Many industrial processes are using hand -held vibratory
tools and grinding operations in which there is increasing
vibration energy entering the hands and arms of operators. The
vibration stimulus causes digital artery changes giving rise
to Raynaud's Phenomenon of Occupational Origin.
The serious nature of this hazard came to the author's
attention in chain saw,, forestry workers around 1965 -68 when
the saw usage time, and therefore the vibration exposure time,
increased from 1 -1z hours to 52 -6 hours per day for 5 days per
week, resulting in a prevalence of vibration -induced white
finger (VWF) of over 90% in one forest in Norfolk.
From 1968 to 1976, the period covered by this Thesis, an
epidemiological study of 18 work situations (1283 vibration
exposed subjects and controls) has been carried out to define
the extent of VWF in industry and to assess its severity. At
the same time a team of physicists and engineers measured the
vibration characteristics of these work processes, the object
being to relate the prevalence rates of VWF, the latent intervals
(time interval between vibration exposure and the appearance of
the first white finger tip), and Stage assessments (severity) to
the vibration spectra, thus establishing damage risk criteria.
With the help of this survey data, as opposed to limits obtained
from subjective comfort responses, a British Standard Draft
Proposal (1975) for hand -arm vibration has been issued mainly
to act as a guide to hand -held vibratory tool manufacturers and
to prevent the complications of VWF such as finger tip tissue
necrosis from arising following long -term vibration exposure.
A suggested Code of Practice is described. The difficult
question whether to accept Raynaud's phenomenon of occupational
origin as a Prescribed Disease is discussed.
Raynaud's phenomenon arising from chain saw operation has
not been reported since anti -vibration treatment of the chain
saw introduced by Forestry Commission in 1970. No new case of
VWF has been found after six years of A/V saw usage. On the
other hand pneumatic tool users still constitute a high risk
VWF area despite the fairly long latent interval (6 -7 years
compared with 2 -3 years for chain saws). Measurement of vibration and the energy entering the hands of pneumatic tool
operators (grip force) have proved difficult both from the
instrumentation (destruction of accelerometers) and standardisation of method. Further medical surveys of pneumatic tool
operators with measurement of the vibration characteristics
of these percussive tools are required to establish scientifically based damage risk criteria. Such work is being actively
pursued in Britain (Universities of Dundee and Salford) and
surveys are being planned with the author for chippers and
grinders using pneumatic tools in foundries in the United
States of America.
Despite considerable efforts to find an objective test
which would establish the diagnosis of Raynaud's phenomenon
and its degree of severity other than by the subject's own
description of VWF attacks, no single reliable field test has
been devised on an individual basis. All the established
tests quoted in the literature, heating and cooling of the
digits, plathysmography, vibro- tactile threshold levels and
neurological tests (light touch, pain and temperature) - will
differentiate, at a significant level, differences between
vibration exposed populations and controls. All fail, however,
on an individual basis. The long term solution lies in
prospective surveys as opposed to the retrospective surveys
described in this Thesis.