Differences in urinary monochlorobenzene metabolites between rats and humans

Area of Science:

• Toxicology
• Environmental Health
• Biochemistry

Background:

• Monochlorobenzene (MCB) is an industrial solvent with potential health risks.
• Understanding MCB metabolism and excretion is crucial for occupational health monitoring.
• Species-specific differences in xenobiotic metabolism can impact biomarker selection.

Purpose of the Study:

• To investigate and compare the urinary excretion patterns of monochlorobenzene metabolites in rats and humans.
• To identify a suitable urinary biomarker for assessing occupational exposure to monochlorobenzene.

Main Methods:

• MCB was administered to rats and humans via intraperitoneal, oral, and inhalation routes.
• Urinary levels of p-chlorophenylmercapturic acid and 4-chlorocatechol (after hydrolysis) were quantified.
• Metabolite excretion profiles were compared between species and administration routes.

Main Results:

• In rats, p-chlorophenylmercapturic acid excretion exceeded 4-chlorocatechol excretion after oral or intraperitoneal MCB administration.
• In humans, p-chlorophenylmercapturic acid excretion was significantly lower than 4-chlorocatechol excretion following oral or inhalation MCB exposure.
• A clear distinction in metabolite profiles was observed between rats and humans.

Conclusions:

• Urinary 4-chlorocatechol is a more suitable biomarker for monitoring monochlorobenzene exposure in humans than p-chlorophenylmercapturic acid.
• Species differences in MCB metabolism necessitate careful consideration when extrapolating toxicological data and selecting biomarkers.
• The findings support the use of 4-chlorocatechol as an effective index for workers exposed to monochlorobenzene.