Yusho disease

A similar relationship between PCDF isomers retained and apparently excreted has been observed for patients with the Yusho disease, an intoxication by a rice oil contaminated with PCBs and PCDFs. The contaminated rice oil and liver samples from two of the patients were analyzed and all the major PCDFs were identified. A comparison revealed that none of the isomers retained had two vicinal hydrogenated C-atoms in any of the two... 

Miyata H, Takayama K, Ogaki J, et al. 1989. Level of PCDDs, coplanar PCBs and PCDFs in patients with Yusho disease and in Yusho oil. Chemosphere 18 407-416. 

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. 

Table 2 Percentage of viaims showing symptoms of Yusho disease...

Aoki Y Polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzofurans as endocrine disrupters—what we have learned from Yusho disease. Environ Res 86 2-11, 2001... 

Table 6. Etiology of Yusho Disease - Role of PCDFs Toxicology of Yusho Oil Fractions...

Mass poisoning of more than 1000 people by contaminated rice oil (Yusho disease, Japan)... 

TCDD can produce respiratory irritation, but the findings from controlled epidemiologic studies do not support an association between 2,3,7,8-TCDD exposure and chronic respiratory disease. It should be noted, however, that chronic bronchitis and related effects were observed in many Yusho and Yu-Cheng patients, who were exposed to the structurally related CDFs (ATSDR 1994). 

However, a confounding factor in both Yusho and Yu-Cheng diseases... 

Because some of the symptoms of Yusho and Yu-Cheng diseases (see Table 2) were similar to those caused by PCDFs rather than PCBs, it has been concluded that these contaminants are the causative agents. Indeed the level of PCDFs in the blood of victims correlates with the symptoms whereas the blood level of PCBs does not. 

Mortality from Hodgkin s disease was increased in comparison to Taiwan national or local rates in the males (SMR=61.17, 95% Cl 1.55-340.72 or SMR=86.45, 95% Cl 2.19-481.52, respectively). There was no statistically significantly increased mortality from leukemia. The retrospective study Yusho victims summarized in Section 3.2.8.2.1 found no statistically significantly increased mortality from leukemia (Kuratsune et al. 1987). 

Chloracne tends to resolve slowly upon cessation of chemical exposure. Its duration correlates with the severity of the disease, which usually reflects the degree and extent of exposure. The severely exposed victims of Yusho in 1968 had characteristic chloracne lesions that continued to develop for as long as 14 years postexposure. 

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