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Sediment toxicity

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Description of key information

28 day EC50: >56 mg/kg sediment dry weight; NOEC: 56 mg/kg sediment dry weight: LOEC: >56 mg/kg sediment dry weight; emergence of Chironomus riparius.

28 day EC50: >56 mg/kg sediment dry weight; NOEC: 10 mg/kg sediment dry weight; LOEC: 17 mg/kg sediment dry weight; development of Chironomus riparius.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
10 mg/kg sediment dw

Additional information

A 28 day EC50 value of >56 mg/kg sediment dry weight, a NOEC value of 56 mg/kg sediment dry weight and a LOEC value of >56 mg/kg sediment dry weight (highest concentration tested) based on mean measured concentrations have been determined for the effects of the test substance on emergence of Chironomus riparius, in accordance with OECD Guideline 218.

A 28 day EC50 value of >56 mg/kg sediment dry weight (highest concentration tested), a NOEC value of 10 mg/kg sediment dry weight and a LOEC value of 17 mg/kg sediment dry weight based on mean measured concentrations have been determined for the effects of the test substance on development of Chironomus riparius in accordance with OECD Guideline 218.

The author notes that the midge emergence development rate NOEC with measured concentrations is slightly lower than the calculated M4Q sediment solubility limit of 15 mg/kg-dw. The Lowest-Observed-Effect Concentration (LOEC) for midge emergence and combined midge development rate, based on the mean measured concentrations of applied test substance, was established to be >56 and 17 mg/kg, respectively. As the midge development LOEC value is approximately equivalent to the calculated M4Q sediment solubility limit of 15 mg/kg-dw, physical deposition of the chemical in sediment may be adversely affecting midge development.

The parent substance will strongly adsorb to organic matter, which may limit any hydrolysis. The sediment organisms are therefore more likely to have been exposed to the parent substance rather than the hydrolysis products, even though the test substrate was not renewed during the test.