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Employees who regularly drive forklifts, trucks, buses, tractors, and heavy equipment or who stand where the floor is vibrating from heavy machinery may be exposed to the damaging effects of whole-body vibration (WBV). Affecting over 6 million U.S. workers, WBV has been linked to a variety of low back disorders. WBV can also affect vision, and cause fatigue and motion sickness.
WBV is transmitted through the thighs and buttocks to the entire body from a vehicle seat or through the feet and legs from a vibrating floor. The risk of injury depends on the magnitude, frequency, and direction of the vibration, as well as the duration of exposure. Vehicles often vibrate at a frequency where human resonance occurs (4-8 Hertz), which means the body amplifies the vibration, making it particularly hazardous.
National and international organizations – the American National Standards Institute (ANSI), the International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH) – have developed standards and threshold limit values (TLVs) for measuring and quantifying vibration. The standards are fairly complex and companies wishing to measure vibration levels would be advised to seek the assistance of a vibration expert. Alternatively, the simplest and safest thing to do is to assume that workers are at risk if they regularly operate vehicles and machinery for most of their workday.
Listed below are possible engineering and administrative controls that help to reduce worker exposure to WBV:
- Equip vehicles with Air-Ride seats, which, in addition to reducing vibration, typically offer more adjustability and support than standard seats.
- Purchase or retrofit vehicles with suspension systems that minimize vibration.
- Purchase or retrofit vehicles with mechanically isolated “floating” cabs.
- Use good work practices, such as taking periodic rest breaks for every 1-2 hours of continuous exposure, not lifting objects immediately after prolonged WBV exposure, and exiting the vehicle using the 3-point dismount versus jumping.
- Choose appropriate speed for the terrain, and avoid potholes, ruts, and bumps as much as possible.
- Ensure that company owned roads, parking lots, and floors are well maintained and free of debris and damage as smoother surfaces reduce vibration.
- Ensure that vehicle suspension systems and tire inflation are properly maintained.
- Add isolators (bushings) under machinery to reduce the transmission of vibration to the floor.
- Remove the operator from the machine via remote controls.
- Incorporate shock mount stand plates and vibration damped controls in the design or purchase phase.
- For standing work, provide anti-fatigue mats under the feet to dampen vibration.
Air-Ride seat manufacturers include:
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