Disodium adipate

Toxicity to aquatic algae and cyanobacteria

Description of key information

Concerning the toxicity to algae, results from the corresponding acid, adipic acid are taken into account for this endpoint due to the absence of data for disodium adipate. The fresh water alga Pseudokirchnerella subcapitata was exposed to adipic acid for 72 hours. The experiment was conducted according to OECD Guideline 201 (Alga, Growth Inhibition Test). The test gave a 72-h EC50 value for effects on growth rate of 59 mg/L and a 72-h NOEC of 41 mg/L (MITI, 1997).

Key value for chemical safety assessment

EC50 for freshwater algae:

59 mg/L

EC10 or NOEC for freshwater algae:

41 mg/L

Additional information

Based on the absence of data, a read-across approach with adipic acid is applied. In aqueous media, disodium adipate and adipic acid acid dissociate into the corresponding anion (1,6-hexandioic acid ion) and the sodium ion and hydrogen ion (proton), respectively. Fate, behavior and the ecotoxicological properties of adipic acid and its disodium salt are thought to be an effect of the di-carboxylate ion rather than of the sodium ion or the hydrogen ion (proton), which are normal constituents in environmental systems and have no relevant ecotoxic properties in low concentrations. Therefore a read-across between disodium adipate and adipic acid is justified.

Preparing the SIDS-dossier within the scope of the ICCA/HPV-program the study conducted by the National Institute of Technology and Evaluation, Japan was not available. The following study was not taken into account.

Toxicity to algae was assessed using effect concentration relating to biomass obtained in a study conducted to the EU-method C.2. According to the Guidance on information requirements and chemical safety assessment R.7b (ECHA, 2012) results based on the biomass should not be used for assessment since biomass results depend on the growth rate of the species as well as the test duration and other elements of the test design. Thus, the presented result was scored as not reliable. Reconsiderations results in an 72-h EC50 of 39.8 mg/l and an 72-h EC10 of 14 mg/l.

This study on aquatic algae was characterized by a concentration-dependant decrease of pH. At the end of the 72-hour exposure period, the pH in the control treatment was 10.1, whereas it decreased from 8.2 to 5.4 in the range of concentrations (31.3 - 62.5 mg/L) covering the EC50 value (39.8 mg/L). Furthermore, it should be noticed that the pH value in the control treatment is high compared to the guideline's requirements. Based on this observation, a pH effect cannot be ruled out when considering the toxicity reported in this study.

Describing the toxicity towards aquatic algae, the study conducted by the National Institute of Technology and Evaluation, Japan

is preferred, despite deficiencies in study documentation concerning pH.