Multi-year monitoring of Canadian grains and grain-based foods for trichothecenes and zearalenone.

Monitoring of Canadian grain crops and foods by the Health Protection Branch for deoxynivalenol (DON, vomitoxin) has been undertaken every year since 1980, when it was found in Ontario soft wheat for the first time (in the 1979 and 1980 crops). Contamination of this wheat crop has varied, with 22-100% incidences in all but 1 year and up to 0.75 micrograms/g for the annual means of positive samples. The Canadian guideline for DON is 2 micrograms/g in uncleaned soft wheat. Western Canadian hard wheat had < 10% incidence of DON in 7 crop years but 11-43% of samples analysed in 10 other years were positive. Wheat foods, including imports, have shown 9-90% incidences with annual mean levels of 0.07-0.58 micrograms/g in positive samples. Consistently high contamination of Ontario corn has been observed (13-100% annual incidences and annual means of positives 0.16-1.4 micrograms/g). Other trichothecenes, namely nivalenol and HT-2 toxin, have been found infrequently in Canadian grains. New analyses of Canadian and imported beers showed low ng/ml levels of DON. Grains destined for food use and corn foods have been analysed for zearalenone from 1986 to 1993. The most contaminated crop was Ontario; annual mean levels in positive samples ranged from 23 to 215 ng/g. Zearalenone has been detected infrequently in wheat, barley and soybeans (< 75 ng/g).