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Yusho disease, a polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF) mixed poisoning caused by contaminated rice oil, occurred in Japan in 1968. The evidence on reproductive outcome is limited. We therefore evaluated the regional impact of the exposure to the PCB and PCDF mixture on stillbirth rate and secondary sex ratio among the residents in two severely affected areas. We selected the regionally-affected towns of Tamanoura (n=4390 in 1970) and Naru (n=6569) in Nagasaki Prefecture, Japan, for study. We obtained data on stillbirths (spontaneous/artificial) and live-born births (total/male/female) from 1958 to 1994. For a decade and a half after the exposure, an increase in the rate of spontaneous stillbirths coincided with a decrease in the male sex ratio. Compared with the years 1958-1967, the ratios for spontaneous stillbirth rates were 2.16 (95% confidence interval: 1.58 to 2.97) for 1968-1977 and 1.80 (95% confidence interval: 1.25 to 2.60) for 1978-1987. The sex ratio (male proportion) was 0.483 (95% confidence interval: 0.457 to 0.508) in the first 10years after exposure. Exposure to a mixture of PCBs and PCDFs affected stillbirth and sex ratio for a decade and a half after the exposure., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In Japan in 1968, rice-oil contaminated by polychlorinated biphenyls and polychlorinated dibenzofurans caused severe food poisoning, termed "Yusho" (oil disease). Several previous studies attempted to evaluate the effects targeting officially-certified Yusho patients. However, these studies have several limitations such as the left-truncated nature of the registry or residual confounding arising from the referent population selection. We thus conducted an area-based standardized mortality ratios (SMRs) study using vital statistics. A severely affected area (Tamanoura area) was adopted as the exposure group, with a reference population from Nagasaki prefecture in Kyushu, which included the Tamanoura. A large number of residents in Tamanoura were exposed to the rice-oil (28% of all the certified cases as of 2009). We estimated SMRs of non-cancer and cancer diseases for the years 1968-2002. Shortly after the exposure, SMRs of all causes, diabetes mellitus, cardiovascular disease, pneumonia/bronchitis, and bronchus/lung cancer were elevated. In particular, SMRs of heart disease were 1.97 [95% confidence intervals (CI): 1.09-3.56] in 1968, 2.05 (95% CI: 1.16-3.60) in 1969, and 1.89 (95% CI: 1.05-3.41) in 1975. However, we did not observe clear increase in SMRs more than 10 years after the exposure. This study provides further evidence in Yusho, especially on acute effects on non-cancer mortality., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Severe methylmercury poisoning occurred in Minamata and neighboring communities in Japan during the 1950s and 1960s, causing what is known as Minamata disease. Although an increase in stillbirths and a reduced male proportion at birth (i.e., reduced sex ratio) have been reported, no studies have evaluated the impact of exposure on an entire set of infant and birth outcomes. We therefore evaluated the temporal trends of these outcomes in the Minamata area from 1950 to 1974. We focused on the spontaneous/artificial stillbirth rate, crude fertility rate, male proportion at birth, male proportion among stillbirths, and infant mortality. We obtained the number of stillbirths, live births, and infant deaths in Minamata City and Kumamoto Prefecture (as a reference) from 1950 to 1974. After plotting annual figures for each outcome, we divided the study period into five intervals and compared them between Minamata City and Kumamoto Prefecture using the chi-squared test. We observed a slightly increased spontaneous stillbirth rate and decreased artificial stillbirth rate in Minamata City, followed by a reduced crude fertility rate. The crude fertility rates in Minamata City during the period 1955–1965 were significantly lower compared with those in Kumamoto Prefecture (p < 0.001). An increase in the male proportion among stillbirths was observed, corresponding to a reduction in the proportion of males at birth in the late 1950s. The impact on infant mortality was equivocal. These descriptive analyses demonstrate a severe regional impact of methylmercury exposure on a series of birth outcomes in the Minamata area. [ABSTRACT FROM AUTHOR]