Kolkata, Aflatoxins are poisonous substances produced by certain kinds of fungi (moulds) that are found naturally all over the world; they can...
Kolkata, Aflatoxins are poisonous substances produced by certain kinds of fungi (moulds) that are found naturally all over the world; they can contaminate food crops and pose a serious health threat to humans and livestock. Aflatoxins also pose a significant economic burden, causing an estimated 25 per cent or more of the world's food crops to be destroyed annually. Two closely related species of fungi are mainly responsible for producing the Aflatoxins of public health significance: Aspergillus flavus and A. parasiticus. Under favourable conditions typically found in tropical and subtropical regions, including high temperatures and high humidity, these moulds, normally found on dead and decaying vegetation, can invade food crops. Drought stress, insect damage and poor storage can also contribute to higher occurrence of the moulds including in more temperate regions.
Several types of aflatoxin (14 or more) occur in nature, but four – aflatoxins B1, B2, G1 and G2 are particularly dangerous to humans and animals as they have been found in all major food crops; but most human exposure comes from contaminated nuts, grains and their derived products. Additionally, aflatoxin M1 (AFM1), a product of aflatoxin B1 (AFB1) metabolism, can be found in milk in areas of high aflatoxin exposure. Subsequently humans may be exposed to this aflatoxin through milk and milk products, including breast milk, especially in areas where the poorest quality grain is used for animal feed. Food crops can become contaminated both before and after harvesting. Pre-harvest contamination with aflatoxins is mainly limited to maize, cottonseed, peanuts and tree nuts. Post-harvest contamination can be found in a variety of other crops such as coffee, rice and spices. Improper storage under conditions that favour mould growth (warm and humid storage environments) can typically lead to levels of contamination much higher than those found in the field.
National estimates of dietary exposure to aflatoxins indicate differences between developed and developing countries. In developed countries, mean aflatoxin dietary exposures are generally less than 1 ng/kg body weight (bw) per day (a nanogram is one billionth [1×10−9] of a gram), whereas estimates for some sub-Saharan African countries exceed 100 ng/kg bw per day, although these latter estimates are often based on very few data. Estimates of dietary exposure to AFM1 have rarely exceeded 1 ng/kg bw per day in any country (although up to 6.5 and 8.8 ng/kg bw per day for young children and breastfed infants have been reported).