DOES AFLATOXIN EXPOSURE IN THE UNITED-KINGDOM CONSTITUTE A CANCER RISK

Although the aflatoxins were discovered more than 30 years ago, there is still considerable controversy surrounding their human health effects. Most countries have introduced legislation to control the level of aflatoxins in food, but it is not known if these permitted levels still pose a significant cancer risk. Furthermore, it is unlikely that all the sources of human aflatoxin exposure have been discovered, nor if the liver is the only, or indeed, major target organ for aflatoxin-induced cancer in man. In our laboratory we have used both immunological and HPLC methods to examine human DNA from a variety of tissues and organs to identify and quantify aflatoxin DNA-adducts. We have already detected aflatoxin B1 (AFB1)-DNA adducts in formalin-fixed tissue from an accute poisoning incident in Southeast Asia. Here we have examined human colon and rectum DNA from normal and tumorous tissue obtained from cancer patients and colon, liver, pancreas, breast, and cervix DNA from autopsy specimens. AFB1-DNA adducts were detected in all tissue types examined and ranged from 0-60 adducts/10(6) nucleotides. Where sample size allowed, the adduct levels were confirmed by HPLC analysis. Tumor tissues tended to have higher adduct levels than normal tissue from the same individual, and levels generally increased with patient age. In samples analyzed by HPLC, the adducts present had the chromatographic properties of [8,9-dihydro-8-(N5-formyl)-2',5,6'-triamino-4'-oxo-(N5-pyramidyl)-9-hydroxy-aflatoxin B1, the ring-opened form of the AFB1-guanine adduct. The level of adducts observed in individuals from the UK were often in the same range as those seen in citizens of Third-World countries. AFB1-DNA adduct values in this range, i.e., 1/10(6), have been reported to result in the development of tumors in rats and trouts dosed with AFB1. This would indicate that aflatoxins may pose a carcinogenic risk to a variety of organs for the UK population and that there are either unknown sources of aflatoxin in our diet or that the present permitted level in food is too high.