Limit of 24 minutes for chipping rust, and 27 minutes for angle grinders. The risk of permanent injury increases after these time periods. Hans Pettersson, who works with noise and vibration at Umeå University, explained the figures.
Vibration is now the most common cause of occupational injury among workers insured through AFA. People affected are in all age groups, but many are injured early in their working lives.
“A lot of people just don’t know how quickly vibration injuries are caused,” says Hans Pettersson, PhD in work environment medicine, who was another of the speakers at the SAN conference. Some are affected as early as in their 20s.
At sea it is particularly hand-held vibrating tools that cause problems in the form of injuries to nerves and blood vessels. White fingers and numbness are two of the most common symptoms, and for those who are affected there is no cure. It is very important that an injured person stops using vibrating tools immediately.
“If you have minor vascular injuries they may improve slightly if you stop that type of work, even though they will never heal completely. More serious vascular and nerve injuries can’t be reversed, but there is a large risk that they will get worse if the exposure continues,” says Hans Pettersson.
In order to reduce the risk of vibration injuries, people must stay within limits. When working with standard chipping hammers, the limit is 24 minutes a day; for a percussion drill it is 20 minutes and for tiger saws as little as 9 minutes.
“If a number of hours of rust chipping are needed during one day, the only solution is job rotation. Anti-vibration gloves on the market are just not good enough for us to recommend them,” says Hans Pettersson.
The tool may also vibrate more than the manufacturer claims, shortening the safe time for their use. When vibration levels were checked for nine different tools, higher values than those stated were measured in five of them.
“The amount of vibration can vary between different users, and old tools vibrate more than new ones. A chipping hammer used a few hours a day needs to be replaced after only six to twelve months due to wear, though the length of time varies between different makes,” says Hans Pettersson.
Vibration damage can also increase the risk of hearing injuries. When Hans Pettersson was writing his thesis, he noticed how people suffering from white fingers also had an increased risk of hearing loss.
“White fingers causes less blood circulation, which can reduce the blood supply to the cochlea. It’s possible that this increases the sensitivity of the ear,” he says.
According to a questionnaire on the work environment at sea published by Sahlgrenska University Hospital a couple of years ago, 89% of engine room crew and just over 50% of deck and service personnel were exposed to high levels of noise. Of these, 85% used hearing protection.
“High noise levels are harmful and it makes no difference whether it is sound we enjoy, such as music, or industrial noise from tools and machines,” says Hans Pettersson.
Immediate hearing injury
Injuries from noise can occur very quickly. Short, loud sounds can burst hearing cells and cause immediate hearing injury. The most common result of long-term exposure to noise is hearing loss or tinnitus.
“There are limits for noise levels in the workplace and it’s possible to take measurements. But as a rule of thumb, if you need to shout when you’re talking to someone a metre away, the sound level is harmful,” says Hans Pettersson.
Linda Sundgren, text and photo