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Toxicity to aquatic algae and cyanobacteria

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Description of key information

DPGDB:

Toxicity to aquatic algae and cyanobacteria:

- Key study, reliability 1, OECD 201, Pseudokirchneriella subcapitata - The EbC50 (biomass, 72 h) was 0.7 mg/L and the ErC50 (Growth rat,e 0 - 72 h) was 3.2 mg/L. The EbC50 (biomass, 96 h) was 0.62 mg/L and the ErC50 (Growth rate, 0 - 96 h) was 2.5 mg/L. The corresponding 72 hour and 96 hour "no-observed effect concentration" (NOEC) for biomass were 0.16 mg/L and <0.07 mg/L, respectively. The corresponding 72 hour and 96 hour "no-observed effect concentration" (NOEC) for Growth Rate were 0.68 mg/L and 0.27 mg/L, respectively.

DEGDB:

Toxicity to aquatic algae and cyanobacteria:

- Study in progress

- Disregarded study, reliability 3, OECD 201, Pseudokirchneriella subcapitata - The 72h EL50 (Area under the curve, biomass) was 5.2 mg/L and the 72h EL50 (Growth rate) was 11 mg/L. The corresponding "No-observed effect loading rate" (NOELR) were 2.2 mg/L and 1.0 mg/L, respectively. The 96h EL50 (Area under the curve, biomass) was 5.9 mg/L and the 96h EL50 (Growth rate) was 15 mg/L. The corresponding NOELR for both were 2.2 mg/L. Study endpoints were based upon nominal loading rates. Analytical measurement of the exposure solutions were made, however the final measurements were all at non-detect levels resulting in the geometric mean measured concentrations being unreliable. The study is being repeated.

Key value for chemical safety assessment

EC50 for freshwater algae:
3.2 mg/L
EC50 for marine water algae:
3.2 mg/L
EC10 or NOEC for freshwater algae:
0.68 mg/L
EC10 or NOEC for marine water algae:
0.68 mg/L

Additional information

This substance is a reaction mass of dipropylene glycol dibenzoate (DPGDB) and diethylene glycol dibenzoate (DEGDB). No testing has been performed on the reaction mass itself but data are available for DPGDB and DEGDB. All the studies were performed according to international test guidelines and in compliance with GLP. They are presented below, by component. The algal growth inhibition studies were performed on Selenastrum capricornutum (Pseudokirchnerella subcapitata). The substance was introduced using a water accommodated fraction (WAF) and the endpoints were reported using nominal loading rates. The exposure solutions in these studies were analytically measured at the beginning and end of the exposures. The studies were re-evaluated based upon the measured concentrations documented in the study reports. The study of DEGDB had final analytical measurements of the exposure solutions that were at non-detect levels and therefore the geometric means of the measured concentrations are belived to be unreliable. An algal test is being reconducted for this component of the reaction mass. The algal test of DPGDB provided analytical measurements of the exposure solutions that are believed to be reliable and the endpoints were recalculated based upon the geometric mean measured concentrations. All existing data suggest that the components of the reaction mass have quantitatively similar properties and the hazard assessment (PNEC derivation) for the reaction mass will be based upon a worst-case evaluation of data from the individual components. This endpoint for the reaction mass is currently fulfilled with the reliable study of the DPGDB component being representative of the reaction mass. However, an algal toxicity study is underway for DEGDB and this dossier will be updated with the results at completion.

The key values are:

Short-term toxicity to aquatic algae and cynaobacteria: EC50 = 3.2 mg/L (DPGDB 72 hour ErC50)

Long-term toxicity to aquatic algae and cynaobacteria: NOEC = 0.68 mg/L(DPGDB 72 hour NOEC growth rate)

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