Related tests: Toluene
Clinical significance
Hippuric acid is a metabolite of toluene, produced by the liver by conjugating the amino acid glycine with benzoic acid, but it is also present in the urine of people not exposed to the solvent, as a metabolite of substances normally present in the diet (vegetables, medicines). Toluene irritates the skin and mucous membranes; it is also toxic to the central nervous system and the blood.
The amount absorbed during occupational exposure adds to the amount taken in with the diet, raising the concentration above normal values. This increase is proportional to the level of exposure to toluene.
Clinical indications
Exposure to toluene
Sample type
Urine
Preparation
A urine sample is required. It must be collected before and after the work shift.
Notes
Toluene is metabolised fairly quickly, so occupational exposure is clearly identified by comparing the urinary hippuric acid levels measured at the start and at the end of the work shift.
Cough preparations containing benzoate and psychostimulants containing para-aminobenzoate can interfere.