Bioavailability‐based chronic toxicity measurements of permethrin to Chironomus dilutus

Abstract

Compared with acute toxicity, chronic exposures to low levels of contaminants are more environmentally relevant, but fewer data are available. In the present study, 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 µg/g organic carbon (OC) and 1.20 ± 0.55 µg/g 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 EC5s for growth, emergence, and reproduction were 0.034 ± 0.006 µg/g OC, 0.016 ± 0.008 µg/g OC, and 0.009 ± 0.008 µg/g OC, respectively; the respective EC50s were 1.09 ± 0.56 µg/g OC, 0.838 ± 0.077 µg/g OC, and 0.039 ± 0.105 µg/g OC. In addition, 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.

Agricultural insecticides threaten surface waters at the global scale

“…2B) also signify remarkable environmental risks. Sediment samples reflect exposure conditions over longer time spans compared with those of water samples, and the high exceedance levels (i) support the data reported for water, (ii) are likely due to the high hydrophobicity of many insecticides, (iii) imply long-term (chronic) risks to sediment-dwelling organisms (23), and (iv) indicate that both major aquatic ecosystem components are at risk.…”

Assessment of Sediment Risk in the North End of Tai Lake, China: Integrating Chemical Analysis and Chronic Toxicity Testing with Chironomus dilutus

“…Meanwhile, a control sediment was collected from a drinking-water reservoir in Conghua, China. This sediment exhibited no chronic toxicity to the midges and contained no target contaminants at concentrations greater than the reporting limits (RLs) (Du et al 2013(Du et al , 2014.…”

“…Life-cycle toxicity tests using C. dilutus were performed in triplicate for each group according to a previously published method (Du et al 2013). In brief, the test was initiated from newly hatched midge larvae (\24 h old) and terminated on the hatch of the second generation.…”

Chronic Toxicity Thresholds for Sediment-Associated Benzo[a]pyrene in the Midge (Chironomus dilutus)

“…Sediment samples were sieved through a 2-mm sieve on site and transported to Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS), where they were sieved through a 500-lm sieve, homogenized, and stored at 4°C. Previous toxicity testing and analytical work showed that the control sediment had limited contamination and did not exhibit adverse effects to benthic organisms (Du et al 2013). After inorganic carbon was removed by 1 mol/l HCl solution, total OC content of the sediment was analyzed using an Elementar Vario EL III elemental analyzer (Hanau, Germany) with a value of 1.60 ± 0.14 %.…”

“…Three replicates were used for each group. Specific end points used are listed in Table 2, and the evaluation of toxic end points followed the methods reported in our previous study (Du et al 2013). …”