[The changes of PCBs and PCDFs as well as symptoms in Yusho patients for 30 years]

Two mass-food poisonings called Yusho and Yucheng occurred in Western Japan and Taiwan in 1968 and 1979, respectively. Blood samples from 5 Yusho patients and 3 Yucheng patients were collected several times from 1982 to 1998 and from 1980 to 1995, respectively, and analyzed for PCB and PCDF congeners. Fat base concentrations of 2,3,4,7,8-penta-CDF in the Yusho patients, which were responsible for about 70% of the dioxin toxicity, are estimated to be decreased from 60 ppb in 1969 to 0.8 ppb in 1997 with the median half-life of 2.9 years in the first 15 years after the onset and 7.7 years in the next stage of 15 years. Fat base concentrations of total PCBs in the blood of Yusho patients are estimated to be decreased from 75 ppm just after the onset to 2.3 ppm after passage of 30 years. Typical Yusho symptoms of acneiform eruption, dermal pigmentation and increased eye discharge were very gradually recovered with lapse of ten years. However, enzyme and/or hormone mediated sign of high serum triglyceride, high serum thyroxin, immunoglobulin disorder and others are persistently maintained for 30 years.