Persistence of dieldrin water and channel catfish from the Des Moines River, Iowa, 1971-73 and 1978

This study was conducted to determine if dieldrin concentrations in water and fish of the Des Moines River, Iowa, decreased after registration of the compound was withdrawn by the Environmental Protection Agency in 1975. Mean June concentrations of dieldrin in river water decreased from 50 ppt in 1971 to 11 ppt in 1978. Average daily transport of dieldrin was 156 g in 1971 and 70 g in 1978. July levels in channel catfish muscle were 75 ppb in 1973 and 46 ppb in 1978. Dieldrin was still present in significant concentrations in the aquatic system 3 years after registration withdrawal.