| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 90 === Abstract
Carbon disulfide (CS2) is widely used in many industries. Overdose exposure to CS2 can result in the damages of the neurological, reproductive, and cardiovascular systems. Thus, it becomes very important to better understand the exposure levels of CS2 among workers. Biological monitoring is less affected by other factors, which may impede the precise evaluation of the internal dose to exposure, than environmental monitoring. TTCA of 5 mg/g creatinine (Cr.) is the current biological exposure index of CS2 exposure recommended by American Conference of Governmental Industrial Hygienists (ACGIH). A great number of previous reports showed inconsistent CS2-TTCA relationship. Moreover, very limited studies involved the accumulation of repeated exposure to CS2 in the working place. The aims of this study were as follow: 1. To evaluate the difference of urinary TTCA between local and foreign workers whose work contents are different; 2. To evaluate the relations of CS2 exposure to urinary TTCA; 3. To determine the excretory half-life of CS2 in human body; 4. To evaluate the accumulation of CS2 in human body; 5. To compare the appropriateness of being biological markers of CS2 exposure between creatinine-adjusted and non-adjusted urinary TTCA. Six local workers and seven foreign workers in the spinning department were recruited as the study subjects from a rayon manufacturing factory in middle Taiwan. Airborne CS2 concentrations were monitored for each worker for 5 consecutive days. Each pre-shift and post-shift urine on each day for each worker was collected and TTCA and creatinine were measured. We found urinary TTCA concentrations were significantly larger in foreign workers than those in local workers. The excretory half-life of TTCA was found 6.58 (local workers), 7.44 (foreign workers), and 6.80hrs (total), respectively based on non- adjusted urine. For creatinine-adjusted ones, they are 7.83 (local workers), 7.97 (foreign workers), and 7.83hr (total). Significant correlation of airborne CS2 concentrations to both post-shift creatinine-adjusted urinary TTCA (r=0.48, p<0.01) and the difference of post-shift and pre-shift urinary TTCA concentrations (r=0.48, p<0.01) were found. The associations between CS2 concentrations and post-shift urinary TTCA concentration and the CS2 concentrations and the difference of post-shift and pre-shift urinary TTCA concentrations were also found (r=0.50, p<0.01; r=0.43, p<0.01) while using log-transformed data. We found the average accumulation rates for foreign workers and all workers are 0.03 and 0.02 mg/L/hr based on non-adjusted urine measurements. For creatinine-adjusted ones, the average accumulation rate is 0.02 mg/g Cr./hr for foreign workers. Based on the aforementioned findings, we propose that the accumulation of TTCA will occur while the exposure to CS2 is greater or equal than 12hrs/day and the average accumulation rates are 0.74 mg/g Cr./day and 0.43 mg/L/day. Moreover, we propose urinary TTCA of 4.86 mg/g Cr.(original data) and 4.57 mg/g Cr. (log transform data) will be found in the post-shift urine while TWA exposure equal to 10ppm CS2, very close to the current BEI settings. We also concluded that the creatinine-adjusted measurements for urine are more suitable than non-adjusted ones in the biological monitoring of CS2 occupational exposure.
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