Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Justification for grouping of substances and read-across

The Glycol ester category covers esters of an aliphatic diol (ethylene glycol (EG), propylene glycol (PG) or 1,3-butyleneglycol (1,3-BG)) and one or two carboxylic fatty acid chains. The fatty acid chains comprise carbon chain lengths ranging from C6 to C18, mainly saturated but also mono unsaturated C16 and C18, branched C18 and epoxidized C18. Fatty acid esters are generally produced by chemical reaction of an alcohol (e.g. ethylene glycol) 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 acid to form an alkyloxonium ion. The 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 a proton to give an ester (Liu et al, 2006; Lilja et al., 2005; Gubicza et al., 2000; Zhao, 2000). Di- and/or monoesters are the final products of esterification of an aliphatic diol and fatty acids.

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 for human toxicity, 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).

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 Glycol esters.

 

CAS

EC name

Molecular weight

Carbon number in Acid

Carbon number in dihydroxy alcohol

Total Carbons in Glycol Esters

CAS 111-60-4 (b)

Glycol stearate

MW 328.53

C18

C2

C20

CAS 624-03-3 (a)          

Ethane-1,2-diyl palmitate

MW 538.89

C16

C2

C34

CAS 627-83-8               

Ethylene distearate

MW 563.0

C18

C2

C38

CAS 91031-31-1

Fatty acids, C16-18, esters with ethylene glycol

MW 300.48 - 563.00

C16-18

C2

C18-38

CAS 151661-88-0

Fatty acids, C18 and C18 unsatd. epoxidized, ester with ethylene glycol

MW 328.54 - 622.97

C18

C2

C20-38

CAS 29059-24-3

Myristic acid, monoester with propane-1,2-diol

MW 286.45

C14

C3

C17

CAS 1323-39-3

Stearic acid, monoester with propane-1,2-diol

MW 342.55

C18

C3

C21

CAS 37321-62-3

Dodecanoic acid, ester with 1,2-propanediol

MW 258.40 - 440.71

C12

C3

C15-27

CAS 68958-54-3

1-methyl-1,2-ethanediyl diisooctadecanoate

MW 609.03

C18

C3

C39

CAS 31565-12-5

Octanoic acid ester with 1,2-propanediol, mono- and di-

MW 202.29 - 328.49

C8

C3

C11-19

CAS 85883-73-4

Fatty acids, C6-12, esters with propylene glycol

MW 202.29 - 440.71

C6-12

C3

C9-27

CAS 68583-51-7

Decanoic acid, mixed diesters with octanoic acid and propylene glycol

MW 328.49 - 384.59

C8-10

C3

C19-23

CAS 84988-75-0

Fatty acids, C14-18 and C16-18-unsatd., esters with propylene glycol

MW 286.46 - 609.02

C14-18

C3

C17-39

CAS 853947-59-8

Butylene glycol dicaprylate / dicaprate

MW 342.52 - 398.63

C8-10

C4

C20-24

(a) Category members subject to registration are indicated in bold font.

(b) Substances not subject to registration are indicated in normal font.

 

Grouping of substances into this category is based on:

(1) common functional groups: the substances of the category are characterized by ester bond(s) between an aliphatic diol (ethylene glycol (EG), propylene glycol (PG) or 1,3-butyleneglycol (1,3-BG)) and one or two carboxylic fatty acid chains. The fatty acid chains comprise carbon chain lengths ranging from C6 to C18, mainly saturated but also mono unsaturated C16 and C18, branched C18 and epoxidized C18, are included into the category; and

