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The Short Chain Alcohol Esters (SCAE C2-C8) category covers esters from a fatty acid (C8-C29) and a C2-C8 alcohol (ethanol, isopropanol, butanol, isobutanol, pentanol, iso-pentanol, hexanol, 2-ethylhexanol or octanol). This category includes both well-defined mono-constituent substances as well as related UVCB substances with varying fatty acid chain lengths.
Fatty acid esters are generally produced by chemical reaction of an alcohol (e.g. isopropanol) with an organic acid (e.g. stearic acid) in the presence of an acid catalyst (Radzi et al., 2005). The esterification reaction is started by a transfer of a proton from the acid catalyst to the alcohol to form an alkyloxonium ion. Acid is protonated on its carbonyl oxygen followed by a nucleophilic addition of a molecule of the alcohol to a carbonyl carbon of acid. An intermediate product is formed. This intermediate product loses a water molecule and proton to give an ester (Liu et al, 2006; Lilja et al., 2005; Gubicza et al., 2000; Zhao, 2000). Esters are the final product of esterification.
In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met”. In particular, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

The rationale for grouping the substances in the SCAE C2-C8 category is based on similarities in physicochemical, ecotoxicological and toxicological properties.
In this particular case, the similarity of the SCAE C2-C8 category members is justified, in accordance with the specifications listed in Regulation (EC) No. 1907/2006 Annex XI, 1.5
Grouping of substances and read across, based on representative molecular structure, physico-chemical properties, tox-, ecotoxicological profiles, supported by a robust set of experimental data and QSAR calculations. There is no convincing evidence that any one of these chemicals might lie out of the overall profile of this category, respectively.
 

Grouping of substances into this category is based on:

• Similar/overlapping structural features or functional groups: All category members are monoesters of alcohols (C2-C8) and fatty acids (C8-C29), with 13 to 32 carbons in total.

• Common precursors and the likelihood of common breakdown products via biological

processes: All category members are subject to enzymatic hydrolysis by pancreatic lipases (Mattson and Volpenhein, 1972; and references therein). The resulting free fatty acids and alcohols are absorbed from the intestine into the blood stream. Fatty acids are either metabolised via the beta-oxidation pathway in order to generate energy for the cell or reconstituted into glyceride esters and stored in the fat depots in the body. The alcohols are metabolised primarily in the liver through a series of oxidative steps, finally yielding carbon dioxide (Berg et al., 2002).

• Similar physico-chemical properties: The log Kow and log Koc values of all category members are high (log Kow > 4, log Koc > 3), increasing with the size of the molecule. The substances are poorly soluble in water and have low vapour pressure. 

• Common properties for environmental fate & eco-toxicology: Based on experimental data, all substances are readily biodegradable, with the exception of Fatty acids, C16-18 and C18 unsatd. branched and linear, butyl esters (CAS No. 163961-32 -8), which is inherently biodegradable, and do not show toxic effects up to the limit of water solubility.

• Common levels and mode of human health related effects: All available experimental data indicate that the members of the SCAE C2-C18 category are not acutely toxic, are not irritating to the skin or to the eyes and do not have sensitizing properties. Repeated dose toxicity was shown to be low for all substances. None of the substances showed mutagenic effects, and toxicity to reproduction was low throughout the category.
 

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006, whereby substances may be considered as a category provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity, the substances listed below are allocated to the category of SCAE C2-C8.
 

Members of the SCAE C2-C8 Category:

EC No.

CAS No.

Chemical name

Alcohol Carbon No.

Fatty acid Carbon No.

