Mycotoxins are naturally occurring contaminants produced by fungi that are ubiquitous, and man has always been exposed to these compounds in his diet. Fungi, like all heterotrophic organisms, need water and certain essential nutrients in order to live. Food crops represent a good source of nutrients for the moulds. As the moulds grow on these food commodities, they produce secondary metabolites including mycotoxins. Broadly defined, microorganisms can be considered to fall into one of three groups with respect to their requirement for water. In terms of 'water activity' (A_w) requirements, the thresholds for growth can be taken to lie around the points 0.95, 0.78 and 0.68 for hydrophyllic, mesophyllic and xerophyllic organisms, respectively. Certain fungi have ecological associations with certain crop plants and also certain production, processing or storage conditions favour specific fungi hence certain crops have a tendency to contain particular mycotoxins [xref] and not others.

Fungal toxins have been known to cause acute illness due to fungal toxins since at least the early medieval period when Saint Anthony's fire, now thought to have been caused by ergot alkaloids, was described. The first recognition of their importance in public health can be traced to the post-war period in Japan and Russia. Suspect rice supplies, despite severe scarcity of rice in Japan, were impounded and intense research into mycotoxins of rice was initiated. In the U.S.S.R., the deaths of large numbers of peasants led to the discovery of the trichothecenes. Mycotoxins became a public health priority in the west later when in the 1960's widespread deaths of turkey poults in the U.K., led to the discovery of aflatoxin and later to it's potent carcinogenic properties. Although cases of acute human mycotoxicosis continue to be reported, it is chronic exposure to mycotoxins, particularly for children, that is of much more widespread public health concern. Many countries have legislated maximum levels of certain mycotoxins in selected foods to ensure an acceptable level of protection for their citizens against the harmful effects of chronic exposure to these contaminants. FAO [www] published a compendium of worldwide regulations on mycotoxins in 1995.

Mycotoxins are naturally occurring contaminants produced by fungi that are ubiquitous, and man has always been exposed to these compounds in his diet. It is not possible to eliminate them completely from the food supply but by promoting good hygiene practices throughout the food chain, with emphasis on those points of the chain where there is greatest risk of this food hazard developing, the level of mycotoxins in foods can be reduced to tolerable levels. Several international codes of practice for the prevention/reduction of mycotoxin contamination in foods have been established in recent years. FAO has also been widely involved in the provision of direct technical assistance to member countries to strengthen mycotoxin prevention programmes.