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Administrative data

Description of key information

OECD 422, rat: NOAEL = 1000 mg/kg bw/d of the read across substance methyl laurate.

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed

Repeated dose toxicity: inhalation - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: inhalation - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion
Endpoint conclusion:
no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

The short chain fatty acid methyl esters category (SCAE Me) covers fatty acid esters of methanol. The category contains both mono-constituent substances, with fatty acid C-chain lengths ranging from C6 to C18 and UVCB substances, composed of single methyl esters in variable proportions. Fatty acid esters are generally produced by chemical reaction of an alcohol (methanol) with an organic acid (e.g. octanoic 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). Monoesters are the final products of esterification.

SCAE Me esters category members include:

Mono-constituent substances:

* Hexanoic acid, methyl ester (CAS No.): 106-70-7 - (MW 130.19)

* Octanoic acid, methyl ester (CAS No.): 111-11-5 - (MW 158.24)

* Decanoic acid, methyl ester (CAS No.): 110-42-9 - (MW 186.29)

* Dodecanoic acid, methyl ester (CAS No.): 111-82-0 - (MW 214.35)

* Tetradecanoic acid, methyl ester (CAS No.): 124-10-7 - (MW 242.40)

* Hexadecanoic acid, methyl ester (CAS No.): 112-39-0 - (MW 270.46)

* Octadecanoic acid, methyl ester (CAS No.): 112-61-8 - (MW 298.51)

* 9-Octadecenoic acid (Z)-, methyl ester (CAS No.): 112-62-9 - (MW 294.48)

* 9, 12-Octadecadienoic acid (Z, Z)-, methyl ester (CAS No.): 112-63-0 - (MW 294.48)

* Hexadecanoic acid (CAS No.): 57-10-3 - (MW 256.43).

UVCB´s:

* Fatty acids, C6-10, methyl esters (CAS No.): 68937-83-7 - (MW 130.19-186.29)

* Fatty acids, C8-10, methyl esters (CAS No.): 85566-26-3 - (MW 158.24-186.29)

* Fatty acids, C10-16, methyl esters (CAS No.): 67762-40-7 - (MW 186.29-270.46)

* Fatty acids, C12-14 (even numbered), methyl esters (CAS No.): 308065-15-8 - (MW 214.35-242.40)

* Fatty acids, C8-18 and C18-unsatd., methyl ester (CAS No.): 67762-37-2 - (MW 158.24-298.51)

* Fatty acids, C12-18, methyl esters (CAS No.): 68937-84-8 - (MW 214.35-298.51)

* Fatty acids, 12-16 and C18-unsatd., methyl esters (CAS No.): 1234694-02-0 - (MW 214.35-298.51)

* Fatty acids, C16-18, methyl esters (CAS No.): 85586-21-6 - (MW 270.46-298.51)

* Fatty acids, palm-oil, methyl esters (CAS No.): 91051-34-2 - (MW 242.40-298.51)

* Fatty acids, C16-18 and C18-unsatd, methyl esters (CAS No.): 67762-38-3 - (MW -270.46-298.51)

* Fatty acids, C14-18 and C16-18-unsatd., methyl esters (CAS No.): 67762-26-9 - (MW 130.19–290.51)

* Fatty acids, coco, Me esters (CAS No.): 61788-59-8 - (MW 214.35-270.46)

* Fatty acids, tallow, Me esters (CAS No.): 61788-61-2 - (MW 242.40-298.51).

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 environmental fate and ecotoxicity, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structural related substances (grouping or read-across)”.

