Comparative rates of elimination of some individual polychlorinated biphenyls from the blood of PCB-poisoned patients in Taiwan.

In 1979, a mass outbreak of poisoning occurred in Central Taiwan due to the ingestion of rice-bran oil contaminated with polychlorinated biphenyls (PCBs). The major PCB isomers and congeners in the toxic rice oil and in the blood of PCB-poisoned patients were characterized by gas chromatography and gas chromatography/mass spectrometry using a highly efficient glass capillary column. The elimination of some major individual PCBs from blood of these patients was studied. The results indicate that tetra- and pentachlorobiphenyls with adjacent unsubstituted carbon atoms at meta-para positions are rapidly eliminated from the blood of patients, while PCBs with the same degree of chlorination but with adjacent unsubstituted carbon atoms at ortho-meta positions are eliminated more slowly. The results also indicate that most of the hexa- and heptachlorobiphenyls, with adjacent unsubstituted carbon atoms at ortho-meta positions of the biphenyl ring, are eliminated very slowly. Laboratory-animal studies have indicated that PCB excretion depends primarily on the rate of metabolism; therefore these differences in rates of elimination of PCBs should reflect the differences in their rates of metabolism.