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Toxicity to aquatic algae and cyanobacteria

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Description of key information

No effects up to the limit of water solubility (OECD 201).

Key value for chemical safety assessment

Additional information

Since no studies are available investigating the toxicity of fatty acids, tall-oil, triesters with trimethylolpropane (CAS 94581-09-6) to aquatic algae are available for this endpoint, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally related source substances fatty acids, C16-18 and C18 unsatd., triesters with trimethylolpropane (CAS 68002-78-8), Fatty acids, C16-18 (even numbered) and C16-18-unsatd. (even numbered), triesters with trimethylolpropane (CAS 68002-79-9), 2-ethyl-2-(((1-oxoisooctadecyl)oxy)methyl)-1,3-propanediyl bis(isooctadecanoate) (CAS 68541-50-4) and fatty acids, C16-18 and C18-unsatd., branched and linear ester with trimethylolpropane (CAS 403507-18-6) was conducted. 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.

The first study with the read-across substance fatty acids, C16-18 and C18-unsatd., triesters with trimethylolpropane (CAS 68002-78-8) was conducted in compliance with OECD guideline 201 (Bouillon, 2012). Pseudokirchneriella subcapitata was used as test organism. The test solutions were prepared by using the water accommodated fraction (WAF) of the test substance concentration of 110 mg/L (nominal). After 72 h an EL50 > 110 mg/L (nominal) was determined based on growth rate.

The second study with the read-across substance fatty acids, C16-18 (even numbered) and C16-18-unsatd. (even numbered), triesters with trimethylolpropane (CAS 68002-79-9) was conducted as a limit test with a nominal Water Accommodated Fraction (WAF) of 100 mg/L (Scheerbaum, 2005). The static algal growth inhibition test with Desmodesmus subspicatus according to OECD 201 determined an ErL50 (72 h) > 100 mg/L after 72 h based on growth rate.

The third study with the read-across substance 2-ethyl-2-(((1-oxoisooctadecyl)oxy)methyl)-1,3-propanediyl bis(isooctadecanoate) (CAS 68541-50-4) was performed according to ISO 8692 using Scenedesmus subspicatus as test organisms (Marshall, 1996). The test period was 72 h and substance concentrations were measured at the start and the end of the exposure time. Based on the algal growth rate an EC50 (72 h) > 3.7 mg/L (measured) was determined.

The fourth study with the read-across substance fatty acids, C16-18 and C18-unsatd., branched and linear ester with trimethylolpropane (CAS 403507-18-6) was performed according to OECD 201 (GLP) using the freshwater algae Desmodesmus subspicatus (Vryenhoef and McKenzie, 2004). Algae were exposed to a nominal limit concentration of 0.2 mg/L prepared in acetone. This concentration reflects the maximum concentration soluble in water. Preliminary experiments which are documented in the study report showed that higher concentrations lead to turbid test solutions which may affect the outcome of the study (e.g. physical effects by insoluble particles). The test substance concentration was verified analytically by HPLC/UV-Vis. After an exposure of 72 h no inhibition of growth was observed neither in the treatment nor in the solvent and test medium control resulting in an EC50 (72 h) of > 0.2 mg/L (nominal) and > 0.056 mg/L (meas. TWA). A NOEC (72 h) of 0.2 mg/L (nominal) and 0.056 mg/L (measured) was derived.

Based on the available experimental studies from four structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that fatty acids, tall-oil, triesters with trimethylolpropane (CAS 94581-09-6) will not exhibit short-term effects on aquatic algae up to the limit of water solubility.