The carcinogenicity of dichloroacetic acid in the male B6C3F sub(1) mouse

Groups of male B6C3F sub(1) mice (N = 50) were provided drinking water containing 2 g/liter sodium chloride (control) and 0.05, 0.5, and 5 g/liter dichloroacetic acid (DCA). Treatment of 30 animals in each group was carried out to 60 or 75 weeks. In a separate experiment, mice exposed to 3.5 g/liter DCA and the corresponding acetic acid control group were killed at 60 weeks. Groups of 5 mice were killed at 4, 15, 30, and 45 weeks. There was a significant positive dose-related trend in the age-adjusted prevalence of liver tumors. These data confirm the hepatocarcinogenicity of DCA administered in the drinking water to male B6C3F sub(1) mice for 60 weeks. The results together with those in an earlier report from this laboratory suggest, for the conditions under which these assays were conducted, a threshold concentration of at least 0.5 g/liter followed by a steep rise to a maximum tumor incidence at 2 g/liter DCA.