Yusho: 43 years later

Abstract

The aim of the present study is to describe recent issues with Yusho disease in Japan, describe the state of dioxin accumulation and the intake of dioxin via food in Japan, and introduce the Japan Environment and Children's Study. Yusho disease manifested in western Japan in 1968. The causes of Yusho are believed to be dioxin-related compounds, mainly polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs), via the ingestion of rice oil produced in February 1968. As of March 31, 2011, there were 1961 registered Yusho cases, but of these 539 are deceased. A retrospective cohort study on registered Yusho cases reported that the standardized mortality ratios (SMRs) for the major causes of death were not significantly elevated, with the exception of all-cancer (SMR=1.26; 95% confidence interval [CI]: 1.03-1.53) and lung cancer mortality (SMR=1.56; 95% CI: 1.03-2.27) in males. The results of the Yusho mortality study show that the SMR for liver cancer in males tends to decrease over time. In 2011, the Ministry of the Environment of Japan reported that the average concentration of dioxins in the blood (2002-2010) of the Japanese people was 19 pg-TEQ/g-fat, demonstrating a range of 0.10-130 pg-TEQ/g-fat, and that the average dioxin intake from food (2002-2010) was 0.82 pg-TEQ/kg-body weight/day, demonstrating a range of 0.031-6.2 pg-TEQ/kg-body weight/day according to 2006 WHO TEFs. The Japan Environment and Children's Study Project was launched in 2011 and is supported by the Ministry of the Environment of Japan. In this project, 100,000 mother and child pairs will be recruited over 3 years from designated study areas. Follow-up examinations will be carried out from pregnancy until the children are 13 years of age (a so-called birth-cohort study). This project will be implemented by the National Center at the National Institute for Environmental Studies and is supported by the Medical Support Center at the National Center for Child Health and Development. Field operations will be performed at 15 designated regional centers nationwide.