Diethylbenzene

Endpoint summary

Description of key information

For DEB mixed isomers, limited toxicokinetic data are available only for the 1,2-DEB isomer. In mammals, 1,2-DEB is absorbed and metabolized rapidly after oral or i.v. exposure; the majority is excreted via urine or feces, after extensive enterohepatic recirculation. Systemic availability after oral is very similar to i.v. dosing indicating that 1,2 -DEB is well absorbed through the guts.

Oxidation of 1,2-DEB to the gamma-diketone 1,2-diacetylbenzene and its subsequent urinary elimination have been demonstrated. A metabolite of 1,2 -DEB is considered to be responsible for the blue coloring of tissues and fluids in rats exposed to mixed DEB. The same blueish coloring is observed with 1,2 -Diactetylbenzene indicating a common metabolite of both. This blue coloring is not considered to be an 'adverse effect'.

Although there exists data only on 1,2 -DEB, it is considered likely that the other isomers (1,3 and 1,4 -DEB) will also be well absorbed following oral administration with subsequent excretion via the bile and urine.

From the available repeated dose studies on the mixed isomers of DEB, all three isomers of DEB appear to be absorbed following inhalation exposure. Due to the high degree of bioavailability following oral exposure it is considered that inhalation and oral exposure would lead to similar levels of systemic exposure for the purposes of route to route extrapolation (where necessary).

There are no dermal toxicokinetic data available, however due to the volatility of DEB mixed isomers it is unlikely that dermal exposure will lead to significant systemic exposure given the tendency of this material to evaporate. A similar conclusion was reached for similar branched aromatic compounds such as ethylbenzene and styrene. The dermal penetration of ethylbenzene is considered to be approx 3 -4% of the applied dose, with the remainder evaporating. However the vapour pressure of DEB is approximately one third of that of ethyl benzene, and therefore DEB will persist on the skin to a greater extent compared to Ethylbenzene. Taking this into consideration it is estimated that dermal penetration of mixed DEB could be as high as 10% under unnocluded conditions. This is consistent with the observations of acute dermal and oral toxicity studies with the DEB mixed isomers where toxicity via dermal exposure was less than via oral.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential