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

Endpoint summary

Description of key information

For Neryl acetate multi the following results were derived:

Species	Guideline / Method	Result	Remarks
Fish (C. carpio)	Read-across	96-h LC50: 11 mg/L	Key study, Rel. 2. Value derived from read-across to Linalyl Acetate (CAS# 115-95-7; tested in an OECD TG 203 flow-through study).
Daphnia magna	Read-across	48-h EC50: 14.1 mg/L	Key study, Rel. 2. Value derived from read-across to Geranyl Acetate (CAS# 105 -87 -3; tested in an OECD TG 202 study)
Green algae (D. subspicatus)	Read-across	72-h ErC50: 3.72 mg/L 72 -h ErC10: 1.19 mg/L	Key study, Rel. 2. Values derived from read-across to Geranyl Acetate (CAS# 105 -87 -3; tested in an OECD TG 201 study)
STP microorganisms	Read-across	NOEC: 100 mg/L	Key study, Rel. 2. Value derived from read-across to Geranyl Acetate (CAS# 105 -87 -3; tested in an OECD TG 301F study (toxicity control))

Additional information

The aquatic toxicity is assessed based on read-across from Linalyl Acetate and Geranyl Acetate to Neryl Acetate Multi. The the read-across rationale for all species is presented below.

Aquatic toxicity of Neryl acetate multi based on read across from data available for Geranyl acetate (CAS# 105-87-3) and Linalyl acetate (CAS# 115-95-7).

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 (cis/trans) 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 aquatic toxicity data available. In accordance with Article 13 of REACH, lacking information can be generated by means other than vertebrate animal testing, i.e. applying alternative methods such as in vitro tests, QSARs, grouping and read-across. For assessing the aquatic toxicity of Neryl acetate multi, the analogue approach is selected because for one of the two main constituents, Geranyl acetate, and for the close structural analogue, Linalyl acetate, experimental data is available which can be used for read-across.

Hypothesis: Neryl acetate multi has the same aquatic toxicity as Geranyl acetate or Linalyl acetate.

Available information: The fish toxicity is derived from Linalyl acetate (OECD TG 203, Rel. 1), while Daphnia and algae toxicity is derived from Geranyl acetate (OECD TG 202 and 201, respectively, both Rel. 1). The acute toxicity values are11 mg/L, 14.1 mg/L, and 3.72 mg/L, for fish, daphnids and algae respectively. A long-term ErC10 of 1.19 mg/L has been determined in algae.

Target chemical and source chemical(s)

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

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.

Analogue approach justification

According to Annex XI section 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 the substance Geranyl acetate is selected as an analogue because it is the E-isomer of Neryl acetate and a constituent of the multi-constituent and for this substance experimental Daphnia and algae information is available. Linalyl acetate shares a similar backbone and functional group with the two key constituents and for this substance acute fish toxicity information is available.

Structural similarities and differences: Neryl acetate multi contains Neryl acetate and Geranyl acetate which are each other Z and E-isomers. Linalyl acetate has a similar unsaturated branched alkyl backbone and the same functional acetate ester group. Linalyl acetate has the same molecular weight but a methyl group close to the acetate group and a double bond at a different spot. One other difference is that Linaly acetate has not a conjugated double bond with the ester, which makes the ester bond somewhat less electrophilic.

Bioavailability: The bioavailability is the same for all, based on similar physico-chemical properties e.g. log Kow is around 4.5.

Reactivity and Mode of Action: Neryl acetate multi and its constituent and analogue are all acetic esters, which are activated by the unsaturated bonds in their chemical structure. ECOSAR categorises all as

vinyl/allyl esters but the double bond in Linalyl acetate is one carbon further from the acetate, which could result in a slightly higher LC50 for fish (ECOSAR calculates a factor of 2 difference between Esters and Vinyl/Allyl esters). In view of algae being the most sensitive species, the slightly higher fish toxicity of Linaly acetate does not have an impact on the overall aquatic toxicity.

Conversion of the effect values: Conversion of the effect values to Neryl acetate multi from the constituent and analogue is not needed because these all have the same molecular weights and similar log Kows.

Uncertainty of the prediction: There are no remaining uncertainties other than those already addressed above.

Data matrix

The relevant information on physico-chemical properties and toxicological characteristics are presented in the Data Matrix.

Conclusions on aquatic toxicity

For Neryl acetate multi no aquatic toxicity information is available. Geranyl- and Linalyl acetate information is used for read-across, which is adequately and reliably documented, is used to fill this data gap. For Linalyl acetate acute fish toxicity is 11 mg/l (OECD TG 203) for Geranyl acetate EC50 for Daphnia and algae are 14.1 and 3.72 mg/l, respectively. The EC10 for algae is 1.19 mg/L, respectively. These data can directly be used for read across in absence of differences in molecular weight and log Kow.

Final conclusion: For Neryl acetate multi, the 96-h LC50 in fish is 11 mg/L, the 48-h EC50 in daphnids is 14.1 mg/L, and the 72-h ErC50 and ErC10 values in aquatic algae 3.72 mg/L and 1.19 mg/L, respectively.

 

Data matrix presenting the information relevant for read-across toNeryl acetate multi from Geranyl acetate and the structural analogue Linalyl acetate for aquatic toxicity

Common names	Neryl acetate multi (Z and E-isomer)	Neryl acetate mono (Z-isomer)	Geranyl acetate (E-isomer)	Linalyl acetate
	Target	Target Major constituent	Source Minor constituent	Source
Systematic name	Multi-constituent	(2Z)-3,7-dimethylocta-2,6-dien-1-yl acetate	(2E)-3,7-dimethylocta-2,6-dien-1-yl acetate	1,6-Octadien-3-ol, 3,7-dimethyl-, acetate
Chemical structure
% in product	>80%	55-65	35-40	Not applicable
CAS#	16409-44-2	141-12-8	115-95-7	115-95-7
Empirical formula	(C12H20O2)	C12H20O2	C12H20O2	C12H20O2
EINECS	240-458-0	205-459-2	203-341-5	204-116-4
REACH registration	2018	Registered	Registered	Registered
MW	(196)	196	196	196
Phys-chem
Appearance	Liquid	Liquid	Liquid	Liquid
Vp (Pa)	2.12 (exp.)	6.2 (est.)	6.2 (est.)	17.5 (est.)
Ws (mg/L)	28.8 (exp.)	18.2 (est.)	18.2 (est.)	40.6 (est.)
log Kow	4.6 (exp.)	4.5 (est.)	4.5 (est.)	4.4 (est.)
Aquatic toxicity
Fish       96-h LC50	11 mg/L (Read across)	11 mg/L (Read across)	11 mg/l (Read across)	11 mg/L (OECD TG 203)
Daphnia48-h EC50	14.1 (Read across)	14.1 (Read across)	14.1 mg/L (OECD TG 202)	15 mg/L* (OECD TG 202)
Algae     72-h ErC50                72-h ErC10	3.72 mg/L 1.19 mg/L (Read across)	3.72 mg/L 1.19 mg/L  (Read across)	3.72 mg/L 1.19 mg/L (OECD 201)	62 mg/L* 9.6 mg/L# (OECD TG 201)

* Data taken from the ECHA dissemination website; #NOEC value (not EC10).