[Trend of PCB/PCDF concentrations in the blood of Yusho patients for 38 years after the incidence].

Concentrations of 2,3',4,4',5-pentaCB (PCB118), 2,2',4,4',5,5'-hexaCB (PCB153), 2,3,3',4, 4',5-hexaCB (PCB156) and total PCB congeners (PCBs) in the blood of Yusho patients, surveyed by the annual medical examination in Fukuoka Prefecture, have been gradually decreased from 1974 (7 ppb) to 2006 (3 ppb). The patients are classified into 3 types of Yusho, namely, Yusho A: having typical Yusho gas chromatogram (GC) pattern, Yusho B: between Yusho A and Yusho C, and Yusho C: having GC pattern similar to those of Controls. The concentrations of PCB153, PCB156 and PCBs in the blood of Yusho A were higher than those of Yusho B and Yusho C in order. However, the concentrations of PCB118 in the blood of Yusho A were lower than those of Yusho B and Yusho C in order. Simple correlation coefficients between the concentrations of PCB118, PCB153, PCB156 and PCBs in the blood of Yusho patients and their ages at the blood sampling were examined from 1974 to 2006. The significant correlations were rather rare among them from 1974 to 1991, increasing number to 2000, and finally almost all to 2006, as observed in the blood of Fukuoka Controls in 1999 in which all the correlations are significant. However, the correlation coefficients between the concentrations of PCB118 and PCB156 in the blood of Yusho patients have been insignificant throughout from 1974 to 2006 with a few exceptions. By the use of the data of 3 Taiwan Yucheng patients and 5 Fukuoka Yusho patients, chronological concentrations of PCB118, PCB153, PCB156, 2,3,4,7,8-pentaCDF (23478F) and 1,2,3,4,7,8-hexaCDF (123478F) in the blood of Yusho patients were figured out from the outbreak of the poisoning to the present for 38 years. Very high concentrations of PCBs (20-90 ppb) and PCDFs (100-500 ppt) just after the onset were gradually decreased to 0.04-1.3 ppb of PCBs and 0.3-5 ppt of PCDFs in 2005 with the biological half-lives of 3.84, 6.31, 7.24, 4.98 and 4. 30 years, respectively. The particular declining mode of the PCB congeners during 38 years and the correlation coefficients between the concentrations of PCB118, PCB153, PCB156, 23478F and 123478F in the blood of Yusho patients indicated that PCB118 concentrations have been decreased by the coexisting PCB156, 23478F and others which have very strong enzyme inducing activities and the PCB118 has been metabolized by the enzyme inducers to hydroxyl-PCBs which firmly bind to transthyretin (thyroxin transport protein) in the blood and disturb the hormonal effects.