Levels and pattern of contamination with trichothecenes in cereal grains and their risk assessment

often in oat, rice, rye, sorghum, and triticale. The occurrence of trichothecenes is mainly associated with Fusarium species which are important plant pathogenic fungi, causing several crop diseases such as head blight in wheat and ear rot in maize. After consumption of Fusarium-infected grains, the emetic effect occurs in humans as one of earliest symptoms of trichothecenes. Deoxynivalenol (DON) and nivalenol (NIV) are major trichothecenes, and had caused animal and human intoxication in Japan. Occurrence of DON in wheat and barley is associated primarily with Fusarium graminearum (teleomorph; Gibberella zeae) in Japan, and also with F. culmorum in foreign countries. F. graminearum is divided into two populations; DON-producing F. graminearum and NIV-producing F. graminearum. Interestingly, their distribution has geographical difference in local fields of Japan, and their niches are closely related to the proportion of DON/NIV in wheat and barley grains harvested. In Hokkaido and Tohoku districts, DON-producing F. graminearum exists predominantly whereas, NIV and DON-producing F. graminearum are widely distributed south of the Tohoku district. Hence, co-occurrence of DON and NIV in wheat and barley is commonly found as reported earlier. In Hokkaido, the levels and frequency of DON is prevailing to those of NIV. However, the levels and frequency of NIV has gradually increased south of the Tohoku district. The proportion of DON/NIV in wheat and barley ranges from 30 to 80 %. As other NIV-producing Fusarium species, F. poae and F. crookwellense distribute widely in the crop fields of Hokkaido, and they are responsible for NIV contamination in wheat and barley cultivated in Hokkaido. On the other hand, the surveys in Korea suggest that NIV occurs mainly in cereals due to prevailing NIV-producing F. graminearum. Further, surveys have indicated that co-contamination of DON and NIV was common in cereal grains harvested from 21 countries in the world although, the level and frequency of DON/NIV was different. In 2001, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) established 1 μg/kg of body weight per day as a provisional maximum tolerable daily intake (PMTDI) for DON based on the results of a 2-years feeding study in mice. In Japan, the Ministry of Health, Labor and Welfare recommended 1.1 mg/kg of DON levels as provisional standard for local governments in unpolished Vol. 53 (2), 2003 119 Mycotoxins Vol. 53 (2), 2003