3,7-dimethylocta-2,6-dienyl acetate

Biodegradation in water: screening tests

Description of key information

Neryl acetate multi is readily biodegradable based on read-across from Geranyl acetate, which is readily biodegradable in a study performed according to OECD TG 301F.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

The biodegradability in water is assessed based on read-across to Neryl acetate multi from Geranyl acetate. The executive summary of the source information is presented below, followed by the read-across rationale.

Geranyl acetate ready biodegradability

The biodegradation potential of Geranyl acetate was examined in a study according to OECD TG 301F, and in compliance with GLP criteria. In this biodegradation screening study, test substance at a concentration of 100 mg/L (267 mg/L based on ThOD) was inoculated with fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage for 28 days. Oxygen consumption was continuously recorded and biodegradation calculated as biological oxygen demand (BOD) as compared to theoretical oxygen demand (ThOD). A reference control (100 mg/L sodium benzoate), and a toxicity control (100 mg/L test substance with 100 mg/L sodium benzoate) were performed in parallel. The test is valid.

The reference control sodium benzoate was biodegraded >80% after 7 days, the toxicity control showed the test substance to be not toxic to the sludge micro-organisms. The test substance was biodegraded 85% after 28 days under the conditions of the test. Biodegradation started on day 1 and reached 66% at the end of the 10-day window (days 1 to 11) and therefore the 10-day window criterion was met. based on these findings, the test substance should be regarded as readily biodegradable according to this test.

Biodegradation of Neryl acetate multi based on read across from data available for Geranyl acetate (CAS# 105-87-3).

 

Introduction and hypothesis for the analogue approach

Neryl acetate multi is a multi-constituent of Neryl acetate and Geranyl acetate, which are the Z and E-isomers of each other. This ester has an unsaturated branched alkyl backbone to which an acetate group is attached. For this substance there is no experimental biodegradation data available. In accordance with Article 13 of REACH, lacking information can be generated by other than experimental testing means, i.e. applying alternative methods such as QSARs, grouping and read-across. For assessing the biodegradability of Neryl acetate multi, the analogue approach is selected because for one of the two main constituents, Geranyl acetate, experimental data is available which can be used for read across.

Hypothesis: Neryl acetate multi has the same biodegradation potential as Geranyl acetate based on similar bioavailability for micro-organisms and similar biodegradable groups.

Available information: Geranyl acetate is readily biodegradable in an OECD TG 301F, Rel. 1. The test concentration was 100 mg/l. The test substance was biodegraded 85% after 28 days under the conditions of the test. Biodegradation started on day 1 and reached 66% at the end of the 10-day window, meeting the 10-day window criterion.

Target chemical and source chemical(s)

Chemical structures of the target chemical and the source chemical are shown in the data matrix, including their physico-chemical properties.

Purity / Impurities

Neryl acetate multi is a multi-constituent. The other component is the E-isomer Geranyl acetate; together these have a purity of > 80%. There is one known impurity, which is << 10% and is similar to Neryl acetate and therefore is considered further.

Analogue approach justification

According to Annex XI 1.5 read across can be used to replace testing when the similarity can be based on a common backbone and a common functional group. When using read across the result derived should be applicable for C&L and/or risk assessment and it should be presented with adequate and reliable documentation, which is presented below.

Analogue selection: For Neryl acetate multi its constituent Geranyl acetate is an isomer of Neryl acetate, and therefore a most similar analogue, for which ready biodegradation information is available.

Structural similarities and differences: Neryl acetate multi consists of Neryl acetate and Geranyl acetate are the same structures and are isomers. Neryl acetate is the Z-isomer (cis) and Geranyl acetate the E-isomer (trans).

Bioavailability: Neryl acetate multi and Geranyl acetate have the same bioavailability because these are the same structures and have the same molecular weights and phyisico-chemical properties.

Biodegradable fragments: Neryl acetate multi and Geranyl acetate have the same structures and therefore the same biodegradable fragments are present, which is supported with BIOWIN 5 and 6 models, which predict probability scores for biodegradation of 0.6342 and 0.6744, respectively, for both constituents.

Uncertainty of the prediction: Differences in cis-trans isomers for biodegradation are not anticipated because Nerol the alcohol-metabolite of the acetate is also ready biodegradable as presented on the ECHA dissemination site for Neryl acetate:https://echa.europa.eu/nl/registration-dossier/-/registered-dossier/21334/5/3/2/?documentUUID=ddd84d24-e308-4208-a7a9-e83424bbf7b0. There are no uncertainties other than those already addressed.

Conclusions on biodegradability for hazard and risk assessment

For Neryl acetate multi no biodegradation information is available. For one of its constituents and isomer, Geranyl acetate, such information is available, which can be used for read-across to fill this data gap. This is because the read-across information is applicable for C&L and/or risk assessment and is documented. Geranyl acetate is readily biodegradable in an OECD TG 301F study. This information can be used for Neryl acetate multi.

Final conclusion: Neryl acetate multi is readily biodegradable.

 

Data matrix supporting the read across toNeryl acetate multi from Geranyl acetate for biodegradation

Common name	Neryl acetate multi	Neryl acetate mono	Geranyl acetate
	Target	Target Major constituent	Source Minor constituent
Chemical name	Multi-constituent	(2Z)-3,7-dimethylocta-2,6-dien-1-yl acetate (cis)	(2E)-3,7-dimethylocta-2,6-dien-1-yl acetate (trans)
Chemical structure
% in product	> 80	55-65	35-45
CAS#	16409-44-2	141-12-8	105-87-3
EC#	240-458-0	205-459-2	203-341-5
Empirical formula	(C12H20O2)	C12H20O2	C12H20O2
Reach registration	2018	Registered	Registered
MW	Not applicable	196	196
Phys-chem*
Appearance	Liquid	Liquid	Liquid
Ws (mg/L)	28.8(exp.)	18.2(est.)	18.2(est.)
log Kow	4.6 (exp.)	4.5(est.)	4.5(est.)
Environmental fate
Biodegradation	Readily biodegradable (Read across)	Readily biodegradable (Read across from Nerol)	Readily biodegradable (OECD TG 301F)

* Physico-chemical properties are calculated with EpiSuite unless stated otherwise i.e. ‘(exp.)’