Exposure to vibration: Do you know the limit?
Exposure to vibration: Do you know the limit?
According to the Naval Safety Center, two million workers in the United States are affected by Hand-Arm Vibration Syndrome (HAVS) caused by regular use of powered-hand tools at work. Though one of the less obvious occupational hazards, continued vibration exposure can potentially lead to irreversible nerve, blood vessel, and muscle damage, and the possible risk of Carpal Tunnel Syndrome (CTS).
Workers who regularly use handheld or hand-guided power tools and machines—including grinders, concrete breakers, hammer drills, chainsaws, hedge trimmers, powered mowers, and cutting tools—are at risk of developing HAVS.
Tingling and numbness in the fingers, lack of feeling, and loss of strength are early signs and symptoms to look out for, particularly if hammer action tools are utilized for more than 15 minutes per day, or rotary action tools for more than one hour a day. The main health issues as the result of vibration exposure are divided into three subgroups:
Vibration White Finger (VWF), or Raynaud’s Disease, a vascular disorder caused by restricted blood flow that results in visible blanching of the hands.
Neurological Vibration (Carpal Tunnel Syndrome), which causes tingling and numbness in the fingers, resulting in a lack of dexterity.
Muscle and soft tissue damage, including conditions such as arthritis, changes to muscles, and tendonitis, which can result in loss of grip strength.
The continued use of high-vibration tools will likely worsen symptoms, resulting in irreparable damage. For instance, affected workers could experience permanent numbness in the hands and increased difficulty in grasping smaller objects. Cold temperatures and smoking can also worsen symptoms.
HAVS is preventable, but once the damage is done, it is irreversible. Understanding and controlling the potential exposures created by tools and machinery is crucial to safeguard workers.
Employers should look for work methods that eliminate or reduce exposure to vibration. One area of importance to consider is equipment selection. Ensuring that the equipment intended for a specific task is suitable will help to improve efficiency and keep the worker from harm.
Though it’s good for workers to utilize tools with the lowest vibration suitable for a task, if equipment is not powerful enough it may expose employees to vibration for longer than is necessary. Limiting the time that workers use powered tools and are exposed to vibration is also advisable. Planning work schedules to avoid long, continuous periods of tasks that involve vibration can further reduce the risk of developing HAVS. Numerous shorter periods are preferable.
Providing workers with quality protective clothing, keeping them warm and dry at work, will encourage good blood circulation and help alleviate conditions associated with HAVS. Equipping employees with gloves to keep hands warm can also protect from VWF; however, experts warn that gloves should not be relied upon to provide protection from vibration—especially gloves marketed as “anti-vibration” gloves. These are only suitable for certain tasks and are not particularly effective at reducing the risks of HAVS, actually increasing the vibration at some frequencies.
Vibration exposure monitoring
OSHA does not have standards concerning vibration exposure, though together with ACGIH the agency recommends conforming to Threshold Limit Value guidelines. Developed by ACGIH, TLVs are believed to be the level of exposure most workers can experience for a working lifetime without adverse health effects.
To best prepare workers, employers should ensure that powered tools or machinery utilized at work are safe to use, as indicated by its level of vibration. Hammer drills, for example, typically operate at 9 meters per second squared (m/s2). The TLV for vibration is 5 m/s2 as an eight-hour time-weighted average.
To avoid companies and workers suffering the harmful effects of vibration, employers should also conduct regular vibration risk assessments of the workplace. This allows employers to determine the degree of vibration exposure and focus on practical steps to reduce the risks.
The data from monitoring enables employers to calculate the vibration risks their work force may face, either all of the time or on an intermittent basis. Close observations of the work force will ensure ill-health problems are detected.
If worker exposure is regularly reaching values beyond recommended limits, employers have a duty to consider whether the work could be done in a different way. Sustained exposure levels to just below the limits still leaves workers at risk of developing the condition.
Tim Turney, Technical Product Manager Casella
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This article was first published in the AIHA online magazine