[Relationship between half-lives of blood dioxins and possible metabolic mechanism].

Blood levels of dioxins in Yusho patients have been measured for 10 years. The purposes of this study were to determine the half-lives of dioxins on the basis of the data obtained from Yusho patients and to compare the half-lives of the compounds. Linear regression analysis was performed using the binary logarithmic value of each dioxin level as the dependent variable and the year of measurement as the independent variable. The linear coefficient obtained from this linear regression analysis was the reciprocal number of the half-life. The relationship between the blood dioxin levels estimated in 2004 and the reciprocal number of half-life was evaluated. Of the studied dioxins, the concentrations of some compounds were strongly correlated with that of 2,3,4,7,8-PeCDF. For 2 such compounds, the correlation coefficient of the reciprocal numbers of half-life were greater than the correlation coefficient of the logarithmic values of the estimated concentrations. Of these 2 compounds, the concentration of 3,3,4,4,5,5-HxCB was at least 50 times less than that of the 2,3,4,7, 8-PeCDF in rice oil: however, their current concentrations are equivalent. Patients with high levels of 2,3,4,7,8-PeCDF also showed high levels of 3,3,4,4,5,5-HxCB. Yusho patients may have a disease-specific mechanism to supply 3,3,4,4,5,5-HxCB.