THE ROLE OF REGENERATIVE CELL-PROLIFERATION IN CHLOROFORM-INDUCED CANCER

Chloroform produces cancer by a nongenotoxic-cytotoxic mode of action, with no increased cancer risk expected at noncytotoxic doses. The def ault risk assessment for inhaled chloroform relies on liver tumor inci dence from a gavage study with female B6C3F(1) mice and estimates a vi rtually safe dose (VSD) at an airborne concentration of 0.000008 ppm o f chloroform. In contrast, a 1000-fold safety factor applied to the NO AEL for liver cytotoxicity from inhalation studies yields a VSD of 0.0 1 ppm. This estimate relies on inhalation data and is more consistent with the mode of action of chloroform.