(2) common precursors and the likelihood of common breakdown products via biological processes, which result in structurally similar chemicals: glycol esters are expected to be initially metabolized via enzymatic hydrolysis in the corresponding free fatty acids and the free glycol alcohols such as ethylene glycol and propylene glycol. The hydrolysis represents the first chemical step in the absorption, distribution, metabolism and excretion (ADME) pathways expected to be similarly followed by all glycol esters. The hydrolysis is catalyzed by classes of enzymes known as carboxylesterases or esterases (Heymann, 1980). Ethylene and propylene glycol are rapidly absorbed from the gastrointestinal tract and subsequently undergo rapid biotransformation in liver and kidney (ATSDR, 1997; ICPS, 2001; WHO, 2002; ATSDR, 2010). Propylene glycol will be further metabolized in liver by alcohol dehydrogenase to lactic acid and pyruvic acid which are endogenous substances naturally occurring in mammals (Miller & Bazzano, 1965, Ritchie, 1927). Ethylene glycol is first metabolised by alcohol dehydrogenase to glycoaldehyde, which is then further oxidized successively to glycolic acid, glyoxylic acid, oxalic acids by mitochondrial aldehyde dehydrogenase and cytosolic aldehyde oxidase (ATSDR, 2010; WHO, 2002). The anabolism of fatty acids occurs in the cytosol, where fatty acids esterified into cellular lipids that are the most important storage form of fatty acids (Stryer, 1994). The catabolism of fatty acids occurs in the cellular organelles, mitochondria and peroxisomes via a completely different set of enzymes. The process is termed ß-oxidation and involves the sequential cleavage of two-carbon units, released as acetyl-CoA through a cyclic series of reaction catalyzed by several distinct enzyme activities rather than a multienzyme complex (Tocher, 2003); and

(3) constant pattern in the changing of the potency of the properties across the category:

(a) Physico-chemical properties: The physico-chemical properties of the category members are similar or follow a regular pattern over the category. The pattern observed depends on the fatty acid chain length and the degree of esterification (mono- or diesters). The molecular weight of the category members ranges from 202.29 to 622.97 g/mol. The physical appearance is related to the chain length of the fatty acid moiety, the degree of saturation and the number of ester bonds. Thus, mono- and diesters of short-chain fatty acids and unsaturated fatty acids (C6-14 and C16:1, C18:1) as well as diesters of branched fatty acids (C18iso) are liquid, while mono- and diesters of long-chain fatty acids are waxy solids. All category members are non-volatile (vapour pressure: ≤ 0.066 Pa). The octanol/water partition coefficient increases with increasing fatty acid chain length and number of ester bonds, ranging from log Kow = 1.78 (C6 PG monoester component) to log Kow >10 (C12 PG diester component). The water solubility decreases accordingly (624.3 mg/L for C6 PG monoester component to >0.01 mg/L for C18 PG diester component); and

(b) Environmental fate and ecotoxicological properties: Considering the low water solubility and the potential for adsorption to organic soil and sediment particles, the main compartment for environmental distribution is expected to be the soil and sediment. Nevertheless, persistency in these compartments is not expected since the members of the Glycol Esters Category are readily biodegradable. Evaporation into air and the transport through the atmospheric compartment is not expected since the category members are not volatile based on the low vapour pressure. All members of the category are readily biodegradable and did not show any effects on aquatic organisms in acute and chronic tests representing the category members up to the limit of water solubility. Moreover, bioaccumulation is assumed to be low based on metabolism data.

(c) Toxicological properties: The toxicological properties show that all category members have a similar toxicokinetic behaviour (hydrolysis of the ester bond before absorption followed by absorption and metabolism of the breakdown products) and that the constant pattern consists in a lack of potency change of properties across the category, explained by the common metabolic fate of glycol esters independently of the fatty acid chain length and degree of glycol substitution. Thus, no category member showed acute oral, dermal or inhalative toxicity, no skin or eye irritation properties, no skin sensitisation, are of low toxicity after repeated oral exposure and are not mutagenic or clastogenic and have shown no indications for reproduction toxicity and have no effect on intrauterine development.

The available data allows 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.

A detailed justification for the grouping of chemicals and read-across is provided in the technical dossier (see IUCLID Section 13).

Skin sensitisation

Data Matrix 

CAS #

Skin sensitisation

111-60-4 (b)

Not sensitising

624-03-3 (a)

RA: CAS 627-83-8

627-83-8

Not sensitising

91031-31-1

RA: CAS 627-83-8

151661-88-0

Not sensitising

29059-24-3

Not sensitising

37321-62-3

Not sensitising

68583-51-7

RA: CAS 29059-24-3

RA: CAS 853947-59-8

RA: CAS 37321-62-3

84988-75-0

RA: CAS 627-83-8

RA: CAS 853947-59-8

RA: CAS 29059-24-3

853947-59-8

Not sensitising

(a) Category members subject to registration are indicated in bold font. Only for these substances a full set of experimental results and/or read-across is given.

(b) Substances not subject to registration are indicated in normal font. Lack of data for a given endpoint is indicated by “--“.