In this particular case, the similarity of the SCAE Me category members is justified in accordance with the specifications listed in Regulation (EC) No 1907/2006, Annex XI, 1.5. The key points the members of the category members share are:

* Common origin:Fatty acid esters (C6-C18) of methanol

* Common precursors and the likelihood of common breakdown products:Fatty acid methyl esters are hydrolysed to the corresponding alcohol (methanol) and fatty acid by esterases (Fukami and Yokoi, 2012), even though it was shown in-vitro that the hydrolysis rate of methyl oleate was lower when compared with the hydrolysis rate of the triglyceride Glycerol trioleate (Mattson and Volpenhein, 1972). Depending on the route of exposure, esterase-catalysed hydrolysis takes place at different places in the organism: After oral ingestion, esters of methanol and fatty acids will undergo chemical changes already in the gastro-intestinal fluids as a result of enzymatic hydrolysis. In contrast, substances that are absorbed through the pulmonary alveolar membrane or through the skin enter the systemic circulation directly before entering the liver where hydrolysis will basically take place. The first cleavage product, the fatty acid, is stepwise degraded by beta-Oxidation based on enzymatic removal of C2units in the matrix of the mitochondria in most vertebrate tissues. The C2units are cleaved as acyl-CoA, the entry molecule for the citric acid cycle. For the complete catabolism of unsaturated fatty acids such as oleic acid, an additional isomerization reaction step is required (see figure below). The alpha- and omega-oxidation, alternative pathways for oxidation, can be found in the liver and the brain, respectively (CIR, 1987). For the second cleavage product methanol, the metabolism is predominating: Initially, methanol is slowly oxidized in the liver by the enzyme alcohol dehydrogenase (ADH) to formaldehyde, which itself is oxidized very rapidly by the enzyme aldehyde dehydrogenase (ALDH) to formic acid. Finally, formic acid is slowly metabolised to CO2and H2O (ICPS, 2002).

* Consistent trends in physico-chemical properties:Water solubility values of the category members tend to decrease at increasing fatty acid C-chain lengths, ranging from 1330 mg/L (C6) to 0.0003 mg/L for C18, whereas partition coefficient values, as expected, increase at increasing C-chain lengths (ranging from 2.3 for C6 to 8.3 for C18). Adsorption to soil and sediment particles is a relevant property for substances containing C8 fatty acids onwards (log Kow > 3). Only the substance with the shortest fatty acid chain length (C6) is considered to have low adsorption potential (log Kow = 2.3). Vapour pressure decreases at increasing chain lengths (ranging from 496 Pa (C6) to 0.00018 Pa (C18) at 25°C). In view of the values reported for C6, C8 (71.9 Pa) and C10 (4.9 Pa), at least partial volatilization of substances containing these fatty acids can be expected. Due to their structural similarities, all category members show consistent trends and therefore, a regular pattern in their physico-chemical properties. Therefore, in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5, these substances may be considered as a category.

* Consistent trends in environmental fate and ecotoxicological profile:The members of the SCAE Me category are readily biodegradable and show low bioaccumulation potential in biota (due to metabolism). The water solubility of the mono-constituent substances within the category decreases at increasing C-chain lengths with a turning point from water soluble to insoluble observed at C14 (water solubility 0.05 mg/L). For the substances containing C6, C8, C10 and C12 fatty acids, water solubilities of 1330 mg/L, 64.4 mg/L, 10.6 mg/L and 7.76 mg/L have been reported respectively. Substances containing C-chain lengths > C14 are insoluble in water, including all UVCB substances within the category (water solubilities < 1 mg/L). Nevertheless, regardless the main environmental compartment of concern (water, soil, sediment) the SCAE Me´s will not be persistent in the environment considering their readily biodegradable nature.Regarding the aquatic toxicity profile in the category, no acute toxicity to fish species is observed. On the other hand, the short-term tests conducted with aquatic invertebrates (Daphnia) and algae for the mono-constituent substances show a toxicity trend. The toxicity increases at increasing C-chain length (starting from C8) up to a toxicity peak at C12 (for which L(E)C50s and NOECs < 1 mg/L have been reported). With decreasing water solubility at longer C-chain lengths (C14), no toxicity up to the highest attainable concentration is observed in Daphnia and algae. For the UVCBs, in those cases where toxicity data are not available, structurally related read-across substances are used in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5: either mono-constituent substances (considering the predominant fatty acid chain lengths in the UVCB) or other analogue UVCBs.

