Effect of Soft Drink on Urinary Hippuric Acid Excretion in Workers Exposed to Low dose Toluene

Lee, Yong Jin

Abstract

OBJECTIVES
To investigate the effect of soft drink containing benzoic acid on the excretion of urinary hippuric acid after ingestion of soft drink containing benzoic acid before working (Edthe deleted section is not an objective).
METHODS
Fifty workers (male, 35; female, 15) exposed to toluene in Choongchung province area were studied. Urinary samples were collected on two days. On the first day, all study subjects were required to avoid any soft drink containing benzoic acid for the 24-hour period before urine collection. After emptying their bladder before starting work, the total volume of urine for the full shift period was collected and spot urine was collected at the end of the shift. On the second day, all workers were provided with soft drink containing benzoic acid before the shift and the same urine collection procedure was applied as on the first day. The air concentrations of toluene for each workers was measured with personal air sampling with 3M organic solvent badge. Personal informations such as age, sex, smoking and drinking habit were collected by self-administered questionnaire method.
RESULTS
The geometric mean of urinary hippuric acid without ingestion of soft drink containing benzoic acid was 0.49+/-0.45 g/g creatinine in total volume urine, and 0.51+/-0.53 g/g creatinine in spot urine, whereas the equivalent results with ingestion of soft drink were increased to 0.92+/-0.61 g/g and 0.96+/-0.78 g/g, respectively. Stepwise multiple regression of urinary hippuric acid with air concentration of toluene, benzoic acid and other covariates revealed that 49% and 11% of urinary hippuric acid concentration in total volume urine analysis were attributed to the air concentration of toluene and benzoic acid, respectively, compared to 45% and 6% in spot urine analysis, respectively. On the other hand, taking the difference of urinary hippuric acid before and after ingestion of soft drink containing benzoic acid as a dependent variable and taking the air concentration of toluene, benzoic acid and other covariates as independent variables, stepwise multiple regression analysis revealed that 14% and 13% of urinary hippuric acid concentration in total volume urine analysis were attributed to the air concentration of toluene and benzoic acid, respectively, whereas only 9% of urinary hippuric acid concentration in spot urine analysis was attributed to the air concentration of toluene, (Ed- note that there is no respective comparison here).
CONCLUSION
Soft drink containing benzoic acid significantly affected the level of urinary hippuric acid after ingestion of soft drink before working. It is recommended that for the accurate elevation of urinary hippuric acid as an index of toluene exposure, detailed information on soft drink containing benzoic acid needs to be checked in the process of the health examination of toluene exposure workers.