Wz-Xylene

Both human and animal data suggest that mixed xylene, wz-xylene, o-xylene, and p-xylene all produce similar effects, although the potency with regard to a given effect may vary with individual isomers. In mice the 6-hour LC50 values for m-, 0-, andp-xylene were determined to be 5267,4595, and 3907ppm, respectively. The 4-hour LCso value for mixed xylene in rats ranged from 63 50-6700 pm. 

In all four cases, tlie initial reaction rates at the start of illumination in the continuous-feed photoreactor were higher than the pseudo-steady-state reaction rates the reaction rates declined over time until pseudo-steady-state operation was achieved. Tliis apparent deactivation phenomenon, often observed with aromatic contaminants, is discussed in Sec. III.E. In a transient reaction system, the time required to reach pseudo-steady-state operation also appears to increase in the same order as the reaction rates. For example, for the continuous photocatalytic oxidation of aromatic contaminants at 50 mg/m in a powder-layer photoreactor, the time required for pseudo-steady-state operation to be achieved was reported to be approximately 90 min for benzene, 120 min for toluene, and as long as 6 hr for wz-xylene [50,51]. Under such conditions, the difference in reaction rates between the aromatic contaminants is magnified by the fact that the more reactive aromatics retain their higher transient reaction rates for longer periods (Fig. 7). 

Raunio, H., Liira, J., Elovaara, E., Riihimaki, V. Pelkonen, O. (1990) Cytochrome P450 isozyme induction by methyl ethyl ketone and wz-xylene in rat liver. Toxicol, appl. Pharmacol., 103, 175-179... 

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