 4676 Columbia Parkway, Cincinnati, OH 45225-1998, 800-356-4674.
Publications & Videos
Simple Solutions: Ergonomics for Farm Workers. 2001. Baron, Sherry, Estill, Cheryl F., Steegle, Andrea., & Lalich, Nina (Ed.) US Department of Health and Human Services: National Institute for Occupational Safety and Health. 800-356-4674.
Easy Ergonomics, A Practical Approach for Improving the Workplace. 1999. California Department of Industrial Relations, Cal/OSHA Consultation Service. 916-574-2528
Listen to Your Body: Safe Lifting, Pushing, and Pulling, English/Spanish. 1992. 30 minutes. University of Florida. Available from: Safety Coordinator, Department of Agricultural and Biosystems Engineering, University of Arizona, PO Box 210038, Tuscon, AZ 85721-0038. 520-626-3134.
The information contained here was developed through an NC State University Extension Grant by a team of faculty from the N.C. Cooperative Extension and Industrial Extension Services. Five Christmas tree harvesting operations in western North Carolina were video-taped, observed, and evaluated for ergonomic stressors.
Publication date: Jan. 1, 2002
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