Hand-arm vibration syndrome
Workers who use power tools may be at risk
- About 2 million U.S. workers are exposed to hand-arm vibration, and as many as half will develop HAVS, one expert says.
- Hand-arm vibration affects various industries, including construction, mining and forestry.
- Preventive measures can help workers limit hand-arm vibration.
In 1918, occupational physician Alice Hamilton traveled to Bedford, IN, to study limestone quarry workers.
Stonecutters in Bedford who used air hammers during work shifts had reported experiencing numbness and discoloration of their fingers.
Among 38 stonecutters, Hamilton found that 89 percent reported “vibration-induced white finger,” according to research published in the British Journal of Industrial Medicine. Fast-forward to modern times, and the disorder is known as hand-arm vibration syndrome. Symptoms range from tingling, numbness, pain and “blanching” (loss of color) in the fingers, as well as weakened grip due to nerve and blood vessel damage, from using vibrating tools. In severe cases, gangrene can occur.
About 2 million U.S. workers are exposed to hand-arm vibration, and as many as half will develop HAVS, according to Frederick, MD-based occupational vibration consultant Donald Wasserman. Some experts believe the number may be higher because the disorder is sometimes unrecognized or underreported – and is sometimes confused with carpal tunnel syndrome.
“I’d go as far to say it’s probably the No. 1 neuromuscular disorder in the world in manufacturing and construction environments, the most costly, and underappreciated,” said Donald Peterson, dean of the College of Science, Technology, Engineering and Mathematics at Texas A&M University-Texarkana.
Who’s at risk?
Workers who regularly use power tools in various industries – from construction and maintenance to mining and forestry – are at risk, as well as workers in colder climates.
Any kind of vibrating tool can result in hand-arm vibration, and longer exposure can increase the risk of developing HAVS, experts say.
Tools that have been linked to hand-arm vibration include:
- Chain saws
These tools can cause hand-arm vibration regardless of whether their power source is electricity, gasoline or air, Wasserman said.
Hand-arm vibration syndrome can take six months to six years to develop and, after the fingers blanch, the condition is irreversible, according to NIOSH biomechanical engineer Daniel Welcome. Therefore, prevention is crucial.
“The whole thing boils down to prevention,” Wasserman said. “If you don’t catch it early enough – either stop the exposure, get that person out, change their job, do something else – it’s going to go from bad to worse.”
How can workers be protected?
Experts advise the use of anti- or low-vibration tools that are appropriate for the job. David Rempel, professor of bioengineering at the University of California, Berkeley, recommends employers purchase tools with lower handle vibration and reduce the hours of exposure per day.
Other measures also can help. Wasserman and colleagues identified eight “good work practices,” originally shared in the American Society of Safety Engineers’ Professional Safety journal:
- Keep the hands warm.
- Refrain from smoking.
- Grip the tool as lightly as possible.
- Keep the tool well-maintained.
- Keep cold exhaust air from pneumatic tools away from the hands.
- Take breaks from working with tools – rest for at least 10 minutes per hour.
- Use gloves that cover the fingers and are certified by ISO 10819.
- Seek medical attention if HAVS symptoms appear.
“One of the simplest work practices is holding the tool with only the amount of force that’s required to keep it safely under control,” said Mark Geiger, occupational safety and health manager with the Washington-based Naval Safety Center Liaison Office. “People who grip a tool with a death grip increase the vibration coupling. They also fatigue themselves more quickly.”
OSHA offers the following possible solutions for avoiding HAVS:
- Damping techniques or using vibration isolators on equipment provide the most effective protection.
- Keep machines in proper working order.
- Alternate between using vibrating and non-vibrating tools.
- Limit the number of hours a worker uses a vibrating tool. Let workers take 10- to 15-minute breaks every hour.
- Train workers about vibration hazards, including information about sources of vibration exposure, early signs and symptoms of HAVS, and work practices for limiting exposure.
- Instruct workers to keep their hands dry and warm, and to grip the tool lightly.
A Defense Safety Oversight Council project has tried to improve the federal supply of low-vibration hand tools and protective equipment in federal shipyards. The General Services Administration now considers vibration when choosing and marketing power hand tools, Geiger said. About 130 such tools are available in the federal supply system. Outreach in the Department of Defense has increased awareness of HAVS, he added.
What about gloves?
The use of anti-vibration gloves is controversial, according to Geiger.
A NIOSH study tested four types of gloves using medium- to high-frequency tools such as saws and grinders, and found that gloves lowered vibration to the palm 5 percent to 20 percent. Yet some gloves slightly increased or slightly decreased vibration with low-frequency tools.
Gloves are more effective at reducing vibration in the palm than the fingers because the palm absorbs vibration, Welcome said. Fingers may amplify vibration with a frequency of 100-300 hertz with or without gloves.
A worker will receive little benefit from anti-vibration gloves for a frequency under 25 hertz, he said, but noted that gloves are still effective at keeping the hands warm and protecting against cuts, abrasions and other exposures. Anti-vibration gloves also can be useful for holding a vibrating tool, such as a jackhammer, in place and allowing it to do the work.
Make sure the gloves have been tested by a third party and meet ANSI 2.73/ISO 10819 standards, which require the full hand to be covered, Geiger said. Similar to other protective equipment, gloves are the least preferred control measure.
“Reducing the [vibration source] is the most important thing one can do,” Geiger said. “But anti-vibration gloves are useful for a couple reasons. They keep the hands warm. They do reduce some shock. Anybody buying anti-vibration gloves has a partial solution and needs to be aware that, as protective equipment, they have intrinsic limitations.”
Wasserman stressed the importance of wearing ISO 10819-certified, full-finger gloves because HAVS starts in the fingertips rather than the palms of the hand.
“Many people, when they buy a full-fingered glove, don’t feel like they’re getting enough tactile feedback into the fingertips. They’ll cut the fingers off, leave only the palm area. Do not do that,” Wasserman said. “You might as well not have a glove on if you’re going to cut the fingers off.”