Isomer‐specific determination and toxic evaluation of potentially hazardous coplanar PCBs, dibenzofurans and dioxins in the tissues of “Yusho” PCB poisoning victim and in the causal oil

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Abstract
In the light of new discoveries on the extremely toxic non‐ortho coplanar 3,3’,4,4'‐tetra‐ (T4CB), 3,3’,4,4’,5‐penta‐(P5CB) and 3,3'4,4’,5,5'‐hexachlorobiphenyl (H6CB) and their mono‐ and di‐ortho analogs, tissue samples of a Yusho poisoning victim and Yusho causal oils were subjected to a thorough congener/isomer‐specific investigation for polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated dibenzo‐p‐dioxins (PCDDs). Among the many PCB congeners detected in Yusho oil, non‐ortho coplanar T4CB constituted 3.1%, P5CB‐0.17% and H6CB‐0.0072% in total PCBs. Their concentrations in liver and adipose tissue were 130–700 (T4CB), 54–720 (P5CB) and 50–380 (H6CB) pg/g on wet weight basis. The observed concentrations in adipose tissue were two to four fold higher than that detected in unexposed individuals. Among the PCDFs identified, toxic 2,3,7,8‐substituted isomers including 2,3,4,7,8‐P5CDF were the dominant ones. Tetra‐ through hepta‐CDDs were detected in the oil, whereas octa‐CDD was the dominant isomer in the patient. A comparison with KC‐400 revealed enrichment of coplanar PCBs in Yusho oil along with toxic PCDFs. Enrichment was highest for 3,3'4,4'5,5'‐H6CB followed by 3,3’,4,4'5‐P5CB. A comparative toxic evaluation of these chemical groups in Yusho patient's adipose tissue based on “2,3,7,8‐T4CDD Toxic Equivalent Analysis” revealed accountable toxic contribution from coplanar PCBs. This analysis also confirmed that 2,3,4,7,8‐P5CDF was the principal causative agent in Yusho poisoning.

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