Urinary metabolites excretion of turnaround process workers exposed to airborne ethylbenzene

Introduction
This study aims to investigate the relationship between the airborne level of ethylbenzene and the concentration of mandelic acid and phenylglyoxylic acid, which are urinary metabolites, during a turnaround process in styrene manufacturing factory

Methods
A total of 26 workers who participated in the turnaround process were selected as subjects. Airborne ethylbenzene was measured as a passive sampler and, for urinary metabolites analysis, the urine samples of subjects were collected twice before and after work. A questionnaire survey was also carried out on factors that affect urinary metabolites.

Results
The average concentration of ethylbenzene was 0.139 ppm for the workers. The average concentration of urinary mandelic acid was 0.069 g/g creatinine and urinary phenylglyoxylic acid was 0.028 g/g creatinine, respectively. There was a statistically significant difference between the urinary metabolites before and after work. The correlation between the concentration of airborne ethylbenzene and the concentration of urinary mandelic acid after work was significant statistically. However, factors related to work and personal habits showed no statistical significance with the level of urinary metabolites.

Discussion
The workers were exposed to low level of ethylbenzene comparing its Threshold Limit Value (20 ppm) during the turnaround process. The concentration of urinary metabolites was relatively high compare to its low airborne level. It is needed to clarify the reason of discrepancy between the airborne level and the urinary metabolites concentration. Also, a simultaneous evaluation of work environment measurement and biological monitoring is necessary considering the possibility of skin absorption of ethylbenzene during the turnaround process.