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Short-term toxicity to aquatic invertebrates

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Description of key information

24h-EC50 > 100 mg/L (nominal)
24h-EC50 > 0.078 mg/L (limit water solubility)
24h-EC50 > 1000 mg/L (saturated solutions, nominal)

Key value for chemical safety assessment

Additional information

The acute toxicity of ethyl 3,5 -dichloro-4 -hexadecyloxycarbonyloxybenzoate (AF-366) to aquatic invertebrates was investigated in a study by Adema (1989) on Daphnia magna. This test was conducted according to OECD Guideline 202, under GLP conditions. Test concentrations of 1, 10 and 100 mg/L (nominal) were prepared applying a solvent (TBA, 1 mL/L) and 20 daphnids per concentration were exposed for 24 hours within a static water regime. Additionally, two saturated solutions without vehicle (one filtered and one unfiltered) were included in the experimental set up (1000 mg/L, nominal). Analytical measurements of actual test concentrations were not performed.

After 24 hours, only 4 daphnids were recorded immobile, 2 of them in the 100 mg/L treatment group and 2 in the unfiltered saturated solution. Microscopical inspections lead to the observation of a white substance (probably the test substance) in the gut of these organisms. Therefore, the observed effects are probably physical, rather than related to toxicity, and the 24h-EC50 was determined to be > 100 mg/L (nominal).

The test was conducted for 24 hours instead of the current standard 48-hours duration period. Due to the low solubility of the substance in water (0.078 mg/L), considerable difficulties were observed when preparing the test solutions. From the start of the test, precipitation of the substance (cloudiness) was observed at the highest tested concentrations and the unfiltered saturated solution. This state could not be avoided by using a solvent. Therefore, conducting a new test (even a semi-static test) does not seem justified, since no improvement in the results would be expected. Furthermore, no toxic effects were observed during the test or in the other two acute tests performed with aquatic organisms (fish, Adema, 1989; algae, Bruns, 2003).

Based on the available information, AF-366 is not considered to be acutely toxic to aquatic invertebrates within the range of its water solubility (≤ 0.078 mg/L).