Aflatoxin exposure, health impacts, risk assessment and database

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Aflatoxin exposure, health impacts, risk
assessment and database

• Aflatoxin Stakeholders Workshop
• 3-4 December , 2012
• Dar es Salaam , Tanzania
• Candida Philip Shirima

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Aflatoxins

• They are toxic and fungal metabolites
• Produced (A. flavus, A. parasiticus and rare
  A. nomius)
• Types aflatoxins B1 (AFB1) and B2 (AFB2), (AFG1)
  and G2 (AFG2).
• Aflatoxin B1 occurs most frequently and is most
  toxic and carcinogenic

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Human exposure to aflatoxins

• Dietary exposure The main source of human
  exposure to aflatoxins
• Exposure is through consumption of aflatoxins
  contaminated food.
• Contamination of maize and groundnuts is of
  particular concern- dietary staples including
  children complementary foods.
• The presence of aflatoxins metabolites in breast
  milk (AFM1) provides main source of aflatoxins
  exposure for lactating newborn infants and breast
  feeding young children
• Exposure from animal food products poultry

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Toxicokinetics of aflatoxin
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Aflatoxins exposure assessment

• Quantitative evaluation of the likely intake of
  aflatoxin via food.
• The extent of exposure to aflatoxins depends on
  the level of the toxin in different foods and on
  the level of consumption of those foods

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Ways of assessing exposure to aflatoxins-1

• Food measurement
• 1.Use levels of aflatoxin contamination in food
  and quantities of food consumption Probably daily
  intake (PDI)

Aflatoxin Contamination in food (ng/gm)
Food consumption (gm/day)
Aflatoxins exposure (ng/kg-bw/day)
Body weight (Kg)
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Ways of assessing exposure to aflatoxins-2

• Use of biomarkers of aflatoxin exposure
• Biomarkers are a measure of a cellular,
  biochemical or molecular change in biological
  media (human tissues, cells or fluids), which is
  informative with respect to assessing an exposure
• Use of biomarkers requires understanding of the
  mechanisms of aflatoxin actions

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Ways of assessing human exposure to aflatoxins-3

• Use of biomarkers of aflatoxin exposure
• Biomarkers of aflatoxin exposure include-
• Urinary aflatoxin metabolites, such as
  AFB1-N7-guanine and AFM1
• AF-albumin in blood serum, DNA adducts
• AFM1 in breast milk
• These metabolites are well validated as
  biomarkers of aflatoxin exposure.

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Aflatoxin research work by TFDA

• Completed study
• Iringa, Kilimanjaro, Tabora and Mtwara
• Aflatoxin occurance 18 in maize
• Contamination level range 1 to 158 µg/kg
• Ongoing studies
• Iringa, Kilimanjaro and Tabora (TFDA Leeds
  University)
• -Use of biomarkers in the evaluation of dietary
  exposure to aflatoxins and fumonisins among
  young children.
• -Association of children growth and exposure to
  the mycotoxins
• Hanang, Kilosa and Rungwe (TFDA and Ghent
  University)
• Strategies for reducing mycotoxins contamination
  and exposure-
• -Application of GPHP and dietary approaches
  /diversification

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Aflatoxins and health effects

• Aflatoxins are toxic in humans and animals
• Carcigonen AFB1 has been classified as a group 1
  human carcinogen by the IARC (1993).
• Associated with aflatoxicosis acute poisoning
  which results in direct liver damage and
  subsequent illness or death (Kenya in 2004)
• The liver Target organ for both acute and
  chronic aflatoxin toxicity
• High aflatoxin exposure is associated with
  impairment of child growth, particularly
  stunting the underlying mechanisms are unclear

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Aflatoxins and health effects

• Immune suppression effects
• Hepatopmegaly (liver enlargement) (in Kenyan
  school children)
• Nutritional interference effects
• -Aflatoxins bind covalently to DNA resulting in
  decreased protein synthesis
• -Selenium concentrations were found to be
  significantly and inversely correlated to
  AF-albumin adducts concentrations

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Why affects child growth?

• Hypothesis
• Intestine permeability and absorption impaired
• liver toxicity inhibit IGFs production which
  affect the growth axis
• Immune function suppression may enhance
  infectious disease e.g. diarrhoea
• Epigenetic changes occurred at early life
  exposure may have effect

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Aflatoxin risk analysis

• Develops an estimate of the risks
• Identifies appropriate measures
• Implement appropriate measures
• Communicates with stakeholders about the risks
  and measures applied

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Aflatoxin database

• Need for a centralised aflatoxin database
• -Food consumption data (AF susceptible foods)
• -Aflatoxin contamination data (to be coordinated)
• -Exposure assessment (e.g conventional
  biomarkers)
• -Aflatoxin risk analysis
• -Findings from aflatoxin studies
• Useful source of information for status of
  aflatoxin contamination, exposure and health
  effects in Tanzania
• Combine and share findings from various
  independent studies
• Good/accessible source of information for
  formulating sound strategies for AF control

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