Xylene (dimethyl benzene) is a mixture of the three isomers plus ethylbenzene
(6-15%) and occasionally toluene, trimethyl benzene and other trace components.
It is widely used as a solvent and thinner for paints and varnishes, often in
combination with other organic compounds and as a solvent in glues, printing
inks, and fat solvent in microscopy.
Xylene is very similar to toluene in its toxicological effects in that it is
primarily a skin irritant, and like other organic solvents it can produce
defatting dermatitis after prolonged exposure. Xylene acts as a narcotic if
inhaled in high concentrations.
Over 95% of xylene metabolism involves a pathway of oxidation to methylbenzyl
alcohol and subsequent reduction, via alcohol dehydrogenase by aldehyde
dehydrogenase, to methyl benzaldehyde and methyl benzoic (or toluic) acid
The major risk from xylene high level exposures is progressive inhibition of
nervous system function, culminating in coma, respiratory depression and
ultimately death from brain damage due to lack of oxygen.