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Toxicity to soil microorganisms

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Description of key information

EC50 > 1000 mg/kg dw soil (OECD 216)

Key value for chemical safety assessment

Additional information

Since no studies investigating the toxicity to soil microorganisms of 2,2-bis[[(1-oxopentyl)oxy]methyl] propane-1,3-diyl divalerate (CAS 15834-04-5) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to structurally related category members was conducted. The read-across substance is 2,2-bis(hydroxymethyl)-1,3-propanediyl dioleate (CAS 25152-96-6), a pentaerythritol (mono – tri) ester with predominantly C18 unsatd. fatty acids. Supporting data investigating the toxicity to microorganisms are presented for tristearin (CAS 555-43-1), methyl oleate and for fatty acids of different chain length (C4-C18).

The study with 2,2-bis(hydroxymethyl)-1,3-propanediyl dioleate (CAS 25151-96-6) was conducted investigating the effects on nitrogen transformation according to OECD 216 is available (Simon, 2013). In this GLP study nominal test concentrations of 62.5, 125, 250, 500 and 1000 mg/kg dw were tested. The EC50 for the nitrogen transformation was calculated to be > 1000 mg/kg dw soil (the highest concentration tested). Therefore it can be concluded that the test substance will not exhibit effects to soil microflora.

This is supported by further evidence from literature data. This data showed that soil microorganism communities are well capable of degrading fatty acid esters (Hita et al., 1996 and Cecutti et al., 2002) and use them as energy source (Banchio & Gramajo, 1997). Hita et al. investigated the degradation of the model molecule tristearin which is a triglyceride containing of glycerin tri-esterified with stearic acid in three different soils for 4 weeks. The amount of stearic acid increased in considerable amounts during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. The investigation of ester fractions moreover showed the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) which were not determined in the controls. Nevertheless the amounts were no longer present after 4 weeks, which leads to the assumption that degradation by soil microorganisms had occurred. The same was shown by Cecutti et al. (2003). One soil sample was chosen and incubated with methyl oleate (plant oil) for 120 d. Methyl oleate and its metabolites were completely degraded after 60 d. Streptomyces coelicolor, a common gram-positive soil bacterium uses fatty acids (C4-C18) as sole carbon end energy source indicating that fatty acids are not-toxic and can be used for catabolism (Banchio and Gramajo, 1997). The available literature data shows that soil microorganisms are capable to break-up ester bonds and degrade fatty acids in significant amounts. Moreover, the data indicated the non-toxic properties of fatty acids since they can be used as energy source.

Therefore, one can conclude from all available data that toxicity to soil microorganisms is not of concern for PE esters.

 

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