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Abstract
OBJECTIVES
This study was conducted to assess the concentration of xylene exposure and exposure variability of a similar exposure group(SEG) in accordance with job title and confined space.
METHOD
The study subjects included 28 workers working in the painting process in the ship-building industry. Measurement of subjects were repeated three times. Within and between-worker exposure variance components were estimated from log-transformed exposure concentrations employing a one-way nested random effects analysis of variance model. A uniformly exposed group was defined as one where the between-worker variance(sigmaB2) was less than or equal to 0.031 or bwR95 <or=2, where b wR9 5 =exp(3.92 bwSy), representing the ratio of the mean exposures of the 97.5th and 2.5th percentile groups of the workers sampled.
RESULT
The results indicated that, contrary to popular belief, similar exposed groups based on job title were heterogeneous. The between-worker variance(sigmaB 2) is large(>or=0.031) and the ratios of the 97.5th and 2.5th percentile workers of the log normally distributed exposures of each group of workers was more than 2. However dividing job title into confined space(in-block, out-block, in/out-block) decreased the between-worker exposure variability.
CONCLUSION
This study focused on the quantitative aspects of exposure in painters in the ship-building industry. We cannot accept the assumption that SEG are uniformly exposed, as a major component of variation in exposure relates to differences in tasks or other factors. Therefore, the observational schemes can be improved by investigating jobspecific task and practice.
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