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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Readily biodegradable:  75.7% (CO2 evolution) after 26 d (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One study, investigating the ready biodegradability of former CAS 68441-94-1 was conducted according to OECD 301B (CO2 Evolution Test) using domestic activated sludge (non adapted) as inoculum (Bouillon and Defleur, 1999). A test concentration of 20 mg/L (TOC) was applied. A mean biodegradation of 75.7% based on O2 consumption was observed after 26 d. Within the 10-day time window the 60% level was not passed, nevertheless according to Annex I to the OECD Guideline for Testing of Chemicals ‘Revised introduction to the OECD guidelines for testing of chemicals, section 3’ (OECD, March 2006), the 10-day window should not be considered for this UVCB substance and due to a degradation of >60 % within 28 days the monomeric acids of sub-category 1 can be regarded as readily biodegradable.

In accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to structurally related category member pentaerythritol tetraesters of n-decanoic, n-heptanoic, n-octanoic and n-valeric acids (CAS 68424-31-7) and fatty acids, C16-18 and C18-unsaturated, tetraesters with pentaerythritol (CAS 68604-44-4) was conducted to support the above findings. 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 case as worst case approach since 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). In the first study conducted with CAS 68424-31-7 the biodegradation was tested in a CO2 Evolution Test according to OECD 301B using domestic activated sludge (non adapted) as inoculum (Häner, 2006). At test termination after 28 days Häner observed a mean degradation of 96% and the 10-day-window was reached even though this is a UVCB substance and thus consist of constituents with different chain-lengths, hence sequential (instead of concurrent) biodegradation can take place. Thus, the read across-substance is readily biodegradable according to OECD criteria. The second read across study was conducted with fatty acids, C16-18 and C18-unsatd., 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 further GLP-Guideline study according to OECD 301B with pentaerythritol tetraoleate (CAS-No. 19321-40-5) 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.

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 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 is readily biodegradable according to the OECD criteria.