An updated evaluation of the carcinogenic potential of 1,4-dioxane.

This paper presents a critical review of the information pertaining to the potential carcinogenicity of 1,4-dioxane. The primary target organs for cancer via the oral route are the liver and the nasal cavity, however, the relevance of nasal cavity tumors to human exposures has been questioned. Liver tumors were accompanied by degenerative changes and appear only to occur at high doses where clearance mechanisms are saturated and liver toxicity is significant. Genetic toxicity data suggests that 1,4-dioxane is a very weak genotoxin. An increase in hepatocyte cell proliferation was reported and 1,4-dioxane was shown to act as a tumor promoter in rat liver and mouse skin carcinogenicity assays. Two reports are available from the literature regarding physiologically based pharmacokinetic (PBPK) modeling approaches to assess the risk of liver cancer for 1,4-dioxane. A comparison of cancer risk estimates from linear and nonlinear models in the presence or absence of PBPK modeling suggests that USEPAs current cancer slope factor significantly overestimates the potential cancer risk from 1,4-dioxane. This critical review of the scientific literature indicates that a formal reevaluation of the carcinogenic potency of 1,4-dioxane is warranted.