Total Carbon

MW

208 -868-4

544-35-4 (b)

Ethyl linoleate

2

18

20

308.50

203-889-5

111-62-6

Ethyl oleate

2

18

20

310.52

293-054-1

91051-05-7

Fatty acids, essential, ethyl esters

2

14 - 22

16 - 24

252.39-368.64

233-560-1

10233-13-3

Isopropyl laurate

3

12

15

242.41

203-751-4

110-27-0

Isopropyl myristate

3

14

17

270.46

205-571-1

142-91-6

Isopropyl palmitate

3

16

19

298.51

203-934-9

112-10-7

Isopropyl stearate

3

18

21

326.56

269-023-3

68171-33-5 (a)

Isopropyl isostearate

3

18

21

326.56

203-935-4

112-11-8

Isopropyl oleate

3

18

21

324.55

292-962-5

91031-58-2

Fatty acids, C16-18, isopropyl esters

3

16 - 18

19 - 21

312.54-326.57

264-119-1

63393-93-1

Fatty acids, lanolin, isopropyl esters

3

10 - 29

13 - 32

214.34-480.85

204-666-5

123-95-5

butyl stearate

4

18

22

340.59

267-028-5

67762-63-4

Fatty acids, tall-oil, butyl esters

4

18

22

423.72

287-039-9

85408-76-0

Fatty acids, C16-18, Bu esters

4

16 - 18

20 - 22

312.53-340.58

284-863-0

84988-74-9

Fatty acids, C16-18 and C18-unsatd., Bu esters

4

16 - 18

20 - 22

312.53- 340.58

 

163961-32-8

Fatty acids, C16-18 and C18 unsatd. branched and linear, butyl esters

4

16 - 18

20 - 22

312.54- 340.58

211-466-1

646-13-9

Isobutyl stearate

4

18

22

340.59

288-668-1

85865-69-6

Fatty acids, C16-18, iso-Bu esters

4

16 - 18

20 - 22

312.54- 340.60

84988-79-4

84988-79-4

Fatty acids, C16-18 and C18-unsatd., iso-Bu esters

4

16 - 18

20 - 22

312.54- 340.60

228-626-1

6309-51-9

Isopenthyl laurate Dodecanoic acid, 2-methyl butyl ester

5

12

17

270.46

694-886-1

1365095-43-7

Isopentyl decanoate and octanoate

5

8 - 10

13 - 15

214.344- 242.40

251-932-1

34316-64-8

Dodecanoic acid, hexyl ester

6

12

18

284.49

218-980-5

2306-88-9

octyl octanoate

8

8

16

256.42

 

84713-06-4

Dodecanoic acid, isooctyl ester

8

12

20

312.53

243-697-9

20292-08-4

2-Ethylhexyl laurate

8

12

20

312.53

692-946-1

649747-80-8

Fatty acids, C8-10, 2-ethylhexyl esters

8

8 - 10

16 - 18

256.42-284.48

603-931-6

135800-37-2

Fatty acids, C8-16, 2-ethylhexyl esters

8

12 - 14

20 - 22

256.42-368.65

249-862-1

29806-73-3

2-ethylhexyl ester palmitate

8

16

24

368.64

 

22047-49-0

2-Ethyl hexyl Stearate

8

18

26

396.69

295-366-3

92044-87-6

Fatty acids, coco, 2-ethylhexyl esters

8

12 - 18

20 - 26

312.53-340.60

292-951-5

91031-48-0

Fatty acids, C16-18, 2-ethylhexyl esters

8

16 - 18

24 - 26

368.65-396.70

285-207-6

85049-37-2

Fatty acids, C16-18 and C18-unsatd., 2-ethylhexyl esters

8

16 - 18

24 - 26

368.65-396.70

247-655-0

26399-02-0

2-Ethylhexyl oleate

8

18

26

394.67

261-819-9

59587-44-9

2-ethylhexyl nonanoate

8

9

17

270.45

297-443-7

93572-14-6

Fatty acids, soya, 2-ethylhexyl esters

8

16 - 18

24 - 26

368.65-396.70

(a) Category members subject to the REACh Phase-in registration deadline of 31 May 2013 are indicated in bold font.
(b) Substances that are either already registered under REACh, or not subject to the REACh Phase-in registration deadline of 31 May 2013, are indicated in normal font.
For all category members registered under REACh a full data set for each endpoint is provided. For substances not subject to the current REACh Phase-in registration, lack of data for a given endpoint is indicated by "--".
 

