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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Desmodesmus subspicatus_OECD 201: ErC50 (72h): 30 mg/L (extrapolated), ErC10 (72h): 2.4 mg/L, EbC50 (72h): 9.9 mg/L, EyC50 (72h): 5.2 mg/L, NOEC (72h): 0.39 mg/L
ECOSAR v1.11_green algae_Chronic Value (ChV): 70.44 mg/L (baseline toxicity)and 5.591 mg/L (SAR "Aliphatic Amines").

Key value for chemical safety assessment

EC50 for freshwater algae:
30 mg/L
EC10 or NOEC for freshwater algae:
2.4 mg/L

Additional information

The key study to evaluate the toxicity to aquatic algae and cyanobacteria of the substance was experimentally performed by Muckle (2013) according to OECD 201 and EU Method C.3. In addition, supporting information based on SAR (structure - activity relationship) estimations by ECOSAR v1.11 (EPIWIN software) is available (Chemservice S.A., 2018).

The acute toxicity to aquatic algae of n-Butylaminoethanol was tested according to OECD Guideline 201 and EU Method C.3 in a static freshwater test with Desmodesmus subspicatus (former name: Scenedesmus subspicatus) as test organism (Muckle, 2013). This key study is in compliance with GLP and was performed using five concentrations ranging from 0.1 to 10 mg/L nominal concentration. Incubation time was 72h. The cell concentration of each replicate was determined by measuring the absorption of the solutions at 440 nm every 24h with a spectral photometer. The cell density of the cultures was calculated based on the correlation curve between the adsorption and the cell density of the cultures determined by microscope counts. Growth rate µ, area under the growth curve (AUC) and the yield were determined from the cell densities at the respective observation times.

Significant inhibition of algal growth was observed at the nominal concentrations 1.0 mg/L, 3.2 mg/L and 10 mg/L. At each sampling date, the content of the test item in the test solutions was determined using HPLC-MS. The recovery after 72h was in a range between 103 % and 110 % of the measured start concentration. Therefore the test item can be stated as stable under test conditions. The measured concentrations were in a range between 106 % and 143 % of the nominal concentrations. Therefore the biological results were based on the geometric mean of the measured concentrations. The EC50 values of potassium dichromate (positive control) were tested in a separate reference test (GLP study no. 201206R301). The values lay within the normal range of the laboratory.

Based on the growth rate (72h), a NOErC of 0.39 mg/L, a LOErC of 1.2 mg/L, an ErC10 of 2.4 mg/L and an ErC50 of 30 mg/L (extrapolated) are reported. With regard to the AUC (72h, performed according to EU Method C.3), a NOEbC of 0.39 mg/L, a LOEbC of 1.2 mg/L and an EbC50 of 9.9 mg/L are determined. Based on the yield (72h), a NOEyC of 0.39 mg/L, a LOEyC of 1.2 mg/L and an EyC50 of 5.2 mg/L are reported.

The chronic toxicity to green algae of Butylaminoethanol was further predicted by the computer program ECOSAR v1.11 (EPIWIN software) by US-EPA (Chemservice S.A., 2018) as supporting information. An extensive set of structure – activity relationships (SARs) is utilized by the computer program, to predict the acute and chronic toxicity for three trophic levels for aquatic species, based on the neutral organics SAR (Baseline Toxicity). The mode of toxic action for most neutral organic chemicals is narcosis, and many chemical classes present toxicity to organisms via narcosis (i.e. ethers, alcohols, ketones). However, some organic chemical classes have been identified as having a more specific mode of toxicity. These are typically organics that are reactive and ionizable and that exhibit excess toxicity in addition to narcosis (i.e. acrylates, epoxides, anilines). Regarding long-term toxicity, the so-called Chronic Value (ChV) is predicted, which is defined as the geometric mean of the Lowest Observed Effect Concentration (LOEC) and the No Observed Effect Concentration (NOEC). It can just classify a substance according to a low, moderate or high toxicity concern. For the test substance concerning long-term toxicity to green algae a ChV(4d) of 70.44 mg/L is predicted for baseline toxicity and 5.591 mg/L applying the SAR "Aliphatic Amines", indicating a moderate toxicity concern. No GLP criteria are applicable for the usage of this tool, but due to the fact that it is a scientifically accepted calculation method the estimations performed are reliable with restrictions and can be used for the chemical safety assessment.