Page 36 - Summer 2006

Standards News
MEASUREMENT AND ASSESSMENT OF WORK-RELATED HAND-TRANSMITTED VIBRATION
(ANSI S2.70–2006)
Douglas D. Reynolds
Center for Mechanical and Environmental Systems Technology University of Nevada, Las Vegas
Las Vegas, Nevada 89120
Vibration-exposed workers and hand-arm vibration syndrome
It is estimated that two to four mil-
lion workers in the US are exposed
to work-related hand-transmitted vibration. Continued habitual expo- sure to vibration directed to the hands can cause patterns of various symp- toms associated with hand-arm vibra- tion syndrome (HVAS). HAVS is a dis- ease that involves circulatory, sensory, motor, and musculoskeletal distur- bances in the hands and fingers of vibration-exposed workers. It affects the small blood vessels, nerves, and muscles of the fingers. Symptoms associated with HAVS include:
• Episodes of tingling and numbness in the fingers,
• Episodes of whitening (blanching) of one or more digits of the fingers when exposed to cold,
• Episodes of pain and cold sensations in the hands and fingers during periodic white finger attacks,
• Episodes of pain in the fingers in response to temperature changes or return of blood circulation to the hands and fingers,
• Loss of tactile discrimination in the fingers,
• Loss of manual dexterity of the hands and fingers, and
• Loss of grip strength.
In extreme cases, workers exposed to continuous high levels of hand- transmitted vibration over very long periods can experience gangrene in the digits of the fingers. Symptoms associ- ated with HAVS were first classified by the Taylor-Pelmear stage assessment (Table 1). The classification of HAVS symptoms was later refined by the Stockholm vibration syndrome classifi- cation system (Table 2). The vibration exposure time for HAVS symptoms to
first appear is called the latency period. It is determined by many factors. The most significant factors, however, are the amplitudes of the vibration energy directed into a worker’s hands and the time period in months and years over which the worker is exposed to work-related hand-transmitted vibration.
HAVS can have significant negative consequences with regard to participation
Table 1. Taylor-Pelmear stage assessment for HAVS(1)
Stage Condition of fingers Description
OO No tingling, numbness or blanching of fingers
OT Intermittent tingling
ON Intermittent numbness
OTN Intermittent tingling and numbness
1 Blanching of a fingertip with or without
tingling and/or numbness
2 Blanching of one or more fingers beyond
tips, usually during winter
3 Extensive blanching of fingers, frequent
episodes in both autumn & winter
4 Extensive blanching in most fingers,
frequent episodes in both summer
No complaints
No interference with activities No interference with activities No interference with activities No interference with activities
Possible interference with activities outside of work; no interference with work Definite interference at work, at home, and with social activities, restriction of hobbies Occupation usually changed because of severity of signs and symptoms
(1) Complications are not used in this grading
Table 2. Stockholm HAVS vibration syndrome classification system(1)
Stage Grade Description
I. Vascular Component
1 Mild
2 Moderate
3 Severe
4 Very
Occasional blanching attacks affecting tips of one or more fingers
Occasional blanching attacks affecting the distal and middle phalanges of one or more fingers
Frequent blanching attacks affecting all phalanges of most fingers
Same as 3 with trophic skin changes (tips) Severe
II. Sensorineural Component(2)
0SN Vibration exposed – no symptoms
1SN Intermittent or persistent numbness with
or without tingling
2SN Same as in 1SN with reduced sensory
perception
3SN Same as in 2SN with reduced tactile
discrimination and manipulative dexterity
(1) This system is based upon: (1) removal of the unquantifiable areas–difficulty at work, home, and hobby activities; (2) discarding of the seasonal component; (3) the Syndrome to be separated into two major areas–vascular and sensorineural; (4) separate staging of each hand.
(2) The staging is made for each hand. The final grade of the disorder is indicated by the stage and the number of affected fingers in each hand (e.g. Stage/Hand/No. of digits).
34 Acoustics Today, July 2006