Abstract
The occurrence and fates of polychlorinated dibenzo‐p‐dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were investigated in two species of frog, mountain brown frog (Rana ornativentris) and Japanese brown frog (Rana japonica), and in soil samples. This study was carried out as part of an investigation aimed at determining the cause of extra forelimbs in the mountain brown frog. Frogs, not including malformed ones, and soil samples were collected at three sites in Kitakyushu, Japan, including the site where the malformed frogs were found and two reference sites. All samples were analyzed for PCDDs/PCDFs and coplanar PCBs. Relatively high concentrations of PCDDs/PCDFs and coplanar PCBs were detected in the soils and frogs collected from all three sites. Comparisons of concentrations in frogs and soils indicated that bioaccumulation of PCDDs/PCDFs was much lower than that of coplanar PCBs and that 2,3,7,8‐substituted PCDDs/PCDFs were more highly accumulated than non–2,3,7,8‐substituted isomers. From comparison of concentrations between the sexes, it was found that concentrations of dioxins, except for PCDDs, were significantly higher in males than in females. In the present study, relatively high concentrations of dioxins in frogs were found and maternal transfer to the eggs was strongly suspected. However, no difference in dioxin concentrations in frogs between the study site and the reference sites was found, so the cause of the malformations was not dioxins and remains unknown.