Yusho poisoning

Menstrual irregularities (i.e., altered intervals, duration, and flow) were observed in women exposed during the Yusho poisoning incident (Kusuda 1971). Heating of the PCB-contaminated rice oil also resulted in the formation of other contaminants of concern (i.e., dibenzofurans and ter-, and... 

Anomalies in toxicological test results and in particular the Yusho poisoning outbreak in Japan, led to a more intensive search for impurities. As many of the parent hydrocarbon feedstocks are derived from oil or coal tar sources, they tend to be contaminated by other aromatics, especially each other so PCN may be found in PCB, and vice versa, but at levels well below 0.1%. 

Kuratsune M, Yoshimura T, Matsuzaka J, Yamasuchi A Yusho, a poisoning caused by rice oil contaminated with polychlorinated biphenyls. HSMHA Health Rep 36 1083-1091, 1971... 

Kuratsune, M., T. Yoshimura, J. Matsuzaka and A. Yamaguchi, "Epidemiologic Study (on) Yusho, A Poisoning caused by Ingestion of Rice Oil contaminated with a Commercial Brand of Polychlorinated Biphenyls," Environ. Health Perspect.. Exp. Issue No. 1, pp. 119-28 (Apr. 1972). 

Ikeda, M., 1996. Comparison of clinical picture between Yusho/Yucheng cases and occupational PCB poisoning cases. Chemosphere 32, 559-566. 

Ryan JJ, Levesque D, Panopio LG, etal. 1993a. Elimination of polychlorinated dibenzofiirans (PCDFs) and polychlorinated biphenyls (PCBs) from human blood in the Yusho and Yu-Cheng rice oil poisonings. Arch Environ Contain Toxicol 24 504-512. 

The carcinogenic effects of PCDDs and PCDFs have been extensively investigated in several highly exposed groups, including industrial workers, herbicide applicators, individuals poisoned in the Yusho and Yu-Cheng incidents in Japan... 

The adverse human impacts of PCBs have been investigated in occupationally exposed workers as well as individuals poisoned with PCB-contaminated rice oil in Japan and Taiwan (Yusho and Yu-Cheng poisonings).91,107-109 In addition, recent studies have shown a correlation with in utero exposure to PCBs and subtle neurodevelopmental and neurobehavioural deficits in children.110 These effects were observed in children with relatively low-level environmental exposure to PCBs and thus have raised concerns regarding the potential adverse effects of low level in utero exposure to organochlorine compounds during critical periods of foetal development. 

The potential toxicity of PCBs to humans first came into the public arena in 1968, when over 1,500 people around Fukuoka in south-west Japan were poisoned by eating food cooked in rice oil contaminated with PCBs. This was not a single (acute) poisoning incident as the victims used the contaminated rice oil for cooking for some three months. The oil had become contaminated with PCBs as a result of a leak in the machinery in the plant producing the rice oil. People started to suffer from various diseases, and the illness became known as Yusho disease (meaning rice oil disease). Most prominent was chloracne, a severe effect on the skin which is also caused by dioxins. Babies born to women who were exposed also showed symptoms of the disease. Eventually some 2,000 cases of Yusho disease were recorded. 

These PCDFs were stiU detectable in victims of the poisoning more than eleven years after the exposure, and they seemed to be retained more than PCBs. They have been detected in the livers of victims of Yusho disease some years after the exposure occurred. Furthermore, the isomers and congeners (see box) retained in the livers were the most toxic, it would seem because these are more resistant to metabolism and so are more persistent. 

PCDFs are very similar to dioxins and, like them, are very toxic, especially 2,4,7,8-tetrachlorodibenzofuran, although this is not quite as toxic as TCDD. They have been found to be contaminants of PCBs and in the Yusho and Yu-Cheng poisoning incidents were more abundant in the PCBs than was usual. As with dioxins and PCBs, there are many different isomers and congeners. 

Evaluation of Human Studies. Limited information on immunological effects of PCBs in humans is available from studies of people exposed in the workplace, by consumption of contaminated fish and other marine foods, by consumption of contaminated rice oil in the Yusho and Yu-Cheng poisoning incidents, and via general enviromnental exposures. A comparison of PCB levels in blood and breast milk in some of these studies is included in Appendix A. 

Kashimoto T, Miyata H. 1986. Differences between Yusho and other kinds of poisoning involving only PCBs. In Waid JS, ed. PCBs and the environment, Vol. III. Boca Raton CRC Press, 2-26. 

MasudaY. 1994. The Yusho rice oil poisoning incident. In Schecter A., ed. Dioxins and health. 

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