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As shown in the results of the present investigation on rabbits, rats and humans (Kiese and Lenk, 1974; Engstroem, 1984), omega, p- and m-hydroxyacetophenone belong to the known metabolites of acetophenone and ethylbenzene. But the small amounts of these metabolites found in the urine would indicate to classify them as "minor metabolites". The percentage of Hydroxyacetophenone after treatment with ethylbenzene at two exposure levels was:

p-Hydroxyacetophenone:

300 ppm - 0.5%;

600 ppm - 0.7%

In the human study, ethylbenzene was rapidly metabolized and metabolites are eliminated rapidly from the body, primarily as urinary metabolites. Metabolites, such as the phenolic metabolites m- and p-hydroxyacetophenone: within a period up to 8 hrs after exposure, more than half the quantity measured in 24 hr-urine could be determined (Engstroem et al., 1984).