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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

OECD Guideline 203, GLP, key study, validity 2:

Acute toxicity to fish: LC50(96h) > 100 mg/L

Key value for chemical safety assessment

LC50 for freshwater fish:
100 mg/L

Additional information

To assess the short-term toxicity of the registered substance to fish, three studies are available.

A study (DHI, 2002) was performed to assess the acute toxicity of the test item to Danio rerio,under semi-static conditions according to OECD Guideline 203: the test item appeared as white creamy liquid and it caused no mortality in the tested concentrations (0.1, 0.3, 1.0, 3.0 and 10 mg/L) during the 96 hour period. Under the test conditions, the 24, 48, 72 and 96 h LC50 value was higher than 10 mg/L (nominal concentration) and no mortality was observed in fish up to 10 mg/L (the maximum concentration tested). This study was considered as a supporting study of reliability 2. The second reliable study was performed by Sewell (1993) to assess the acute toxicity of the test item to rainbow trout Oncorhynchus mykiss,according to OECD Guideline 203. There were no mortalities or other adverse reactions to exposure in 20 fish exposed to a test concentration of 100 mg/L for a period of 96 hours. Highest test concentration resulting in 0% mortality is ≥ 100 mg/L. This study was considered as a key study of reliability 2.

The third study from Boer (1990) assessed the acute toxicity of the test item to Poecilia reticulata similarly to OECD Guideline 203. Under the test conditions, the 24, 48, 72 and 96 h LC50 value was > 10 to < 18 mg/L (nominal concentration). No effects were found in this study up to a concentration of 5.6 mg/L at 96 h. No indications are provide of how test solutions were prepared and whether they were clear. The mortality oberved in this study at concentrations >5.6 mg/L are considered to be in strict contrast with the two other fish studies where no mortality was observed at 10 mg/L (maximum concentration tested) and 100 mg/L. Moreover, no effects were observed on other species either. An explanation for this was therefore sought:

Studies on fish (DHI, 2002), daphnia (Adema, 1980) and algae (SafePharm,2003) included in this dossier report that the solutions with akypoquat 131 appear as white creamy liquid between 0.1 and 10 mg/L (fish test), whitish turbid from 0.32 to 320 mg/L (daphnia) and very slightly cloudy with homogenous dispersions at 100 mg/L (algae). Based on these observations, the critical micelle concentration is expected to be lower than 10 mg/L. This is supported by a specific study on CMC of the registered substance where this value was determined as <1 mg/L. It is generally considered that effects of surfactants at concentrations greater than the CMC should be treated with caution as bioavailability of the test substance does not increase beyond this concentration and there is a risk of physical effects. As a consequence the no effect concentrations up to a value of 5.6 mg/L observed in the third study (Boer, 1990) should be considered while the LC50 (96h) > 10 to < 18 mg/L (nominal concentration) from this study should be disregarded as >CMC and due to physical effects.