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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

ErC10 freshwater algae = 22 mg/L
ErC50 freshwater algae = 82.5 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
82.5 mg/L
EC10 or NOEC for freshwater algae:
22 mg/L

Additional information

For the data endpoint toxicity to aquatic algae and cyanobacteria data are available for the read across substance CAS 577 -11 -7 (Docusate Sodium) . Due to the longer C-chain-length of CAS 577-11-7 when compared to the registered substance and a tendency of decreasing ecotoxicity with decreasing C-chain length this is considered as a conservative substance for read across.

For the data endpoint “Toxicity to aquatic algae and cyanobacteria” 2 experimental studies are available: 1 Klimisch 2 key-study and 1 disregarded Klimisch 3 study.

The study from Elementis (Scholz 1993) was classified as Klimisch 2 key study. In this study the growth inhibition of formulated product (which contains 64.2% Docusate Sodium) to Scenedesmus subspicatius was determined in a 72 h static GLP algae growth inhibition test. The test design was based on the EWG 88/302 guideline which is similar to the EEC C.1 guideline. The nominal test concentrations were 0 (control), 10, 17, 30, 50, 90 and 150 mg formulated product/L, corresponding to 0 (control), 6.42, 10.91, 19.26, 32.10, 57.78 and 96.30 mg Docusate Sodium/L. Eight control replicates and 5 replicates from each test solution were set up. Dose verification analysis was not performed. In order to determine the growth of the cultures, the optical density was measured by photometry at 685 nm. The cell density was calculated using a calibration curve (not provided in the report). The cell density was determined at 0, 24, 48 and 72 hours. The growth of the control cultures fulfilled the validity criteria from OECD 201 (2006). The 72 -hour ErC10 and ErC50 are 22 and 82.5 mg Docusate Sodium/L based on the nominal concentration. This study is considered to be acceptable for the risk assessment despite minor shortcomings in the reported documentation. Criticism points are the lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

In addition to the Klimisch 2 study, there is one Klimisch 3 study for toxicity to aquatic algae and cyanobacteria available. Due to the poor reliability of this study, it is disregarded and not discussed here.

The ErC50 value of the key study from Elementis (Scholz 1993) is 82.5 mg Docusate Sodium/L. The ErC50 value of the disregarded study from Cognis (Rieche 1994), i. e., 127 mg Docusate Sodium/L, is considered to be less reliable since the validity criteria of the OECD 201 (2006) were not met. Furthermore, the results of the key study are more protective than the results from the disregarded study. The ErC10 and ErC50 of 22 and 82.5 mg Docusate Sodium/L, respectively, are considered to be reliable and will be used for the further risk assessment of the registered substance.

The tests were performed with the read across substance CAS 577 -11 -7 (Docusate Sodium). Due to the longer C-chain-length of CAS 577 -11 -7 when compared to substance registered with this dossier and a tendency of decreasing ecotoxicity with decreasing C-chain length this is considered as a conservative substance for read across. A more detailed read across argumentation is provided in a separate document. Therefore, the results of these studies are considered to be reliable with restrictions for the risk assessment of the substance registered with this dossier.