| Summary: | 碩士 === 長榮大學 === 職業安全與衛生學系碩士班 === 105 === In order to understand the exposure profile and risk of benzene exposure for the workers in petrochemical manufacturing industries, this study aimed at the measurements of air exposure concentrations and biological markers of benzene for the workers in the petrochemical factories in a petrochemical complex area. The exposure sampling in this study adopted the comprehensive exposure assessment strategy suggested by American Industrial Hygiene Association (AIHA). Similar exposure groups (SEGs) were established for the workers in each factory. The workers in each SEG were randomly selected for benzene exposure measurements. Thermal desorption tubes packed with the adsorbent of Carbopack X were used as the sampling medium for benzene erxposure sampling by connncecting to a personal sampling pump. The measured workers were asked to provide three urine samples at the pre-shift, lunch break and post-shift times on the exposure sampling day. The collected air samples were analyzed by an automatic thermal desorption system equipped with gas chromatography (GC) system and a flame ionization detector (FID). The collected urine samples were quantified by the parent compound of benzene and its metabolites of t,t-muconic acid (t,t-MA) and S-phenylmercapturic acid (SPMA) by a headspace gas chromatography-mass spectrometry (GC/MS) system. Each worker received a data sheet for recording the work tasks he participated in each 15 minutes interval of a regular 8-hour workday during the sample collection day. The information recorded by the data sheet was coded into a data file for the analysis of exposure determinants. Twenty-one petrochemical factories (designated by A01~A21) were recruited into the study. A total of 1485 measurements of benzene exposure air samples and 464 urine samples were collected. The results of the analyses of the exposure measurement data indicated the arithmetic mean (±standard deviation) (AM±SD) of the benzene exposure concentrations of these all air samples was 4.59 (±35.56) ppb. The AMs of the exposure profiles of benzene for the SEGs in all the factories were in the range of 0.23~23.78 ppb, and the SDs were in the range of 0.28~118.53 ppb. This showed that significant variability of benzene exposure among the workers in the factories and seveal factories had the maximum measured concentrations greater than 100 ppb. In general, the benzene exposure of all the workers in the factories was less than the occupational permissible exposure limit of 1 ppm. The result of the measured concntrations of t,t-MA and SPMA in the urine samples showed there was only a low correlation (r=0.27) between the air exposure concentrations and the SPMA concentrations of the post-shift urine samples under the situation of low air benzene exposure levels. A linear regression model was built to evaluate the influence of air benzene exposure concentrations and cigarette smoking on the ratio of t,t-MA to SPMA. The result indicated the cigarette smoking had a greater influence than the air benzene exposure concentrations on the magnitude of the ratio of t,t-MA to SPMA. The cigarette smoking did result in the increase of the qunatity of t,t-MA but did not make any significant effect on the quantity of SPMA in the urine samples of the workers. Bayesian statistical analysis was used to estimate the benzene exposure risk rating for the 106 SEGs in these 21 factories. The results found 23 out of 106 SEGs had probabilities of the benzene exposure risk rating category 4 greater than 5%, and 9 out of these 23 SEGs had probabilities of the benzene exposure risk rating category 4 greater than 20%. Although the exposure measurements of the workers for the factories were in compliance with the permissible exposure limit of benzene, the focus of future exposure monitoring programs should put on the SEGs with high benzene exposure risk rating categories to protect the susceptible workers from benzene exposure and reduce the risk of benzene exposure for the workers. More exposure assessments for the workers in the high risk categories are warranted.
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