A recent study published in Environmental Health Perspectives looked at the relationship between aflatoxin, produced by certain mold growing on food, and liver cancer. The results are a bit of an eye opener – they suggest that, at the upper end of their estimate, aflatoxin may cause almost 30% of all cases of liver cancer worldwide.
First, a bit of background. Aflatoxins are a group of toxic compounds produced by fungi from the genus Aspergillus. One of these, Aflatoxin B1, is a very potent liver carcinogen, classified as a confirmed human carcinogen by the International Agency for Research on Cancer. The risk of developing cancer is much higher in people infected with hepatitis B; it also appears to act synergistically with hepatitis C.
The type of Aspergillus that produces Aflatoxin B1 is found mainly on corn, peanuts, cottonseed and tree nuts, although it can be found on other crops after improper storage. It grows primarily in warmer climates, and generally isn’t found in Canadian-grown crops; however, with global transport of crops it can be found worldwide.
The authors of the Environmental Health Perspectives study, Yan Liu and Felicia Wu, looked at how much aflatoxin people are exposed to worldwide, based on concentrations measured in food and food consumption data. They also looked at the relationship between exposure to aflatoxins and the development of liver cancer, for people with and without chronic hepatitis B, and the prevalence of hepatitis B in different parts of the world. From these data, they estimated the annual incidence of hepatocellular carcinoma (liver cancer) in different parts of the world for people with and without hepatitis B. There are obviously some limitations in the underlying data, resulting in uncertainty in the estimates, but overall they found that aflatoxin likely has a causative role in at least 4.6% of all cases of hepatocellular carcinoma, and as high as 28.2%.
Even given the uncertainty in the estimate, these numbers indicate that aflatoxin is a fairly major public health issue. The majority of aflatoxin-caused cancers occur in developing countries, due to the increased occurrence of Aspergillus in tropical climates, poor food handling and storage, and generally higher incidence of chronic hepatitis B, though there is still exposure to aflatoxin in Canada and other developed countries.
So what can be done to reduce the effects of aflatoxin? Obvious measures that come to mind are reducing Aspergillus growth on crops, including proper crop storage, and where necessary use of (approved and safe) fungicides. The effects of aflatoxin could also be substantially reduced by increasing hepatitis B vaccinations in countries with either high rates of hepatitis B or high aflatoxin exposures.
Liu, Y., & Wu, F. (2010). Global Burden of Aflatoxin-Induced Hepatocellular Carcinoma: A Risk Assessment Environmental Health Perspectives, 118 (6), 818-824 DOI: 10.1289/ehp.0901388