CAS 68583-51-7

No studies are available investigating the skin sensitising properties of Decanoic acid, mixed esters with octanoic acid and propylene glycol (CAS 68583-51-7). In order to fulfil the standard information requirements set out in Annex VII, 8.3, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006 read-across from the structurally related category members Myristic acid, monoester with propane-1,2-diol (CAS 29059-24-3), Butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) and Dodecanoic acid, ester with 1,2-propanediol (CAS 37321-62-3) was conducted.

The skin sensitising potential of the category members was investigated in Guinea pig maximisation tests according to EU method B.6 (Kästner, 1989) and according to OECD guideline 406 under GLP conditions (Mürmann, 1992a, b).

In the study with Myristic acid, monoester with propane-1,2-diol, a preliminary range finding test was conducted to evaluate the suitable concentrations for the main study for the intradermal injection and the patch testing. In the main study, 20 female Pirbright white guinea pigs were induced with a single intradermal injection of the test substance at 0.1% in Paraffin perliquid DAB 8 and an epicutaneous occlusive application of the test substance at 15% on the shoulder region 7 days later. A negative control group of 20 animals was treated with Paraffin perliquid DAB 8 only. Epicutaneous challenge exposure was conducted 20 days after the first induction for 24 h under occlusive conditions at concentrations of 2.5% and 5% of the test substance, respectively. All test and control animals showed no skin reactions after 24 and 48 h with one exception only. In one control animal, a slight redness of the skin after 48 h was apparent. No positive control data was included in the study report for reliability check (Kästner, 1989). In two studies with Butylene glycol dicaprylate / dicaprate and Dodecanoic acid, ester with 1,2-propanediol by Mürmann (1992a, b) following preliminary range finding tests, male and female Dunkin Hartley guinea pigs (20 in test group, 10 in control group) were induced with a single intradermal injection of the test substance at 10% in maize germ oil MEH56 or corn oil, respectively. Epicutaneous occlusive application of the undiluted test substance was performed 7 days later. The negative control groups were treated with maize germ oil MEH56 or corn oil, respectively. Epicutaneous challenge exposures were conducted 20 days after the first induction for 24 h under occlusive conditions. The undiluted test substance was applied on the right flank and evaluation of skin reactions was carried out 24, 48 and 72 h after application. After intradermal injection of Freund´s adjuvans and test substance or vehicle only, all test and control animals showed severe erythema and oedema after 24 h. After challenge, all test and control animals showed no skin reactions after 24, 48 and 72 h. The sensitivity of the test system was reported to be checked at regular intervals; however, the data were not included in the study reports (Mürmann, 1992a, b).

In summary, based on the available data on the skin sensitisation properties of the category members, it is concluded, that there is no evidence of sensitising properties of Decanoic acid, mixed diesters with octanoic acid and propylene glycol.

 

CAS 627-83-8

One study investigating the skin sensitising potential of ethylene distearate (CAS No. 627-83-8) is available.
The study was performed according to a Buehler test protocol similar to OECD guideline 406 in Hartley guinea pigs (Müller, 1984). The solid test material was mixed with a few drops of water and applied at a concentration of 100% for epidermal induction and challenge. The negative control group was treated with the vehicle only. No positive control data was included in the study report for reliability check. At challenge, the neat test substance induced no skin effects in the test and negative control group. No further skin reactions after induction and challenge were observed. In addition, a sensitisation study with guinea pigs with limited details is available (Elder, 1982). Two animals were intradermally induced and challenged with 0.1% glycol distearate in a saline solution and showed no skin reactions (Elder, 1982).

In summary, based on all available data, ethylene distearate is not sensitising.

CAS 84988-75-0

No studies are available investigating the skin sensitising properties of Fatty acids, C14-18 and C16-18-unsatd., esters with propylene glycol. In order to fulfil the standard information requirements set out in Annex VII, 8.3, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006 read-across from the structurally related category members Myristic acid, monoester with propane-1,2-diol (CAS 29059-24-3), Butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) and ethylene distearate (CAS 627-83-8) was conducted. The studies of the category members are already discussed under the CAS number 68583-51-7 and CAS number 627-83-8.

The available studies investigating the sensitisation properties of the category members consistently showed negative results. Thus, there is no evidence for sensitising properties of Fatty acids, C14-18 and C16-18-unsatd., esters with propylene glycol.

