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Biodegradation in water: screening tests

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Description of key information

Readily biodegradable (BIOWIN v4.10); readily biodegradable: 71.9 - 99.8% (CO2 evolution) after 28 d (OECD 301B) (read-across)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Since no reliable studies investigating the ready biodegradability offatty acids, C8-10, tetraesters with pentaerythritol (CAS 85586-24-9)are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to structurally related category membersdecanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid(CAS 71010-76-9),fatty acids, C16-18 and C18-unsaturated, tetraesters with pentaerythritol(CAS 68604-44-4) andpentaerytritol tetraoleate(CAS 19321-40-5) was conducted. The read-across substances are characterized by the same alcohol component (pentaerythritol) tetra-esterified with similar fatty acids (C5-C10) or with longer fatty acids (C16 and C18) and can therefore be used for read-across – in the latter caseas worst case approachsince the chain length is the determining factor for biodegradation. The first step of biodegradation is the enzyme-catalysed cleavage of the ester bond by lipase or esterase which are synthesized by a wide range of microorganisms (Boczar et al., 2001). The free fatty acids (C4 to C24 incl. C18 unsatd.) are known to be degraded rapidly and utilized as substrates by activated sludge microorganisms (Kangala & Medrzycka, 2008). The first study was conducted with decanoic acid, mixed esters with heptanoic acid, octanoic acid, pentaerythritol and valeric acid (CAS 71010-76-9) (Febbo, 2006). This study was conducted according to OECD 301F (GLP) under aerobic conditions using fresh activated, non-adapted sludge from a municipal sewage treatment plant (STP) as inoculum. A test concentration of 50.2 mg/L (test material) was applied. A mean biodegradation of 84% based on O2 consumption was observed after 28 d. Since the substance reached the pass level for OECD 301F (biodegradation is > 60% after 28 d) the substance is stated to be readily biodegradable according to the OECD criteria.

The second study was conducted withfatty acids, C16-18 and C18-unsaturated, tetraesters with pentaerythritol(CAS 68604-44-4) according to OECD Guideline 301B under aerobic conditions using non-adapted activated sludge as inoculum (Häner, 2007). A test concentration of 22.8 mg/L (TOC) was applied. Based on CO2 evolution a mean biodegradation of 76% was observed after 28 days. Hence, the substance is determined to be readily biodegradable according to OECD criteria.

These results are supported by a third GLP-Guideline study with pentaerythritol tetraoleate (CAS-No. 19321-40-5) according to OECD 301B using non-adapted activated sludge as inoculum (Desmares-Koopmans, 1997). A test item concentration of 15.6 mg/L was applied. Based on CO2 evolution biodegradation was observed to be in the range of 71.9 to 99.8 after 28 days. Hence, the substance is determined to be readily biodegradable according to OECD criteria.

Moreover, an additional supporting study withfatty acids, C16-18, tetraesters with pentaerythritol (CAS 91050-82-7)was conducted according to the guideline CEC L-33 T 82, which investigates primary biodegradation (Falkenback & Vereecken, 1991). For the test period of 21 days a biodegradation > 95% was reported. Due to the non-standard guideline and the lack of detailed information on the test procedure, the reliability of this test cannot be properly assessed. Nevertheless, this study also supports the biodegradability of the test substance.

In addition, results from QSAR calculations (BIOWIN v4.10) for the main components offatty acids, C8-10, tetraesters with pentaerythritol (CAS 85586-24-9)indicate, that the substance is readily biodegradable (Hopp, 2011).

Based on the results from structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) and on the results from QSAR calculations for the main components it can be concluded thatfatty acids, C16-18, tetraesters with pentaerythritol (CAS 91050-82-7)is readily biodegradable according to the OECD criteria.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within CSR.

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