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Ecotoxicological information

Sediment toxicity

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Description of key information

Sediment-water chironomid test (OECD218): EC50(28d) > 560 mg/kg - based on developmental rate / EC50(28d): 380 mg/kg, NOEC: 180 mg/kg - based on reduction in emergence

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:
380 mg/kg sediment dw
EC10, LC10 or NOEC for freshwater sediment:
180 mg/kg sediment dw

Additional information

The toxicity to sediment-water chironomid of the test substance was investigated according to OECD guideline 218 in a static mode with Chironimus riparius as test organisms, which are representative of a wide variety of natural habitats and can therefore be considered as important non-target organisms in freshwater ecosystems (Sewell and McKenzie, 2005).Following two preliminary range-finding test, four replicates of 20 larvae per concentration were exposed to formulated sediment spiked with test material at concentrations of 100, 180, 320, 560 and 1000 mg/kg (dry weight of sediment) for a period of 28 days. 600 mL glass beakers with approximately 8 cm in diameter were used. After the 2-day equilibration period the aeration was stopped and 20 larvae were placed in each test and control vessel and maintained in a temperature controlled room at approximately 21 °C with a photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods. The aeration was switched back on after approximately 24 hours having allowed the larvae to settle in the sediment. The larvae were fed at a rate of 0.5 mg Tetramin® flake food per larva per day. The Tetramin® flake food was prepared as a suspension in water and an appropriate volume added to the overlying water. The measured end-point for the test was the number of live, emerged adult midges. The number of emerged adult midges was recorded daily until termination of the study after 28 days. The sex of the individual midges was also determined after emergence. The male midges were identified

by the presence of plumose antennae and the female by the absence of plumose antennae. Any egg masses produced prior to termination were also recorded and removed fiom the test vessels to prevent re-introduction of larvae into the sediment. The number of visible pupae that failed to emerge were counted separately. Any abnormal behaviour was also recorded. The control group was maintained under identical conditions but not exposed to the test material. The EC50 (development rate) based on nominal test concentrations was greater than 560 mg/kg. Although significantly lower numbers of adult midges emerged at the concentration of 560 mg/kg, the rate at which they emerged was similar to that of the control, therefore the EC50 (development rate) was greater than 560 mg/kg. No adult midges emerged at 1000 mg/kg, therefore a calculated EC50 value could not be determined. The 28-Day EC50 (reduction in emergence) based on nominal test concentrations was 380 mg/kg with 95 % confidence limits of 300 - 490 mg/kg. The No Observed Effect Concentration (NOEC) was 180 mg/ kg. Analysis of the test sediments on Day -2, 0 and 28 showed the measured concentrations to range from 84 % to 119 % of nominal. Therefore it was considered justifiable to calculate the results based on nominal test concentrations only. The study is regarded as well-documented Guideline study with certificated GLP compliance and is therefore referred as "key study" without restrictions (Klimisch 1).