Twenty-year changes of penta-chlorodibenzofuran (PeCDF) level and symptoms in Yusho patients, using association analysis

Using association analysis of the data mining technique, we extracted and compared combinations with a strong relationship between recent symptoms (2001-2004) and recent blood PeCDF levels, and between past symptoms (1986-1989) and recent PeCDF levels, in physical, blood, dermatological, dental and ophthalmological examinations.Patients with a higher PeCDF level were more likely to present with symptoms included in the diagnostic criteria, such as pigmentation. In addition, we obtained evidence that recent PeCDF levels had a stronger relationship with recent than past symptoms.Recent PeCDF levels should not be compared directly with past symptoms. However, as the excretion rate of PeCDF has been constant, it is probable that PeCDF levels were higher in the past if recent PeCDF levels were also high. The study confirmed a relationship between past PeCDF levels and past clinical symptoms. For symptoms included in the diagnostic criteria, there was a stronger relationship between PeCDF levels and past symptoms than recent symptoms. Alleviation of symptoms in each patient or aging weakened the relationship between PeCDF levels and symptoms.Kanemi Yusho is a form of food poisoning that was caused by rice bran oil in 1968 in Western Japan, especially in Northern Kyushu [1]. Initially, polychlorinated biphenyls (PCBs), which are used as a heat medium in the process of rice bran oil manufacture, were considered as the causative agents. However, subsequent research threw suspicion on 2,3,4,7,8-penta-chlorodibenzofurans (PeCDFs), which are dioxins that result from heat-denatured PCB, as causative agents. Today, PCBs and their derivatives are considered to be the main causative agents of Kanemi Yusho [1-5].With recent advances in measurement techniques for dioxins such as PeCDF, measurement of blood PeCDF levels has become possible using the same amount of blood as that used in the annual examinations. Since the Yusho examinations in 2001, PeCDF measurement has started for pat