Abstract

Toluene-xylene mixtures are used in industrial processes in several sectors. Workers are therefore exposed, either simultaneously or successively, to both solvents.

This study examined the effects of toluene and xylene exposure on human lymphocytes exposed in vitro and in vivo. Exposure of human subjects in the in vivo studies was rigorously maintained at levels below current exposure limits. Cell damage, mitotic index, and sister chromatid exchange all commonly used indicators of genotoxicity and mutagenicity were the biological end-points examined.

In the in vitro studies, cell damage was proportional to solvent concentration. The in vivo exposures produced a very weak response, in the form of a transient reduction in lymphocyte survival. The effects produced by toluene and xylene were neither additive nor synergistic.

The study demonstrated that exposure to toluene and xylene, either singly or in combination, at concentrations below current exposure limits does not constitute an occupational health hazard. The project also identified the most appropriate tests for these substances, and demonstrated the benefits of performing an exploratory study prior to undertaking costly experimental studies of workers.