The finding of chlorinated dibenzofurans in a Japanese polychlorinated biphenyl sample

Summary Chlorinated dibenzofurans, including 1 ppm of tetrachlorinated dibenzofuran(s), and pentachloronaphthalene have been identified by combined gas chromatography/mass spectrometry in a polychlorinated biphenyl of Japanese manufacture (KC-400). The question of whether chlorinated dibenzofurans in KC-400 may have contributed to the reported Yusho incident is thus raised.