Virtually all the plant pathogenic fungi are able to produce, in appropriate conditions, secondary metabolites that are toxic to invertebrate or vertebrate animals. To date, approximately 400 toxic secondary metabolites of fungal plant pathogens have been discovered. Many of these have been isolated from laboratory cultures and only a relatively limited number of them have been found to occur under natural conditions, where they play the roles of chemical weapons against competing microorganisms and grazing animals, of virulence factors, or of signaling molecules within ecological interactions. Among the naturally occurring fungal toxins only few are considered mycotoxins of significance for human and animal health because of their high toxicity, levels produced (especially in certain epidemiological conditions), or chances of exposure and intake. The most important mycotoxigenic fungal species belong to the genera Aspergillus, Penicillium and Fusarium, which can contaminate staple crops and widely consumed foods (Table 1), such as cereals (maize, wheat, barley, oats and rice), nuts, oilseeds, fruits, dried fruits, vegetables, cocoa and coffee beans, wine, beer, herbs, and spices and therefore pose a risk to a large number of people and animals (See "Relevant Website section"). To protect consumers from health risks, many countries have adopted regulations to limit exposure to the major mycotoxins. A study from 2003 by the United Nations’ Food and Agriculture Organization (FAO) on worldwide regulations for mycotoxins reported that at that time approximately 100 countries had established guidance and regulations on mycotoxin in food and feed (FAO, 2004). To date, the figures are possibly higher, but still there are countries, including a number of African countries, which do not have specific regulation for food safety (Matumba et al., 2015). Also, many countries have regulated the tolerable levels for at least aflatoxin B1 (AfB1)orthesumofaflatoxins B1,B2,G1 and G2 in human food, but relatively few countries have established strict limits for other mycotoxins such as fumonisin (FUM), ochratoxin A (OTA), and deoxynivalenol (DON). For, instance, in the USA, maximum tolerated levels have been set by the Food and Drug Administration (FDA) for aflatoxins in food and feed and for patulin, but only guidance levels are given for DON and FUM in food and feed (FDA, 2000).
Table1. Major mycotoxins and mycotoxigenic fungi
The various regulations set the limits for the content of mycotoxins in food and feed and, naturally, they have profound implications for health safety as well as for economic interests of producers and traders. However, the different perceptions of tolerable health risks of mycotoxins at global level, mainly associated to the level of development and susceptibility of crops to contamination in different countries, has led to lack of consensus about standards for regulated mycotoxins in food and feed (Tables 2 and 3). For example, of the 48 countries which in 2003 had established limits for total aflatoxins in food, standards ranged from 0 to 50 mg/Kg (ppb) (Dohlman, 2003). Most of the limits are set for human foods. Typically, higher regulatory levels are used for animal feed.
Table2. Standards for mycotoxins in food adopted in some countries and recommended by the Codex Alimentarius
Table2. Continued
Table3. standards for mycotoxins in feed adopted in some countries
Table3. Continued
One more complication may arise from some countries that under the “precautionary principle” may want to set standards on certain mycotoxins for which scientific evidence of a health risk is not yet well-established. In this respect, harmonization of regulations and guidelines for production and surveillance is a crucial issue, with the aim to find an acceptable balance between health benefits and economic and trade costs. For this reason, a joint scientific expert committee (Joint FAO/WHO Expert Committee on Food Additives, JECFA) of the FAO and the World Health Organization (WHO), has been instituted as the international body responsible for evaluating the health risk from mycotoxins. International standards and codes of practice to limit exposure to mycotoxins from certain foods have been established by the Codex Alimentarius Commission based on JECFA assessments (Codex Alimentarius, 2015). However Codex standards are advisory, not mandatory, and the national standards may divert significantly from the Codex recommendations.
