Mice exposed in utero to low concentrations of benzene exhibit enduring changes in their colony forming hematopoietic cells.

Pregnant Swiss-Webster mice were exposed to either 0, 5, 10, or 20 ppm benzene from days 6 through 15 of gestation. Hematopoietic progenitor cell assays were performed on fetal, neonatal and adult progeny of the exposed dams. All concentrations of benzene employed induced marked changes in the numbers of the more differentiated erythroid colony forming cells, the CFU-E. Granulocytic colony forming cells (GM-CFU-C) were affected by the 2 higher exposure concentrations. When mice previously exposed in utero to 10 ppm benzene were re-exposed as adults, marked depressions in the numbers of CFU-E and GM-CFU-C were observed. Thus, in utero exposures to concentrations of benzene at the current occupational exposure limit induce alterations of the murine hematopoietic system which persist into adulthood.