P,p′-DDE bioaccumulation in female sea lions of the California Channel Islands

Abstract

An area of sediment on the Palos Verdes shelf and in Santa Monica Bay off Los Angeles, CA is contaminated with DDE and other breakdown products of DDT as a result of discharges of DDT through the Whites Point outfall. Elevated concentrations of DDE have been found in the water column of the Palos Verdes Shelf and in various fish species inhabiting the shelf and Santa Monica Bay. High concentrations have also been found in California sea lions from San Miguel Island and sea lion carcasses on Santa Catalina Island. These islands are located some distance from the Palos Verdes shelf and Santa Monica Bay. It was the purpose of this study to determine if it is likely that the Palos Verdes Shelf/Santa Monica Bay sediments were the principal source of the DDE in the Channel Island sea lions via a pathway from sediments to water and fish preyed on by sea lions. A time variable, age dependent, physiologically based toxicokinetic model of female California sea lions was developed. Mass and energy balance equations describe the uptake and loss of contaminants. The contaminants are partitioned among multiple body compartments, including lipid and non-lipid body tissue and milk. Contaminants are distributed into a fetus of females. Physiological and toxicokinetic data were used to establish rates of growth, respiration, reproduction and lactation, internal partitioning of DDE, efficiency of DDE uptake and rates of DDE excretion. The model was used to estimate the likely DDE exposure history of the sea lions in view of their DDE body burdens. Field-measured dietary composition and prey contaminant levels were then used to establish potential exposure to DDE from various regions within the Southern California Bight. Comparison of the estimated exposure history with that attainable from the various regions indicated that the more highly contaminated lactating females were exposed to prey at levels found only on the Palos Verdes Shelf and in Santa Monica Bay. Thus, it is likely that the sediments impacted by the Whites Point outfall were the source of much of the DDE and PCBs in these animals.