Accommodating workers faced with constant vibration can be difficult: Expert
Workers who operate mobile equipment such as tractors, bulldozers, haulage trucks and even helicopters, are exposed to whole-body vibration (WBV) for the duration of their work.
One of the easiest examples of a worker who would be exposed to WBV is a backhoe operator, says Dhananjai Borwankar, a technical specialist with the Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton.
“(The backhoe) causes internal body parts to move because you’re in contact with the actual item that’s moving,” he says.
WBV is suspected to contribute to many health risks — from migraines to gastrointestinal tract problems and nausea to nervous system problems.
“Long-term exposure tends to be focused more on the spine and injuries like… scoliosis and disc problems,” Dhananjai says.
Acute problems may arise from being exposed to vibrations for a short period of time.
“Things like abdominal pain, chest pain, nausea, loss of equilibrium, shortness of breath, general discomfort — they seem to be some of the short-term issues,” he says.
Vibration has two measurable quantities, Dhananjai explains: Measuring how far the object moves, which is referred to as amplitude or intensity, and how fast the object moves, which is referred to as frequency. Combined, they create the object’s vibrational characteristics.
The speed of a vibrating object can be measured and expressed in units of metres per second or metres per second squared (m/s2).
There are generally accepted ISO standards to evaluate the health risks associated with WBV, but in Canada there is little legislation around maximum exposure, Dhananjai says.
The ISO standard measures average vibrations over an eight-hour period and caps the maximum exposure at 0.5 m/s2. Anything in excess of this has the potential for harm. If a worker is exposed to vibrations measuring 1.15 m/s2, then the worker is at serious risk for being harmed.
Marie Downey, president of ERGO, a Toronto-based ergonomics and injury prevention organization, conducted a WBV assessment with a trucking company about 10 years ago.
She rigged the trucks’ seats with accelerometers, which are commonly used to measure vibrations. She admits the assessment can be pricey.
“To set up the whole study was over $10,000 for the company,” she says, adding that not all companies have to go to that extent.
“A lot of employers don’t actually get the measure of the vibration. Instead, we can tell by qualitatively looking at it,” she says. “You know when there’s vibration — you can feel it.”
The trucking company owned two types of trucks. One type didn’t have any shock absorption in its seat, the other did. The seat with shock absorption was an air-ride seat.
“The idea with that is that it absorbs the vibration before it actually gets to the person,” she says. “That’s one of the best ways to minimize exposure.”
It’s not just the type of seating that was contributing to drivers’ health risks, she says.
“It’s how they’re sitting on the seat,” she says, noting that posture is a common contributor to body ailments.
Organizations can’t consider vibration in isolation. Scientists use the word “confounded,” Dhananjai says.
“This means there are many different factors, but you’re not sure which is contributing the most,” he says. “Best practice would be that you look at all of them.”
The worker’s environment can contribute to increased vibration, along with the condition of the machinery being used.
“Make sure that drivers know that they should have their tires at the right pressure because if they don’t it creates more bumping or jarring,” says Downey. “If they’re on a bumpy road or might be moving at high speeds across uneven surfaces, they want to try to avoid those surfaces if they can.”
At the very least, they should be trained on the right speed to suit the ground conditions, she says.
Workers that stand all day on uneven surfaces could also face problems, she says.
“We have one client and they have machinists that shake all day... The plant is on the second level, so the whole floor shakes,” Downey says. “Some people get headaches, some people feel upset to their stomach — there’s even digestion issues.”
The company is currently looking into whether it can provide matting to its workers to dampen the vibration.
If an employer is seriously looking to measure the amount of vibration its workers are exposed to, Dhananjai recommends hiring a consultant. Getting accurate measurements can be a difficult task and it may be difficult to account for everything that should be considered when determining exposure.
“You even have to be cognizant of work breaks and lunch breaks so that you assess the exposure appropriately,” he says.
Employers looking for guidance on how to accommodate its workers can turn to Alberta for assistance, says Dhananjai. The province has produced Best Practices — Vibration at the Work Site, which leverages some of the best practices established in Europe.
