Abstract
Mass poisonings, called yusho and yu-cheng, occurred in western Japan in 1968 and central Taiwan in 1979, respectively. These occurrences were separately caused by ingestion of rice oils contaminated with polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs) and polychlorinated quaterphenyls. The total intakes of PCBs and PCDFs by the patients were calculated to be, on the average, 633 and 3.4 mg for yusho, respectively, and 973 and 3.84 mg for yu-cheng, respectively, similar amounts of the causal agents being ingested in both instances. Increased eye discharge, pigmentation of nails, skin and mucous membrane, acneform eruptions and feeling of weakness were the most notable symptoms for both the poisonings. The PCB concentrations in the blood of patients were 1-30 ppb for yusho and 3-1156 ppb for yu-cheng five years and one year after the outbreaks, respectively. For the yusho patients, the clinical severity was closely related to the total amount of rice oil consumed and to the blood PCB concentration and the gas chromatographic pattern of blood PCBs.