Civil Engineering Reference
In-Depth Information
For the right hand of the thigh boner, the acceptable finger force is
Peak finger force
7
:
77
0
:
77
6
Peak finger force
3
:
1
Since the observed force was four, the TLV is clearly exceeded by the right hand. In addition to the force
and posture, it can be seen from Figure 41.3(a) and Figure 41.3(e) that there is also repeated wrist flexion
and deviation. Engineering controls need to be considered to reduce the finger forces and the postural
stresses on the wrist. Administrative controls also should be implemented as long as the peak finger
force and HAL values are near the action limit.
Similarly, the TLV is not exceeded by the left hand, but was slightly above the action limit.
TLV
Peak finger force
7.77 - 0.77
5
Peak finger force
3.8
Action limit:
Peak finger force
5.55 - 0.55
5
Peak finger force
2.8
This example was based on the average strength of a female in her early 40s. Different results would be
obtained for workers with different strengths. It is important that strength values representative of all of
the workers be considered — male-female, young-old, and lower percentiles in each category.
Administrative controls should be continued as long as exposures are close to the action limit. Admin-
istrative controls should include educating workers about the symptoms of hand-wrist-forearm MSDs
and where to go to get help if symptoms occur. Workers also should be instructed in best work practices,
and how to adjust their equipment. Supervisors should be instructed about the symptoms of MSDs, best
work practices, and work station setup so that they can assist workers. Controls should include surveil-
lance of worker symptoms, injuries, and illnesses to identify both reported and unreported problems so
that appropriate interventions can be implemented. Surveillance should include further analysis of the
job to identify causes for high forces and posture stresses so that they can be addressed. Finally, there
should be some kind of administrative structure to manage these control efforts, for example, an
ergonomics team or safety committee.
41.7 Summary
The ACGIH TLV is a tool for assessing the risk of hand-wrist-forearmMSDs. The TLVapplies to mono-
task hand work performed for four or more hours per day. The TLV considers HAL and peak finger force,
but recommends that other work factors, such as wrist posture, contact stresses, and hand-arm
vibration, also be considered — particularly when exposures are close to the TLV. Also, workers
should be advised to discuss personal factors, such as weight, chronic diseases, pregnancy, and past inju-
ries, with their health-care provider. Peak finger force and HAL can be determined from observations or
calculated from time-based measurements. Time-based measurements may be obtained from sequential
analysis of video recordings or electronically from electromyography, force gauges, and goniometry.
Exceeding the TLV should initiate an engineering control change process. Those jobs exceeding the
action limit should have administrative or engineering controls applied.
References
ACGIH (2005a). Documentation of the TLVs and BEI with Other Worldwide Occupational Exposure Values
2005. Cincinnati, OH: ACGIH Worldwide.
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