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An overview of the refinements and improvements to the USEPA’s sediment toxicity methods for freshwater sediment
Citation:
Norberg-King, T., R. Hockett, C. Ingersoll, AND Dave Mount. An overview of the refinements and improvements to the USEPA’s sediment toxicity methods for freshwater sediment. SETAC Europe, Rome, ITALY, May 13 - 17, 2018.
Impact/Purpose:
Sediment toxicity tests are used for contaminated sediments, chemical registration, and water quality criteria evaluations and can be a core component of ecological risk assessments at contaminated sediments sites. With USEPA’s test method guidance document recently revised, the updated procedures for assessing the toxicity and bioaccumulation testing of freshwater sediments are improved for risk assessment. Each test method has updated guidance for the starting size/age of organisms, diets and rations, reconstituted water changes, modifications to the test acceptability control survival, weight and other endpoints and each of these methods is also readily adapted for waterborne exposures.
Description:
Sediment toxicity tests are used for contaminated sediments, chemical registration, and water quality criteria evaluations and can be a core component of ecological risk assessments at contaminated sediments sites. Standard methods for conducting sediment toxicity tests have been established by USEPA, ASTM, Environment Canada and OECD. Revisions to USEPA’s Methods for Measuring the Toxicity and Bioaccumulation of Sediment-Associated Contaminants with Freshwater Invertebrates is planned for 2018. USEPA’s manual describes toxicity and bioaccumulation testing of freshwater sediments with 3 freshwater species, Hyalella azteca (amphipod), Chironomus dilutus (midge) and Lumbriculus variegatus (oligochaete) and 5 sediment toxicity test methods: 10-d tests with H. azteca and C. dilutus; a 42-d life-cycle test with H. azteca; a 50-d life-cycle test with C. dilutus and a 28-d bioaccumulation test with L. variegatus. While laboratories routinely met test acceptability criteria (TAC) for short-term sediment toxicity exposures (10-d control survival and ash-free-dry weight), laboratories reported variable biological performance with the longer exposures. With input from both midge and amphipod workgroups, each test method has updated guidance for the starting size/age of organisms, diets and rations, reconstituted waterchanges, modifications to the test acceptability control survival, weight and other endpoints. Control waters needs to have a minimum level of chloride and bromide and use of a sand substrate control to evaluate water and diet used in sediment testing included. While designed for sediment evaluations, the methods are readily adapted for waterborne exposures. For the oligochaete bioaccumulation test, the recommendation for the maximum loading rate is increased to 1 g dry tissue:100 g of sediment organic carbon (previously 1:50). Use of laboratory proficiency criteria is incorporated in addition to test acceptability criteria for individual tests for each species and method, laboratories would report their averages for the test endpoints/measures. These proficiency criteria would not be used to accept or reject individual tests, but serve as a broad indicator of laboratory performance and possibly provide insight where refinements are needed. In this talk, we will focus on the testing methods and improvements that have been made in each method for USEPA and ASTM methods. This abstract does not necessarily reflect the views or the policies of the USEPA.