Abstract
Individual blood samples obtained from yusho and yu-cheng patients who had been poisoned by ingesting contaminated cooking oils, from workers occupationally exposed to polychlorinated biphenyls (PCBs) and from unexposed individuals were analyzed for PCBs, polychlorinated quaterphenyls (PCQs) and polychlorinated dibenzofurans (PCDFs) by gas chromatography and mass spectrometry. PCBs were found in the blood of all samples. PCQs were detected in the blood of 54 of 56 living yusho patients 11 years after the outbreak, and in all yu-cheng patients 6 months following poisoning. These facts indicate that the presence of PCQs in the blood was a good mark of past ingestion of the toxic oil. In the yu-cheng cases, PCDFs as well as PCBs and PCQs were detected in all blood samples. These identified isomers have been reported to be remarkably highly toxic compounds, i.e., both the 2,3,7,8-tetrachlorinated and 2,3,4,7,8-pentachlorinated compounds are toxicologically hundreds to thousands of times more toxic than PCB. In view of the high toxicity of PCDFs found in the yu-cheng patients' blood, we must deduce that they are the primary causal agents of yusho as well as of the yu-cheng incident.