Development and application of freshwater sediment-toxicity benchmarks for currently used pesticides

• Published in: The Science of the total environment Vol. 550; pp. 835 - 850
• Main Authors: Nowell, Lisa H., Norman, Julia E., Ingersoll, Christopher G., Moran, Patrick W.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-04-2016
• Subjects: Amphipoda; Animals; Benchmarking; Chironomus; Environmental Monitoring - methods; Environmental Monitoring - standards; Fresh Water - chemistry; Geologic Sediments - chemistry; Hyalella azteca; Mixtures; Pesticides - standards; Pesticides - toxicity; Sediment benchmarks; Sediment toxicity; Spiked-sediment bioassay; Toxicity Tests; Water Pollutants, Chemical - standards; Water Pollutants, Chemical - toxicity; USA; TU; EqP; PECQ; OPP; Spiked-sediment bioassay; SPME; Sediment benchmarks; EC50; EC10; TEBint; MATC; PWG; LEBeqp; TEBQ; LEBQ; USGS; PCB; TEBssb; Hyalella azteca; msPAF; Sediment-PTI; NOEC; ERL; EC25; ERM; LOEC; PTI; Mixtures; LEBcd; USEPA; TEBcd; OC; ESB; SETAC; Chironomus; Sediment toxicity; CA; Koc; MOA; SSB; LEBssb; LEB; TEBha; LEBha; PEC; DER; TEB; LC50; TEBeqp; Kow; TEC; PAH; LEBint; EC20; NAWQA
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.01.081

Sediment-toxicity benchmarks are needed to interpret the biological significance of currently used pesticides detected in whole sediments. Two types of freshwater sediment benchmarks for pesticides were developed using spiked-sediment bioassay (SSB) data from the literature. These benchmarks can be used to interpret sediment-toxicity data or to assess the potential toxicity of pesticides in whole sediment. The Likely Effect Benchmark (LEB) defines a pesticide concentration in whole sediment above which there is a high probability of adverse effects on benthic invertebrates, and the Threshold Effect Benchmark (TEB) defines a concentration below which adverse effects are unlikely. For compounds without available SSBs, benchmarks were estimated using equilibrium partitioning (EqP). When a sediment sample contains a pesticide mixture, benchmark quotients can be summed for all detected pesticides to produce an indicator of potential toxicity for that mixture. Benchmarks were developed for 48 pesticide compounds using SSB data and 81 compounds using the EqP approach. In an example application, data for pesticides measured in sediment from 197 streams across the United States were evaluated using these benchmarks, and compared to measured toxicity from whole-sediment toxicity tests conducted with the amphipod Hyalella azteca (28-d exposures) and the midge Chironomus dilutus (10-d exposures). Amphipod survival, weight, and biomass were significantly and inversely related to summed benchmark quotients, whereas midge survival, weight, and biomass showed no relationship to benchmarks. Samples with LEB exceedances were rare (n=3), but all were toxic to amphipods (i.e., significantly different from control). Significant toxicity to amphipods was observed for 72% of samples exceeding one or more TEBs, compared to 18% of samples below all TEBs. Factors affecting toxicity below TEBs may include the presence of contaminants other than pesticides, physical/chemical characteristics of sediment, and uncertainty in TEB values. Additional evaluations of benchmarks in relation to sediment chemistry and toxicity are ongoing.
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•Sediment-toxicity benchmarks are developed for 129 pesticides in whole sediment.•Benchmarks can be used to predict or interpret pesticide toxicity in whole sediment.•Benchmarks are based on spiked-sediment bioassays or equilibrium partitioning.•Benchmarks correctly predicted amphipod toxicity in 74% of samples in a case study.•Whole-sediment benchmarks may not always represent bioavailable concentrations.