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665275 
Journal Article 
Effect of Fasting on Toluene Metabolism: A Study of Hippuric Acid and o-Cresol Excretion 
Ong, CN; Foo, SC; Lee, BL 
1994 
Yes 
Applied Occupational and Environmental Hygiene
ISSN: 1047-322X
EISSN: 1521-0898 
9 
9 
622-625 
A study was performed to examine the relationship between toluene (108883) concentration in the breathing zone air and concentrations of urinary hippuric-acid (495692) (HA) and o-cresol (95487) (OC), and to determine whether abstinence from water and food may affect the metabolism of toluene. The study participants included 34 healthy workers in two plastic bag printing factories. Although respirators were provided for the workers, none of them were seen using the devices during the study period. Fifteen of the workers agreed to participate in an identical study during the Islamic month of Ramadan when no food or water was taken from sunrise to sunset. Worker exposure to toluene was measured by personal air samplers, and analysis was performed by gas chromatography (GC). Urine samples were obtained from the subjects and subjected to high performance liquid chromatography for the analysis of HA. The concentration of urinary OC was determined by acid hydrolysis, diethyl-ether extraction, and analyzed by GC. The workers were exposed to toluene in concentrations up to 200 parts per million (ppm) during their 8 hour shifts from Monday to Saturday. A strong correlation was seen for breathing zone toluene and urinary HA. The relationship between environmental toluene and urinary OC was also observed. The fasting study group excreted significantly less HA at the end of the shift than on normal workdays. In contrast, the excretion of OC was much higher during the fasting days, with an estimated excretion of 1.17 milligram/gram (mg/g) creatinine at 50ppm toluene exposure as compared with 1.09mg/g creatinine. The authors conclude that dietary intake may affect toluene metabolism and should be considered when using toluene metabolites for the biological monitoring of exposure.