ArticlesReduction in exposure to carcinogenic aflatoxins by postharvest intervention measures in west Africa: a community-based intervention study
Introduction
Staple foods in west Africa and other parts of the developing world are frequently contaminated with aflatoxins, metabolites of aspergillus species.1 Aflatoxins have a carcinogenic action on the liver and act synergistically with chronic hepatitis B virus.1 A joint Food and Agriculture Organisation of the United Nations/WHO committee thus concluded that reduced intake of aflatoxins in places where infection with hepatitis B virus is endemic would have a substantial effect on the incidence of hepatocellular carcinoma,2 which accounts for about a fifth of all cancers in men in west Africa.3 Furthermore, aflatoxins can cause growth inhibition and immune suppression in animals.4 Consistent with these observations, aflatoxin exposure in west Africa at the time of weaning has been associated with impaired child growth5, 6, 7 and with a decreased immune response.8 These health effects further emphasise the potential benefit to public health of reducing aflatoxin exposure in developing countries.
Aflatoxin contamination of foods is especially severe after long-term crop storage because excessive heat, humidity, and insect and rodent damage result in proliferation and spread of fungal spores. The main crops affected include maize (corn) and groundnuts (peanuts), which together are the main dietary staples in many parts of sub-Saharan Africa. The reliance on subsistence farming, the limited food diversity, and toxin contamination result in high aflatoxin exposures throughout life.9 By use of a blood-based biomarker, aflatoxin–albumin adducts, data for several west African countries show that more than 98% of children and adults have detectable amounts in their blood.9, 10 Exposures are orders of magnitude higher than those allowed by regulation in Europe, the USA, and other parts of the developed world.
Several approaches can prevent aflatoxin exposure in developing countries.11 Because much food contamination occurs during postharvest storage, methods to remove nuts or kernels damaged by fungus before storage and to restrict humidity during storage could reduce fungal growth and toxin production. However, the effect of this strategy on exposure in subsistence-farming communities in Africa has not been assessed.
Our aim was to assess the use of improved methods of groundnut storage for subsistence farmers in a rural area of Guinea. Aflatoxin and infection with hepatitis B virus are endemic in this region, and groundnuts are the main source of aflatoxin exposure.12, 13, 14 We introduced a package of postharvest intervention measures to farmers in ten villages at the time of groundnut harvest and made comparisons with farmers in ten neighbouring villages that used usual storage practices.
Section snippets
Participants
The study was undertaken in 20 villages in the Kindia prefecture of lower Guinea, which were close to each other (within about 60 km of Kindia) to ensure that climate—as well as practices of groundnut cultivation, harvesting, and storage—were much the same in all villages. The ten intervention villages were to the north of Kindia and ten control villages were to the southeast to keep to a minimum the risk of prevention strategies being used in control villages.
In every village we recruited, by
Results
150 pairs of men and women were recruited from ten villages for both the intervention and control groups. Participants in the intervention group were younger than those in the control group (table 1). Three main ethnic groups (Soussou, Peulh, and Kissi) were represented, and intervention villages had an over-representation of Soussou compared with the control group. Neither age nor ethnic group correlated with concentrations of aflatoxin–albumin adducts. Data were obtained for 535 (89%) of 600
Discussion
This community-based intervention has shown a striking reduction in aflatoxin exposure by use of simple, low-technology postharvest practices in a rural subsistence-farming community. Exposure was more than halved 5 months after harvest in individuals from the intervention villages. Moreover, only 2% of individuals in the control villages had undetectable concentrations of aflatoxin–albumin adducts compared with about 20% in the intervention villages. In west Africa more than 98% of people test
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