Issue



Preventing ergonomic-related injuries in laboratories


05/01/2001







SAFETY

James H. Stewart, Ph.D., C.I.H.

EFFECTIVE ENGINEERING CONTROLS CAN HELP MINIMIZE ERGONOMIC HAZARDS.

Last fall, the Occupational Safety and Health Administration (OSHA) published regulations (29CFR1910.900) for ergonomic hazards in the workplace. This standard covers approximately 100 million workers, including laboratory workers. OSHA's standard requires employers to respond to employee reports of work-related musculoskeletal disorders (MSDs) or signs and symptoms of MSDs that last seven days after they are reported.


Laboratory tasks such as pipetting, microscopy, cell counting and biological safety cabinet use are associated with ergonomic-related injuries.
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If the employer determines that the MSD, or MSD signs or symptoms, can be connected to a particular job, the employer must provide the worker with an opportunity to contact a healthcare professional and receive work restrictions, if necessary. The worker's wages and benefits must be protected for a period of time while on light duty or temporarily out of work to recover. The employer must analyze the job and, if MSD hazards are found, take steps to reduce those hazards. Employers under this standard are responsible for record keeping, job analysis and medical program planning.


NIOSH has set guidelines for the height of laboratory workbenches, fume hoods and biological safety cabinets to reduce ergonomic risk factors.
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The parts of the body involved in laboratory ergonomics-related injuries include hand, wrist, elbow, shoulder, neck and back. Laboratory tasks associated with these injuries include pipetting, microscopy, microtomy, use of biological safety cabinets and personal computers, changing centrifuge rotors, cell counting, micro-dissection and the use of flow cytometers. One study1 showed that pipetting over 300 hours per year increases the incidence of hand and shoulder injuries.

The National Institute for Occupational Safety and Health (NIOSH) found effects associated with cell plate preparation, work in biosafety cabinets and micromanipulation of small drug vials (NIOSH, HETA, 95-0294-2594).

Each year 1.8 million U.S. workers experience MSDs and about one-third of them are serious enough to require time off from work. Many MSDs are also called cumulative trauma disorders (CTDs) because they are a result of repetitive work and micro-injuries accumulating over time. CTDs include disorders of the muscles, nerves, tendons, ligaments, joints, cartilage and spinal discs.

Common ergonomic injuries
Two of the most common CTDs that affect laboratory workers include Carpal Tunnel Syndrome and DeQuervain's disease. Carpal Tunnel Syndrome is caused by chronic irritation and swelling of the tendons and tendon sheaths, causing compression of the median nerve, which runs through the carpal tunnel in the wrist.

Due to the limited size of the carpal tunnel, there is typically no room to accommodate the swelling, resulting in compression of the median nerve. Symptoms include pain, numbness, and tingling in the first three fingers and the base of the thumb. Treatment frequently includes surgery to release the pressure created in the carpal tunnel on the median nerve. DeQuervain's disease affects the tendons on the side of the wrist and at the base of the thumb. Symptoms include pain and difficulty with movement.

Other CTDs include epicondylitis, trigger finger, back injuries, wrist ganglion, thoracic outlet syndrome and tendonitis:

  • Epicondylitis is commonly referred to as "tennis elbow" and is an inflammation of the tendons within the elbow. Symptoms include swelling, pain, and weakness.
  • Trigger finger results when a tendon sheath in the finger swells and becomes locked in its sheath. The condition is referred to as trigger finger because attempts to move the finger result in a snapping and jerking movement.
  • Back injuries may result from poor posture and heavy lifting of objects such as centrifuge rotors.
  • Thoracic outlet syndrome can be caused by frequent prolonged lifting or prolonged shoulder flexion. Tasks in the lab that may result in thoracic outlet syndrome include repeated or prolonged use of long pipettes to transfer materials in a biosafety cabinet.
  • Tendonitis as a result of laboratory work is usually an inflammation of the tendons in the wrist and hand.

Characteristics of a job that increase the likelihood of ergonomic related injuries are repetition, forcefulness, awkward or static posture, contact stress and vibration. As each of these factors increases in intensity, the probability of incurring a MSD increases.

Sources of ergonomic hazards
There are a number of sources of ergonomic hazards in a laboratory environment. These are discussed below.

Microscope use. Certain tasks within the laboratory setting require significant microscope use. The traditional microscope design often forces poor posture and location of the hand controls may require significant awkward wrist angles. Many microscopes are not tall enough to permit the worker to see into the microscope objective without bending the neck forward. This results in a significant head inclination, creating stress to the neck, upper back and shoulders.

