Human diploid lung fibroblast cells were exposed to various dose levels of ethylene oxide (EtO) to determine the relationship between dose, dose-rate or concentration-time effects and the formation of chromosome aberrations (CA), aneuploidy, and DNA single strand breaks (SSB) 1 day and 14 days following exposure. The chromosomal location of each CA was determined. Some of the CA experiments were also conducted with and without caffeine in the post-exposure culture medium to determine the ability of caffeine to enhance CA formation. Following 60 minute exposures with dose levels up to 10-15 mM, EtO increased the number of CA, aneuploidy, and SSB observed 20-22 hours following exposure. These effects occurred at dose levels which also resulted in some lethality and reduction in the mitotic index. Caffeine appeared to enhance the formation of CA, but 0.25 mM caffeine did not inhibit the repair of SSB at 1 day following EtO exposure. With an assay sensitivity limit of approximately 1 percent, no detectable increase in the percentage of aberrant cells was observed 14 days following exposure. An increase in the number of aneuploid cells was observed 14 days following exposure. A small increase in SSB 14 days following exposure to 10-15 mM EtO was not considered significant.

"Vicki Dellarco, project officer." "EPA/600/R-93/145." "December 15, 1992." Microfiche.