[Analysis of residual nature of dioxins in blood of Yusho patients and controls in relation to the Yusho oil and food as respective exposure routes].

In this study, we examined the dioxin levels and congener distributions in blood samples of Yusho patients and normal control subjects, especially in relation to the respective exposure routes. Remarkable differences were observed between the blood of Yusho patients and general population in terms of both congener distributions and concentration levels. Cumulative dioxin intake for Yusho patients was estimated using the mean Yusho oil consumption and congener-specific dioxin contamination data for Yusho oil; for control subjects, it was estimated from food consumption and dioxin congener contamination data. Estimated total intake of dioxins was 2.44 microg-TEQ for control subjects and 357 microg-TEQ for Yusho patients, respectively. The total intake of some congeners such as 2,3,4,7,8-PeCDF and 1,2,3,4,7,8-HxCDF for Yusho patients was more than 100 times higher than those of control subjects. The congener distribution of PCB and PCDD in the blood of control subjects was similar to those of the food. In the case of Yusho patients, however, the congener distribution did not resemble those of either the food or the causal Kanemi rice oil, nor did not match that of control subjects' blood. Selective metabolizing of congeners was suggested to have occurred in the Yusho patients. In a 2001 fiscal year survey, the concentration ratio of TEQ between Yusho and normal subjects was 4.5. However, the level of 2,3,4,7,8-PeCDF, thought to be the congener that had the closest relation to various symptoms of the Yusho patients, was ten times or more in Yusho patients than in controls. It is suggested that further examinations should be conducted in the future to follow up this survey monitoring the blood levels of toxic congeners in Yusho patients.