| Ergonomics Feature from July 1998
Issue of Industrial Safety & Hygiene News
|
REVIEWING
STANDARDS FOR |
International rules take the lead |
| By Thomas C. Jetzer, M.D., MPH, FACOEM
and Douglas D. Reynolds, Ph.D.
|
| Employee health problems caused by vibration to the hands and arms appear to be a new issue but has existed since the inception of power tools. Today, vibration is one of the most well-documented ergonomic problems, with measurability similar to noise exposure. Symptoms of vibration (called Hand/Arm Vibration Syndrome-HAVS) usually show up as a combination of finger blanching, particularly in response to cold, and progressive finger numbness. This was first defined by the Taylor-Pelmear Classification System (Table 1) and later refined by the Stockholm Vibration Syndrome Classification System (Table 2). Unlike noise exposure, it has been difficult to provide protection against vibration. Power chainsaws, the first tools to draw attention to vibration-related trauma to the upper extremity, have undergone design improvements. But percussion and other power tools have lagged behind in reducing worker exposure to vibration. |
| Table 1 Stage Assessment for Hand-arm Vibration
Syndrome(1) (Tayler-Pelmear Classification System)  |
Table 2 Stockholm (Revised) Hand-arm Vibration
Syndrome Classification System(1)  |
| Confusion with carpal tunnel In the U.S., unlike countries in Europe and Asia, we have been slow to recognize vibration trauma, and have usually confused it with carpal tunnel syndrome. Most state and federal laws do not consider hand/arm vibration syndrome, or 'white finger disease,' to be a specific entity. It certainly has not been widely recognized by the legal community, which in litigation has usually lumped the malady under the category of carpal tunnel. It's only in the past five to ten years that workers' comp suits have made vibration trauma a larger issue in the U.S. Interestingly, growing awareness of the problem in this country emerged often from product liability suits against the tool manufacturers. While there were flurries of research into vibration trauma during the '70s, no specific conclusions were drawn. NIOSH, however, did issue a Criteria Document that outlined the history of hand/arm vibration syndrome problems. In 1986, the International Standards Organization (ISO), which is comprised of member countries primarily from North America, Europe and Asia, passed ISO Standard 5349. The same year, the American National Standards Institute (ANSI) passed ANSI Standard S3.34. These standards specified procedures for measuring and quantifying vibration transmitted to the hand, and recommended guidelines for assessment and control. They implied that less vibration along with less time exposure would lead to less likelihood of developing HAVS. Not surprisingly, this caused employers to address the problem either by restricting the amount of time using the vibrating tool or switching to tools that operated with less vibration. Efforts to develop personal protective equipment as a solution to vibration have been spotty. Initially, the emphasis was on protecting the hand from cold, i.e. wearing gloves. Then a series of viscoelastic materials, basically Sorbothane and Viscolas, were used in gloves to address vibration specifically. While these gloves did provide some protection against impact and vibration in the high vibration frequencies, they provided little or no protection in the lower and middle frequencies. Also, these gloves were so bulky and/or stiff that they required extra grip exertion in order to control the tool. This is ergonomically undesirable and can actually increase other hand problems, such as carpal tunnel syndrome and tendonitis. This problem is especially true with lower quality gloves. |
| Protection standards abroad The European countries recognized quickly that the anti-vibration gloves on the market really did not meet the criteria needed for protection. On that basis, in the early 1990s, an ISO Committee working group developed ISO Standard 10819 that was adopted by all participating countries. This standard defines the performance criteria for anti-vibration gloves and puts rather stringent requirements in both mid- and high-frequency transmission for certification as an anti-vibration glove. Essentially, the standard says that at the mid frequencies, the glove cannot transmit more than 100 percent of the vibration, and at high frequencies it cannot transmit more than 60 percent. At the time, the consensus was that the standard would be difficult to meet, and people in the anti-vibration field worried whether it would ever be possible to develop personal protective equipment that could provide significant protection. The good news for the worker is that recent technological developments have resulted in new glove designs that are meeting the standard. A point of interest-and one that may change the scope of concern in this country-is the NIOSH document 97-141 on cumulative trauma and work exposure. Issued in July 1997, this document essentially defined the relationship of various musculoskeletal injuries as they relate to the workplace. It clearly states 'there is strong evidence' that the use of vibrating tools causes hand/arm vibration syndrome. Document 97-141 notes that vibration can also be a significant factor in developing carpal tunnel syndrome. In fact, in the Ergonomic Guidelines for the Meat Packing Industry, in 1991, OSHA 3123 defined vibration as a significant causative factor in upper extremity accumulative trauma. However, NIOSH 97-141 goes much further with deeper literature support. These findings are very important in that people in this country who use vibrating tools may finally have support not only for the more rare 'white finger' syndrome, but for the carpal tunnel syndrome with which the public is more familiar. There does seem to be a rising awareness that vibration is a causative problem for compensable injuries. |
| Prepare now for new standards It's estimated that in the U.S. between two and four million people are exposed to some level of hand/arm vibration on the job. It is anticipated that a proposed new ANSI ergonomic standard will address issues associated with hand-arm vibration in a more comprehensive manner. The point is, we can expect public awareness of hand/arm vibration syndrome to continue to grow here in the U.S. And American industry should prepare now to meet future standards and awareness the way overseas companies have been trying to-via decreased tool vibration or increased personal protection. |
| Thomas C. Jetzer, M.D., MPH, FACOEM of Occupational Medicine Consultants, Ltd. is a member of the USA Technical Advisory Group to ISO/TC108/SC4, Human exposure to mechanical vibration and shock. He can be reached at: (612) 280-7771.Douglas D. Reynolds, Ph.D., is professor of Mechanical Engineering at the University of Nevada, Las Vegas, NV, and chairman of the USA Technical Advisory Group to ISO/TC 108/SC4. He can be reached at: (702) 895-3807. |