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Skip to 0 minutes and 1 secondAflatoxin is metabolised in the body to produce aflatoxin albumin adducts in the blood, as well as other metabolites. Some of these can be used as biomarkers of exposure, such as the DNA adduct in urine or the albumin adduct in blood. The first study we will look at is one conducted in China, where maize was contaminated with aflatoxin. It compared the dietary intake of maize with the levels of the aflatoxin DNA adducts in urine. The study design used 42 adult participants from the Guangxi region in China. The participants included 30 males and 12 females, and maize consumption was 350 to 500 grammes per day. The study initially looked at one day's urine versus the previous day's diet intake.

Skip to 0 minutes and 52 secondsThen, it analysed seven days' dietary intake versus the last four days urine excretion. Urine metabolised alfatoxin N7 guanine, etc., were measured using monoclonal antibody affinity chromatography to clean up an HPLC analysis. This study shows that the biomarker reflected daily intake of aflatoxin and was therefore, a good biomarker for aflatoxin exposure. A subsequent study in China using the same biomarker for aflatoxin exposure confirmed the association between aflatoxin and liver cancer. This was a nested case control study, which means that the cases and the controls were selected from a large cohort study. In this case, it was a large cohort study with 70,000 person-year followup, 50 liver cancer cases and 267 controls, age and residence matched.

Skip to 1 minute and 50 secondsThe sample had been collected when the people had all been healthy. Over a period of several years, some people had developed liver cancer. Their urine samples, together with more controls, were tested for the levels of aflatoxin biomarkers in the urine. They were analysed for aflatoxin metabolites using previously mentioned method. The study shows that people who had been exposed to aflatoxin when the original samples were collected, were three times more likely to get liver cancer than people who had not been exposed to aflatoxin. People who had previously being infected with hepatitis B virus, but not exposed to aflatoxin, were seven times more likely to get liver cancer than people who were not infected with HBV.

Skip to 2 minutes and 39 secondsSo both aflatoxin and HBV could cause liver cancer. If someone had been infected with HBV and exposed to aflatoxin, they had a much higher risk of getting liver cancer. This showed that the two types of agents worked synergistically to increase risk of liver cancer. This study would not have been possible without the biomarker to assess aflatoxin exposure.

Aflatoxins and biomarkers

In terms of aflatoxin and human liver cancer, it was recognised that aflatoxin exposure was often common in regions where liver cancer incidence was high. It was also known that hepatitis B virus was prevalent in these regions.

With a clear linear association between incidence of liver cancer and aflatoxin intake in different countries, to better understand the role of diet-derived aflatoxin in human cancer development, a biomarker was needed to accurately determine aflatoxin exposure levels.

This video will describe the use of urinary aflatoxin DNA adducts as a biomarker to assess human aflatoxin exposure.

Deriving accurate exposure estimates is also challenging for several process-related contaminants, such as acrylamide which will be highlighted in a later step, and biomarker monitoring which is similarly used in determining human exposure levels to these contaminants as described in this paper by Reitjens (2018). A PDF is also provided in the downloads area.

  • Can you identify other relevant research or recent papers on aflatoxin or other contaminant exposure that have used biomarkers to determine human exposure levels?

Please share your thoughts and comments with other learners in the discussion area.

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This video is from the free online course:

Tackling Global Food Safety

Queen's University Belfast