Differences in urinary monochlorobenzene metabolites between rats and humans.

Differences in urinary excretion of monochlorobenzene between rats and humans were studied. Monochlorobenzene was administered to rats and humans intraperitoneally, orally or by inhalation. Urinary p-chlorophenylmercapturic acid and 4-chlorocatechol, after hydrolysis of its conjugate, were measured. The excretion of p-chlorophenylmercapturic acid was somewhat more than that of 4-chlorocatechol in rats which were administered monochlorobenzene orally or intraperitoneally. The excretion of p-chlorophenylmercapturic acid was markedly less than that of 4-chlorocatechol in humans who received monochlorobenzene orally or by inhalation. The results indicate that the 4-chlorocatechol conjugate is a suitable index of metabolites in the urine of workers exposed to monochlorobenzene.