Aflatoxin, hepatitis and worldwide liver cancer risks.

Aflatoxins are among the most potent mutagenic and carcinogenic substances known. Differential potency of aflatoxin among species can be partially attributed to differences in metabolism; however, current information on competing aspects of metabolic activation and detoxification of aflatoxin in various species does not identify an adequate animal model for humans. Risk of liver cancer is influenced by a number of factors, most notably carriage of hepatitis B virus as determined by the presence in serum of the hepatitis B surface antigen (HBsAg+ or HBsAg-). About 50 to 100% of liver cancer cases are estimated to be associated with persistent infection of hepatitis B (or C) virus. The potency of aflatoxin in HBsAg+ individuals is substantially higher (about a factor of 30) than the potency in HBsAg- individuals. Thus, reduction of the intake of aflatoxins in populations with a high prevalence of HBsAg+ individuals will have greater impact on reducing liver cancer rates than reductions in populations with a low prevalence of HbsAg+ individuals. The present analysis suggests that vaccination against hepatitis B (or protection against hepatits C), which reduces prevalence of carriers, would reduce the potency of the aflatoxins in vaccinated populations and reduce liver cancer risk.