Chemical analysis and toxicity of polychlorinated biphenyls and dibenzofurans in relation to yusho

A typical lot of Kanemi rice oil ingested by patients with yusho (PCB poisoning) and the blood, liver and adipose tissue of the patients were analyzed for individual congeners of polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PCDFs) by gas chromatography and gas chromatography-mass spectrometry. The individual congeners identified were assayed for biological properties such as accumulation ability in the liver of monkeys and rats, inducing activities of benzo[a]pyrene 3-hydroxylase, benzphetamine demethylase and DT diaphorase in rats, and gravimetric changes of the thymus and liver in rats. Among the seven PCB congeners detected in yusho patients, 2, 3, 4, 5, 3', 4'-hexa-CB seems to be the most related compound to yusho by its strong effects on induction of the liver enzymes, and on atrophy of the thymus and hypertrophy of the liver in rats. PCDF congeners identified in the patients showed severe toxicity in rats than this PCB, exhibiting stronger enzyme induction and gravimetric changes of the tissues even at very low doses of 1-10 micrograms/kg. These PCDFs, especially 2, 3, 4, 7, 8-penta-CDF, were also very accumulative in the liver. Therefore, they are considered as the most important etiologic agents for current symptoms of yusho.