 

CAS 624-03-3

No studies are available investigating the skin sensitising properties of ethane-1,2-diyl palmitate. In order to fulfil the standard information requirements set out in Annex VII, 8.3, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006 read-across from the structurally related category member ethylene distearate (CAS 627-83-8) was conducted. The studies of the category member ethylene distearate are already discussed under the respective CAS number.

The available studies investigating the sensitisation properties of ethylene distearate consistently showed negative results. Based on the available data on skin sensitisation properties of the category member, it is concluded, that there is no evidence for sensitising properties of ethane-1,2-diyl palmitate.

Additional data

In addition, the category members Glycol Stearate (CAS 111-60-4) and Fatty acids, C18 and C18 unsatd. epoxidized, ester with ethylene glycol (CAS 151661-88-0) did not show skin sensitisation properties, as well.

 

Conclusion for skin sensitisation properties

In conclusion, no skin sensitisation properties of the category members Ethylene distearate (CAS No. 627-83-8), Myristic acid, monoester with propane-1,2-diol (CAS No. 29059-24-3), C8-C10-1,3-Butandiolester (CAS No. 853947-59-8) and Dodecanoic acid, ester with 1,2-propanediol (CAS 37321-62-3) were apparent in the available in vivo studies. Altogether, the available data were consistently negative and thus there is no evidence for skin sensitisation properties of any category member of the Glycol Ester group.

 

References

Agency for Toxic Substances and Disease Registry (ATSDR) (1997): Toxicological Profile for Propylene Glycol. US Department of Health and Human Services. Atlanta, US.

Agency for Toxic Substances and Disease Registry (ATSDR) (2010): Toxicological Profile for Ethylene Glycol. US Department of Health and Human Services. Atlanta, US.

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.

Heymann, E. (1980): Carboxylesterases and amidases. In: Jakoby, W.B., Bend, J.R. & Caldwell, J., eds., Enzymatic Basis of Detoxication, 2nd Ed., New York: Academic Press, pp. 291-323.Gubicza, L. et al. (2000). Large-scale enzymatic production of natural flavour esters in organic solvent with continuous water removal. Journal of Biotechnology 84(2): 193-196.

International Programme on Chemical Safety (IPCS) (2001): Ethylene Glycol. Poisons Information Monograph. PIM 227.

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.

Miller, O.N., Bazzano, G. (1965): Propanediol metabolism and its relation to lactic acid -metabolism. Annals of the New York Academy of Sciences 119, 957-973.

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.

Ritchie, A.D. (1927): Lactic acid in fish and crustacean muscle. Journal of Experimental Biology 4, 327-332.

Stryer, L. (1994): Biochemie. 2nd revised reprint, Heidelberg; Berlin; Oxford: Spektrum Akad. Verlag.

Tocher, D.R. (2003): Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish. Reviews in Fisheries Science 11(2), 107-184.

WHO (2002): Ethylene Glycol: Human Health Aspects. Concise International Chemical Assessment Document 45.

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


Migrated from Short description of key information:
Skin sensitisation: not sensitising (OECD 406)

Justification for selection of skin sensitisation endpoint:
The selected study is the most adequate and reliable study based on overall quality assessment (refer to the endpoint discussion for further details).

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available
Additional information:

This information is not available.


Justification for selection of respiratory sensitisation endpoint:
Study not required according to Annex VII-X of Regulation (EC) No 1907/2006.

Justification for classification or non-classification

According to Article 13 of Regulation (EC) No. 1907/2006 "General Requirements for Generation of Information on Intrinsic Properties of substances", information on intrinsic properties of substances may be generated by means other than tests e.g. from information from structurally related substances (grouping or read-across), provided that conditions set out in Annex XI are met. Annex XI, "General rules for adaptation of this standard testing regime set out in Annexes VII to X” states that “substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity may be considered as a group, or ‘category’ of substances. This avoids the need to test every substance for every endpoint". Since the group concept is applied to the members of the Glycol Ester Category, data will be generated from representative reference substance(s) within the category to avoid unnecessary animal testing. Additionally, once the group concept is applied, substances will be classified and labeled on this basis.

Therefore, based on the group concept, all available data on sensitisation do not meet the classification criteria according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.