CYTOGENETIC EFFECTS OF LOW-LEVEL EXPOSURE TO TOLUENE, XYLENE, AND THEIR MIXTURE ON HUMAN BLOOD-LYMPHOCYTES

The present study was undertaken to investigate, both in vitro and in vivo, the genotoxic potential of short-term low-level exposure to tolu ene, xylene, and their mixture, for which information is limited at th e present time. Five adult healthy white men were exposed for 7 consec utive hours per day over 3 consecutive days to 50 ppm toluene and 40 p pm xylene either alone or in combination in a controlled exposure cham ber. Such an exposure was repeated three times at intervals of 2 weeks . Blood samples were taken before and after the termination of such ex posure. Three different cytogenetic endpoints were evaluated using per ipheral blood lymphocytes: number of sister chromatid exchanges (SCEs) , cell cycle delay, and cell mortality. No significant effects on SCEs , cell cycle delay, and cell mortality were observed following such ex posure to toluene or xylene or their mixture. Similarly, exposure of h uman blood lymphocytes in vitro to either toluene (0-2.5 mM) or xylene (0-2 mM) or their mixture for 72 h did not result in any significant cytogenetic effects at lower concentrations, while at higher concentra tions, only cell mortality was found to be significantly affected. Thu s our present study indicates that simultaneous exposure to low levels (within the admissible limits) of toluene, xylene, or their mixture f or a short period does not pose any potential mutagenic threat to huma ns.