Occupational disease caused by vibration in the workplace can be insidious for those who experience it, but there are ways to mitigate its impact on workers.
Katie Goggins, a senior scientist with the Centre for Research in Occupational Safety and Health (CROSH) in Sudbury, studies the impact of vibration on humans in the workplace.
She was the inaugural keynote speaker as part of the Leo Gerard Legacy Fund Lecture Series during the annual online CROSHCon virtual research symposium held on Jan. 19.
Named for Sudburian Leo Gerard, the series pays tribute to his contributions to workplace health and safety, both as a former president of the United Steelworkers union and as a founding member of the CROSH advisory board.
When it comes to workplace-exposed vibration, humans can be exposed in multiple ways, Goggins noted: from a seated position as a mobile equipment operator, as an operator holding a vibrating tool, and as the operator standing on a vibrating platform.
“Vibration is actually a form of mechanical wave that oscillates about a fixed point,” she said. “It's kind of like noise in this way. They're both waveforms. Vibration can enter the body through any point that's in contact with the vibrating surface.”
Goggins said researchers typically measure the impact of vibration by examining the duration of exposure, the magnitude of the bounce, the frequency of the bounce, and its direction.
But it can be difficult to measure when a worker is exposed in all three ways at once.
For a forklift operator, for example, vibration is transmitted to their hands through the steering wheel, to their feet through the pedals and floor of the machine, and to their buttocks through the seat.
The health impacts can be numerous.
For a seated operator, short-term impacts include muscle fatigue, distorted motor performance, headaches, dizziness or motion sickness. They could even experience elevated heart and respiratory rates, decreased cognitive function, and impaired speech and vision.
Longer term, they could experience lower back, shoulder and neck pain, spinal degeneration, hearing loss, and even a greater risk of prostate cancer, Goggins said.
“Ultimately, there's a lot of research finding that seated operators exposed to whole body vibration are at an increased risk of musculoskeletal disorders, with the neck, shoulder, lower back, wrist and hand and knee pain being possible,” she said.
“One thing we do know is that lower back injury risk increases when whole body vibration exposure is combined with non-neutral postures, or rotated or twisted postures.”
Ideally, the best solution to the issue is to replace heavy duty equipment with mobile-operated equipment.
Where that’s not possible, companies should make adjustments to decrease exposure to whole body vibrations, she said.
Seats can be installed that reduce vibration transmission to mobile equipment operators, she noted, and companies could even institute road maintenance programs to smooth out the surfaces drivers travel often.
Workers should take frequent breaks as well.
“Setting workplace speed limits is really important,” she added. “Operators do tend to travel faster when the equipment is unloaded. But this can actually cause larger jolts to the equipment if travelling on the same train when compared to a loaded vehicle.”
Heavy equipment operators rarely receive training about how to set their seat suspension correctly, she noted, but CROSH is currently developing a seat testing training module for heavy equipment operators in collaboration with a local mining company.
“If we started treating this like office ergonomics where the worker gets a full training on how to adjust all the components of their workstation, it could result in better postures and more effective use of the seat suspension for attenuating vibration for our workers,” she said.
Workers exposed to vibration while holding tools are most commonly prone to developing carpal tunnel syndrome, which is one of the top two most common occupational diseases in mining, forestry, pulp and paper, Goggins noted.
It’s characterized by numbness and tingling in the hand, resulting in a reduced sense of touch or temperature.
Workers may also develop white finger syndrome, which causes their fingers to periodically and temporarily turn white, or tendonitis, which is the inflammation of tendons, and can result in reduced hand strength and manual dexterity.
In general, Goggins said, the longer a worker uses a piece of equipment that causes vibration, the more likely they are to develop injury from vibration.
“This really means we need to be careful with how long we let workers operate this equipment,” she said.
As with the heavy machinery, workers need to use handheld equipment that reduces the amount of vibration transmitted.
In one case study, welders and metal fabricators were given low-vibration angle grinders, which dramatically reduced the amount of vibration they were exposed to, Goggins said.
The tradeoff, she said, is that the new equipment cost about $1,000 more than the traditional equipment, it took a month to develop new standard operating procedures associated with the equipment, and alterations had to be made to the air distribution systems.
Goggins suggested employers should choose ergonomic work equipment and workspaces, and equipment should be maintained regularly.
“Limiting the duration and magnitude of exposure as much as possible with break scheduling or job rotation, health and medical surveillance, and protecting the employees from cold and damp conditions is imperative, too, because our body will already start the vasoconstriction of the arteries in the periphery or the hands and feet in cold conditions,” Goggins said.
Symptoms of foot-transmitted vibration exposure — Goggins’ specialty — mimic those of hand-transmitted vibration exposure.
First symptoms are numbness and tingling in the toes, and a reduced sense of touch or temperature.
The skin on the feet or toes can turn white initially, then to blue or purple before shifting to red.
“This kind of vascular damage and loss of circulation can occur in as little as two to three months of prolonged exposure to vibration,” Goggins said. “So without intervention, the damage can be permanent and necrosis or tissue death can occur.”
Bone and joint damage, or muscular fatigue of the lower limb can also occur.
Unfortunately, Goggins said, attempts to reduce workers’ exposure to hand-transmitted vibration have actually created the exposure to foot-transmitted vibration.
“So, by taking vibrating tools out of the hands of underground workers, and instead creating equipment that we stand on to operate, the contact points associated with occupational exposure to vibration have changed,” she said.
By far, Goggins said, foot-transmitted vibration is the least studied of the three worker vibration exposures, and her work will continue in this area.