John Wiley & Sons, Ltd.

Bioavailability‐based chronic toxicity measurements of permethrin to Chironomus dilutus

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Compared to acute toxicity, chronic exposures to low levels of contaminants are more environmentally relevant but less data are available. Sediment toxicity of the pyrethoid permethrin to Chironomus dilutus was determined. The whole life cycle toxicity testing was conducted with the endpoints covering survival, growth, emergence and reproduction. Permethrin caused 50% lethality in C. dilutus at 1.83 ± 1.13 and 1.20 ± 0.55 µg/g organic carbon (OC) after exposures of 20 d (before pupation) and 58 d (the end of the testing), respectively. The 5% and median effect concentrations (EC5 and EC50) represented the marginal and toxic levels of the sublethal effects, respectively, and effect data were all normalized to the controls before probit analysis. The EC5 for growth, emergence and reproduction were 0.034 ± 0.006, 0.016 ± 0.008 and 0.009 ± 0.008 µg/g OC, respectively, while the respective EC50 were 1.09 ± 0.56, 0.838 ± 0.077 and 0.039 ± 0.100 µg/g OC. Additionally, a 24‐h Tenax extraction was employed to better assess permethrin bioavailability. Ultimately, response spectra with a series of endpoints were developed for permethrin using either OC‐normalized bulk sediment concentrations or bioavailability‐based Tenax extractable concentrations as the dose metric. The development of bioavailability‐based chronic toxicity endpoints for sediment‐associated permethrin would provide valuable benchmarks for evaluating ecological risk of this contaminant and contributing to improve sediment management policies. Environ. Toxicol. Chem. © 2013 SETAC

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