9-Octadecenedioic acid

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErL50 (72 h) > 100 mg/L for Pseudokirchneriella subcapitata (OECD 201), read-across with analogue substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2)
NOErC (72 h) = 45% of filtered solution prepared at a nominal loading rate of 100 mg/L for Pseudokirchneriella subcapitata (OECD 201), read-across with analogue substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2)
NOErLR (72 h) < 100 mg/L for Pseudokirchneriella subcapitata (OECD 201), read-across with analogue substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2)

Additional information

Since no studies investigating the toxicity of octadec-9-enedioic acid (EC 802-22-7) to algae are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2) was conducted. The source substance is representative to evaluate the toxicity of octadec-9-enedioic acid (EC 802-22-7) to algae.

Based on their chemical structure, both the target substance (Octadec-9-enedioic acid, EC 802-22-7) and the source substance ((Z)-9-Octadecen-1,18-dioic acid, CAS 20701-68-2), belong to the family of linear monounsaturated dicarboxylic acids. While the target substance contains a cis- and trans-isomer, the source substance consists of the cis-isomer.

This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

A GLP study according to OECD guideline 201 with the green alga (Pseudokirchneriella subcapitata) was performed with the analogue substance (Z)-9-Octadecen-1,18-dioic acid (CAS 20701-68-2), the cis-isomer of both of the stereo-isomers, under static conditions (Bogers, 2001c).

Following a limit test at a loading rate of 100 mg/L, green algae were exposed to 2.2, 4.5, 10, 22, 45, and 100% of a filtered test solution prepared at a nominal loading rate of 100 mg/L and an untreated control for 72 hours. The test solution was prepared by dissolving the test item in test medium followed by 4 hrs of stirring and filtering. No additional solvent was used.

Analytical monitoring of the test item concentrations during the test were not conducted. All effect concentrations were based on nominal test concentrations. Growth rates were in the range of the controls in the dilutions containing 2.2 to 45% of a filtered solution prepared at 100 mg/L during the 72-hour test period, whereas the growth rate of algae exposed to a 100% filtrate were increasingly reduced. Thus, the ErC50 and the NOErC were determined to be >100% and 45% of filtered solution prepared at a nominal loading rate of 100 mg/L, respectively. Therefore, the NOErL, LOErLR and ELr50 can be considered to <100, 100, and >100 mg/L, respectively.