A COMPARISON OF EXPOSURES TO REFRACTORY CERAMIC FIBERS OVER MULTIPLE WORK SHIFTS

As part of an ongoing, industry-wide study in the manufacture of refra ctory ceramic fibres (RCF), time weighted average (TWA) exposures have been collected at five facilities according to a standardised protoco l. Work activities were grouped into dust zones (DZs). Persons to be s ampled were randomly selected according to a protocol designed to assu re that at least one sample was collected annually from each DZ; each work shift is also sampled at least annually. TWA exposures calculated over a sampling period of at least 360 min were included in the data set. DZs were combined into one of three groups (DZGs): fibre producti on; vacuum processes; other. The data were analysed to identify any di fferences by DZG between airborne fibre exposures, by the shift worked at each facility, and across all facilities. There were no statistica lly significant shift-related differences detected between airborne fi bre exposures across the five RCF facilities when analysed as a group. Within four of the facilities, no shift-related differences were dete cted between airborne fibre exposures; however, at one facility, first and third shift exposures were statistically different. No documentat ion related to job activities was found to account for the observation . The data generally support the use of a single exposure estimate for each DZG in each of these facilities, regardless of shift worked. Res earchers reconstructing exposure and not able to determine the shift w orked by study subjects may find these results useful, but are caution ed that substantial differences in exposure across shifts may exist in other types of manufacturing. (C) 1997 Published by Elsevier Science Ltd.