Validity of self reported occupational exposures to hand transmitted and whole body vibration

Objectives-To assess the accuracy with which workers report their exposure to occupational sources of hand transmitted (HTV) and whole body vibration (WBV). Methods-179 Workers from various jobs involving exposure to HTV or WBV comp leted a self administered questionnaire about sources of occupational expos ure to vibration in the past week. They were then observed at work over 1 h our, after which they completed a second questionnaire concerning their exp osures during this observation period. The feasibility of reported sources of exposure during the past week was examined by questioning managers and b y inspection of tools acid machines in the workplace. The accuracy of repor ted sources and durations of exposure in the 1 hour period were assessed re lative to what had been observed. Results-The feasibility of exposure in the previous week was confirmed for 97% of subjects who reported exposure to HTV, and for 93% of subjects who r eported exposure to WBV. The individual sources of exposure reported were g enerally plausible, but occupational use of cars was substantially overrepo rted, possibly because of confusion with their use in travel to and from wo rk. The accuracy of exposures reported during the observation period was ge nerally high, but some sources of HTV were confused-for example, nailing an d stapling guns reported as riveting hammers, and hammer drills not disting uished from other sorts of drill. Workers overestimated their duration of e xposure to HTV by a median factor of 2.5 (interquartile range (IQR) 1.6-5.9 ), but estimated durations of exposure were more accurate when the exposure was relatively continuous rather than for intermittent short periods. Repo rted durations of exposure to WBV were generally accurate (median ratio of reported to observed time 1.1, IQR 1.0-1.2). Conclusions-Sources of recent occupational exposure to vibration seem to be reported with reasonable accuracy but durations of exposure to HTV are sys tematically overestimated, particularly when the exposure is intermittent a nd for short periods. This raises the possibility that dose-response relati ons may have been biased in some of the studies on which exposure standards might be based, and that the levels in currently proposed standards may be too high. Future studies should pay attention to this source of error duri ng data collection.