Risk Assessment of Fumonisins Produced by Fusarium moniliforme in Corn

Abstract

Four important toxigenic species of fungi are associated with corn (Zea mays) intended for human and animal consumption in South Africa, ie Aspergillus flavus, Diplodia maydis, Fusarium graminearum, and Fusarium moniliforme. Com infected by these fungi causes outbreaks of the following mycotoxicoses in animals: aflatoxicosis, diplodiosis, hyperestrogenism and leukoencephalomalacia. The five most important mycotoxins known to occur naturally in corn in South Africa are aflatoxins, deoxynivalenol, nivalenol, zearalenone and fumonisins. The following mycotoxins in foods have been implicated in human diseases in South Africa: aflatoxins in acute toxic hepatitis, kwashiorkor and liver cancer and fumonisins in oesophageal cancer. Tolerance levels of mycotoxins in grain are essential to protect human health and to assess grain quality from the viewpoint of mycotoxin contamination. Tolerance levels are established by means of risk assessment studies. Risk assessment of mycotoxins in grains has two major components, ie exposure assessment and hazard assessment. Exposure is calculated from naturally occurring levels of a mycotoxin in foodstuffs and food intake and expressed as the Probable Daily Intake (PDI). Hazard is calculated from toxicological studies in experimental animals by dividing the No Observed Effect Level (NOEL) by a Safety Factor (ranging from 100 to 5000) and expressed as the Tolerable Daily Intake (TDI). Several estimates of PDI and TDI values of fumonisins in corn are compared and a tolerance level of 100 to 200 μg/kg for fumonisins in corn intended for human consumption is suggested. However, more work remains to be done to establish scientifically sound and economically reasonable tolerance levels for fumonisins in corn.