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Short-term toxicity to aquatic invertebrates

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Description of key information

There are three studies available on the short-term toxicity of benoxacor to aquatic invertebrates (Daphnia magna). All three studies are considered to be reliable, although two have restrictions. The lowest LC50 of 4.782 mg/L (Hamaker, 1986) has been selected as the key endpoint for the chemical safety assessment. 

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
4.782 mg/L

Additional information

Three studies of short-term toxicity of benoxacor to aquatic freshwater invertebrates using the waterflea (Daphnia magna) as test specimen have been performed.

In a laboratory trial (Drottar 1987b), daphnids were exposed to five concentrations of benoxacor ranging from nominal 6.48 to 50 mg/L in a static test design. This GLP-compliant study was performed to the EPA OPP 72-2 guideline and was considered to be reliable with restrictions (Klimisch 2), due to the fact that acetone was used as a co-solvent but the volume used was not reported. The 48-hour EC50 value was determined to be 11.47 mg/L and the NOEC was 4.74 mg/L. In a second test (LeLievre 1991b), benoxacor was studied at nominal concentrations ranging from 6.5 to 50 mg/L. The 48-hour EC50 value was calculated to be 17 mg/L. The NOEC value was below 8.2 mg/L. This study was GLP compliant and performed to the EPA OPP 72-2 guideline. This study was considered to be reliable without restrictions (Klimisch 1). An additional study (Hamaker, 1986) was performed to the ASTM 1980 guideline. The obtained 48-hour LC50 for benoxacor was of 4.782 mg/L. This study was considered to be reliable with restrictions (Klimisch 2), since no analysis had been performed to confirm initial nominal exposure concentrations or to confirm the stability of the substance under static exposure concentrations.

It is proposed that the lowest LC50 from the three available tests (4.782 mg/L, Hamaker, 1986) is selected as the key value for chemical safety assessment.