Although it is well known that a hot and humid climate promotes diffusion of aflatoxin-producing moulds, representing a greater hazard in tropical areas of the world, the contamination is commonly due to the combination of meteorological conditions, environmental factors and improper agricultural practices, like incorrect harvesting and storage of crops.
Aflatoxins are colorless to pale yellow crystals, exhibiting fluorescence under UV light. They are slightly soluble in water (10-20μg/ml) and freely soluble in moderately polar solvents such as chloroform, menthol and dimethyl sulfoxide.
Ten-odd isomers of aflatoxin have been discovered. However, most of those detected in feed contaminated with molds are B1, B2, G1 and G2. M1 is a substance that is detected in the milk of cows which have taken feed contaminated with B1.
As for physicochemical properties, aflatoxin is a highly fluorescent substance, and B1, B2, M1 and M2 emit blue fluorescence, while G1 and G2 emit green fluorescence.
Among these toxins, Aflatoxin B1 (AFB1) is considered the most recurrent and also the most harmful. Its carcinogenicity and immunosuppression capacity have been extensively reported in all kind of animals, including poultry, trout, cattle and rats with different incidence across species, gender and age.
Aflatoxins were first identified in 1961 in United Kingdom in animal feed responsible for the deaths of 100 000 turkeys.
Properties and characteristics of aflatoxins 
