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Toxicity to microorganisms

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Description of key information

EC50 (6 h) > 10 mg/L (cell multiplication inhibition test with Pseudomonas putida according to Bringman and Kuehn (1980))

Key value for chemical safety assessment

Additional information

In accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to three structurally related category members pentaerythritol tetraesters of n-decanoic, n-heptanoic, n-octanoic and n-valeric acids (CAS 68424-31-7), decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (71010-76-9), and fatty acids, C8-10 (even numbered), di-and triesters with propylidynetrimethanol (CAS 11138-60-6) was conducted. This read-across is justified in detail in the overall summary (IUCLID chapter 6.1) and within the category 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 substances were used for the assessment. The fatty acid chain length of C5 – C10 of the first two read-across substances are similar to those of the target substance and both substances contain the same alcohol (pentaerythritol) and are tetra-esters. The remaining polyol ester category member has a different alcohol component (TMP) but chain lengths between C8 and C10.

The first study investigating the toxicity of read-across substance pentaerythritol tetraesters of n-decanoic, n-heptanoic, n-octanoic and n-valeric acids (CAS-No. 68424-31-7) to microorganisms was conducted as a cell multiplication inhibition test with Pseudomonas putida according to Bringman and Kuehn (1980) (Comber and Coleman, 1991). No inhibition on the growth was observed at the tested concentration (EC10 and EC50 (6h) > 10 mg/L (nominal)). The second read across study investigating toxicity to aquatic microorganisms was conducted with decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS 71010-76-9) under static conditions according to OECD 209 (Dickinson, 2008). In this study non-adapted activated sludge obtained from a domestic sewage treatment plant was used as inoculum. Test concentrations of 10, 100 and 1000 mg/L were prepared. Test substance was added directly to the test vessels. The test substance did not inhibit the respiration rate of activated sludge microorganisms at any of the concentrations employed in the test. Hence, the 3 h-EC50 was determined to be > 1000 mg/L based on the nominal test concentration. Therefore, it can be concluded that the test substance will not exhibit effects on the respiration rate of microorganisms.

The third read across study with decanoic acid, ester with fatty acids, C8-10 (even numbered), di-and triesters with propylidynetrimethanol (CAS 11138-60-6) was conducted according to OECD 209 investigating aquatic microorganisms (Kuttler, 1998). In this study activated sludge obtained from a domestic sewage treatment plant was used as inoculum. A test concentration of 10000 mg/L was prepared and was added directly to the test vessels. The test substance did not inhibit the respiration rate of activated sludge microorganisms, the 3 h-EC50 was therefore determined to be > 10000 mg/L based on the nominal test concentration. Therefore it can be concluded that the test substance will not exhibit effects on the respiration rate of microorganisms.

Based on these results from structurally related read-across substances which are characterized by a similar ecotoxicological profile, it can be concluded that reaction mass of Heptanoic acid 3-pentanoyloxy-2,2-bis-pentanoyloxymethyl-propyl ester, Heptanoic acid 2-heptanoyloxymethyl-3-pentanoyloxy-2-pentanoyloxymethyl-propyl ester and Heptanoic acid 3-heptanoyloxy-2-heptanoyloxymethyl-2-pentanoyloxymethyl-propyl ester (former CAS 68441-94-1) will not have adverse effects on the respiration rate of microorganisms, therefore, a disturbance in the biodegradation process of a sewage treatment plant is not anticipated. As it can be seen in the data matrix of the category justification in section 13 and the overall endpoint summary IUCLID 6.1, all reliable data in the polyol esters category support this hazard assessment by showing a consistent pattern of results, i.e. no microbial inhibition and no toxic effects were observed to aquatic organisms up to the limit of water solubility.