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On the other hand, when the microscope is raised to reduce the amount of head inclination, the result can be awkward wrist angles to use the hand controls. As is sometimes the case, an attempt to correct one problem (head inclination) may worsen another (awkward wrist angle).

The following controls may be helpful in reducing the ergonomic risk factors associated with microscope use:

  • Conduct an ergonomic evaluation of microscope work if an individual uses the microscope more than one hour per day.
  • Investigate ergonomically designed microscopes. These designs may include raised viewing level, allowing laboratory workers to maintain a better posture during use, and improved location and design of hand controls.
  • Consider retrofitting microscopes with adjustable eyepieces.
  • Evaluate the microscope workstation to ensure that it suits the laboratory worker's neck, arm and wrist posture.
  • Provide chairs with angled arm support, adjustable back support, adjustable height, built-in footrest and padded or curved surfaces.
  • Provide adjustable microscope stands.
  • Have lab workers take breaks and rotate tasks.
  • Evaluate the feasibility of replacing eyepieces with an electronic display.

Work area configuration. Laboratory workbenches, laboratory fume hoods, and biological safety cabinets (BSCs) are places where laboratory workers are likely to spend significant amounts of time. NIOSH has guidelines for the height of workbenches:

  • Precision work should take place at a bench above elbow height.
  • Light work should take place at a bench just below elbow height.
  • Heavy work should be conducted at a bench 4-6 inches below elbow height.

The following controls may be helpful in reducing the ergonomic risk factors associated with workbenches, laboratory fume hoods and BSCs:

  • Provide chairs with angled arm support, adjustable back support, adjustable height, built-in footrest and padded or curved surfaces. Some individuals may prefer sit/stand stools to allow switching between sitting and standing positions.
  • Footrests may also be appropriate for some individuals.
  • Consider providing padding and forearm support to reduce contact stress on the arms and wrists due to the hard edges.
  • Provide anti-fatigue mats for tasks requiring long periods of standing.
  • Plan tasks so that a worker can complete tasks easily and without significant reaching or awkward postures.
  • Select glass and plastic ware for use in BSCs that will make manipulation inside easy and will not require awkward postures, lifting at distances or other stresses.
  • Evaluate improved ergonomic hood and BSC designs. Improved models are equipped with features such as footrests, adjustable height settings and angled sashes.
  • Remove supplies and other material from bench "cut-outs" to permit comfortable seating.

Other hazards. Even though pipetting, microscope use and work-area configuration tend to present some of the most common ergonomic risk factors in laboratories, there are a number of other activities in the laboratory environment that can produce ergonomic risk factors. The table on page 34 (adapted from Chemical Health & Safety, 1998, 5(1), 20-23, 38 and the NIEHS Health and Safety Guide to Laboratory Ergonomics, 1999) lists additional laboratory tasks with possible risk factors and suggested solutions.

Ergonomic evaluations
The process of conducting an ergonomics evaluation is conceptually simple but sometimes difficult to perform well. Begin with visiting the lab and observing the way the workers accomplish their tasks. During the time in the laboratory, specifically look for the following task characteristics:

  • force
  • repetitiveness
  • awkward or static postures
  • contact stress
  • vibration

Interview some workers and ask them about tasks; how often they are performed and if they have pains or health complaints. This is a delicate process but if approached in a positive way can yield valuable insights.

The most difficult and most valuable skill to develop is hazard recognition, or identifying those tasks observed everyday that have ergonomic issues. Once an ergonomic hazard has been identified, controls need to be implemented to reduce or eliminate the hazard.

By evaluating the five factors listed above and soliciting recommendations from workers performing tasks, effective engineering controls can often be found. An effective engineering control might be replacement of a pipette with one that requires less force to operate or installation of a video display monitor on a microscope.

If effective engineering controls cannot be identified, administrative controls should be applied. An administrative control might include limiting the length of time pipetting. Whatever the solution it is important to include workers in the process. Solutions must become integrated into their work and the solution must permit, and hopefully help them, accomplish their work goals.

James H. Stewart, Ph.D., C.I.H., is director of the Health & Safety Division at Environmental Health & Engineering Inc. in Newton, MA.

References

  1. Bjorksten, M.G., Almby B., Jansson, E.S., Hand and Shoulder Ailments Among Laboratory Technicians Using Modern Plunger-Operated Pipettes, Applied Ergonomics 25:88-94, 1994.

Ergonomics defined
Ergonomics is derived from the Greek roots ergon (human work) and nomos (law or rule) and was coined by a group of scientists from backgrounds that included the physical sciences, biological sciences, and psychology. Ergonomics can be described as the science of fitting the job to the worker. When a mismatch occurs between a worker and the physical demands of the work, work-related musculoskeletal disorders (MSDs) can result.