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PROCEDURES FOR THE DERIVATION OF EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: ENDRIN
Citation:
Impact/Purpose:
This document is intended to provide environmental managers with an assessment tool for determining if the pesticide endrin is present in freshwater and marine sediments at concentrations that are unlikely to cause adverse effects to resident organisms. The information will be useful for the Office of Water, Superfund, Regions, States, and Tribes as an aid in the conduct of contaminated sediment assessments.
Description:
Under the Clean Water Act, EPA and the States develop programs for protecting the chemical, physical, and biological integrity of the nation's waters. To support these programs, efforts are conducted to develop and publish equilibrium partitioning sediment benchmarks (ESBs) for selected pollutants. The ESBs and associated methodology provide a means to estimate the concentrations of a substance that may be present in the sediments (freshwater and marine), while still protecting benthic organisms such as worms, clams, and shrimp from the effects of that substance. In this document, we describe procedures to determine the concentration in sediment of the insecticide endrin that can be considered non-toxic or safe to benthic organisms. The document represents approximately 15 years of research and development by NHEERL scientists. For endrin, the ESBs based on the Water Quality Criterion values are 5.4 micrograms of endrin/gOC for freshwater sediments, and 0.99 micrograms/gOC for saltwater sediments. This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of the insecticide endrin in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for the varying biological availability of chemicals in different sediments and allows for the incorporation of the appropriate biological effects concentration. This provides for the derivation of benchmarks that are causally linked to the specific chemical, applicable across sediments, and appropriately protective of benthic organisms. EqP can be used to calculate ESBs for any toxicity endpoint for which there are water-only toxicity data; it is not limited to any single effect endpoint. For the purposes of this document, the Final Chronic Value (FCV) from the Water Quality Criterion (WQC) for endrin was used as the toxicity benchmark. This value is intended to be the concentration of a chemical in water that is protective of the presence of aquatic life. The ESBWQC is derived by multiplying the FCV by the chemical's KOC, yielding the concentration in sediment (normalized to organic carbon) that should provide the same level of protection in sediment that the FCV provides in water. For endrin, this concentration is 5.4 g endrin/gOC for freshwater sediments and 0.99 g/gOC for saltwater sediments. Confidence limits of 2.4 to 12 g/gOC for freshwater sediments and 0.44 to 2.2 g/gOC for saltwater sediments were calculated using the uncertainty associated with the degree to which toxicity could be predicted by multiplying the KOC and the water-only effects concentration. The ESBWQCs should be interpreted as chemical concentrations below which adverse effects are not expected. At concentrations above the ESBWQCs, effects may occur with increasing severity as the degree of exceedance increases. These benchmarks do not protect against additive, synergistic, or antagonistic effects of contaminants or bioaccumulative effects to aquatic life, wildlife, or human health.