The available data allow for an accurate hazard and risk assessment of the category and the category concept is applied for the assessment of environmental fate and environmental and human health hazards. Thus, where applicable, environmental and human health effects are predicted from adequate and reliable data for source substance(s) within the group by interpolation to the target substances in the group (read-across approach) applying the group concept in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006. In particular, for each specific endpoint the source substance(s) structurally closest to the target substance is/are chosen for read-across, with due regard to the requirements of adequacy and reliability of the available data. Structural similarities and similarities in properties and/or activities of the source and target substance are the basis of read-across. For a detailed review of the data matrix please refer to the category justification attached in section 13 in IUCLID.

Environmental fate and pathways

Partitioning of substances into the different environmental compartments depends mainly on their physico-chemical properties. Since members of the SCAE C2-C8 category are poorly soluble in water, not volatile, and have high adsorption potential, they are not expected to be found in the air or water compartments. If released in surface waters, the substances would probably partition from the water phase to the sediment. Based on physico-chemical properties, the main target compartments for SCAE C2-C8 category members would thus be soil and sediment. However, the substances are readily biodegradable, with the exception of Fatty acids, C16-18 and C18 unsatd. branched and linear, butyl esters (CAS No. 163961-32-8), which is inherently biodegradable, and highly sorptive, based on calculated estimation, and are thus expected to be eliminated in sewage treatment plants to a high extent. Release to surface waters, and thereby exposure of sediment, is therefore very unlikely. Accumulation into organisms is not expected for members of the SCAE C2-C8 category, since they can be digested by common metabolic pathways, as dietary fats (Berg et al., 2002; Mattson and Volpenheim, 1972; Tocher, 2003).

The fate of the chemicals is also influenced by (bio-)chemical processes they may undergo in the environment. Members of the SCAE C2-C8 category (all substances to be registered and read-across substances used for environmental fate and ecotoxicology) are readily biodegradable and are therefore expected to be rapidly eliminated from the environment. They are not likely to be degraded by abiotic processes. Hydrolysis and photodegradation are not relevant, since the substances are not expected to be present in the water and air compartments. Additionally, estimated hydrolysis rates are very low at environmental conditions.

In conclusion, SCAE C2-C8 category members are expected to be found mainly in the soil compartment, where they are expected to be rapidly degraded by microorganisms.
 

References:

Berg, J.M., Tymoczko, J.L. and Stryer, L., 2002, Biochemistry, 5th edition, W.H. Freeman and Company

Gubicza, L., Kabiri-Badr, A., Keoves, E., Belafi-Bako, K. (2000): Large-scale enzymatic production of natural flavour esters in organic solvent with continuous water removal. Journal of Biotechnology 84(2): 193-196

Lilja, J. et al. (2005). Esterification of propanoic acid with ethanol, 1-propanol and butanol over a heterogeneous fiber catalyst. Chemical Engineering Journal, 115(1-2): 1-12.

Liu, Y. et al. (2006). A comparison of the esterification of acetic acid with methanol using heterogeneous versus homogeneous acid catalysis. Journal of Catalysis 242: 278-286.

Mattson, F.H. and Volpenheim, R.A. (1972): Relative rates of hydrolysis by rat pancreatic lipase of esters of C2-C18 fatty acids with C1-C18 primary n-alcohols, Journal of Lipid Research, 10, 1969

Radzi, S.M. et al.(2005). High performance enzymatic synthesis of oleyl oleate using immobilised lipase from Candida antartica. Electronic Journal of Biotechnology 8: 292-298.

Tocher, D.R. (2003): Metabolism and function of lipids and fatty acids in teleost fish, Reviews of Fisheries Science, 11 (2), 197

Zhao, Z. (2000). Synthesis of butyl propionate using novel aluminophosphate molecular sieve as catalyst. Journal of Molecular Catalysis 154(1-2): 131-135.