Organochlorine insecticides, polychlorinated biphenyls, and metals in water, sediment, and green frogs from southwestern Michigan

In an attempt to explain the etiology of frog deformities and population de clines, many possible causative factors have been examined, including the i nput of synthetic chemicals into aquatic systems, where frogs spend much of their lives, including their entire developmental stages. Deformities in p opulations of green frogs in wetlands of southwestern Michigan that are inf luenced by agricultural, urban, or industrial inputs were assessed in this study. Of the 1445 green frogs (Rana clamitans) examined, only four (0.3%) exhibited morphological deformities. This deformity rate is less than the r ecognized background level of deformities for this species, which is approx imately 1%. Concentrations of organochlorine insecticides, polychlorinated biphenyls (PCBs), and metals were determined in water, sediment, frog eggs, tadpoles, and adult green frog tissues. Concentrations of all individual o rganochlorine insecticides in tissue were less than 6 ng/g, wet wt. Concent rations of Sigma PCBs in tissue did not exceed 100 ng/g, wet wt. Concentrat ions of toxic metals were less than the limits of detection. Because no sig nificant numbers of green frog deformities were observed in this region, it can be assumed that at these low concentrations, physical malformations in green frogs should not be observed. Significance of study. This study provides information on the incidence of deformities in green frog populations in southwestern Michigan and offers b ackground data on chemical residues in green frogs and their environment. ( C) 2001 Published by Elsevier Science Ltd.