Due to the structural similarities and consistent trend in physico-chemical properties and available data on repeated dose toxicity, the members of the SCAE Me category can be considered as a category of substances, according to Regulation (EC) No. 1907/2006, Annex XI, 1.5.

In addition, read-across from suitable analogue substances was used for the target substance Fatty acids, C16-18, methyl esters as supporting information.

A detailed justification for the grouping of chemicals and read-across is provided in the technical dossier (see IUCLID Section 13) as well as in the Chemical Safety Report (see Part B).

References:

* CIR (1987). Final report on the safety assessment of oleic acid, lauric acid, palmitic acid, myristic acid, stearic acid. J. of the Am. Coll. of Toxicol.6 (3): 321-401.

* Fukami, T. and Yokoi, T. (2012). The Emerging Role of Human Esterases. Drug Metabolism and Pharmacokinetics, Advance publication July 17th, 2012.

* 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, ICPS (2002). Poisons Information Monograph 335, Methanol. http://www.inchem.org/documents/pims/chemical/pim335.htm

* 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 Volpenhein, R.A. (1972). Hydrolysis of fully esterified alcohols containing from one to eight hydroxyl groups by the lipolytic enzymes of the rat pancreatic juice. Journal of lipid research 13: 325-328

* 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

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

Repeated dose toxicity, oral

CAS No.

NOAEL [mg/kg bw/day]

111-82-0

1000 (m,f)

111-62-6 (analogue substance)

5500 (m,f)

123-95-5 (analogue substance)

6000 (m,f)

 

Since no studies investigating the toxicity to reproduction of fatty acids, C16-18, methyl esters (CAS 85586-21-6) are available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to the structurally related category member methyl laurate (CAS 111-82-0) and the analogue substancesethyl oleate (CAS 111-62-6) and butyl stearate (CAS 123-95-5) was conducted.

 

CAS 111-82-0

The read across substance methyl laurate (CAS 111-82-0) was tested for oral toxicity in rats in an OECD 422 combined repeated dose and reproductive toxicity screening test under GLP conditions (MHLW 2000). 12 male and female Crj:CD (SD) rats per dose were administered doses of 0, 250, 500 and 1000 mg/kg/day by gavage. The animals were mated. The test material was administered to females from 14 days before mating until day 3 of lactation and to males for 45 days. Terminal kill was on day 45 for males and on day 4 of lactation for females. The test substance showed no general toxicological effects in either sex. There were no clinical observations attributable to the administration of test substance and there was no mortality in any of the groups. No effects were observed in terms of body weights, food consumption, hematology, blood chemistry, organ weight, necropsy or histopathological findings. Therefore, under the experimental conditions of the study the NO(A)EL for methyl laurate for repeated dose toxicity after oral administration is 1000 mg/kg bw/day in both sexes.

 

CAS 111-62-6 (analogue substance)

Ethyl ester - Repeated dose toxicity:

oral 90 -day NOAEL for rats: 5500 mg/kg bw/day

 

A 90-day oral feeding study (Bookstaff, 2004) was performed with the analogue substance ethyl oleate (CAS 111-62-6) according to the 1993 FDA draft "Redbook II" guidelines (Toxicological Principles for the Safety Assessment of Direct Food Additives and Color Additives Used in Food). The study was performed equivalent to OECD Guideline 408. The purpose of the study was to determine the safety of ethyl oleate (EO) in a 91-day feeding study in Sprague-Dawley rats. EO was mixed into AIN-93G purified diet at levels of 0, 3.3, 6.7, and 10% by weight (approx. 0, 1900, 3800 and 6000 mg/kg bw/day). All diets were calorie- and fat-matched using high oleic safflower oil (HOSO) as the control fat. There were 20 male and 20 female rats per group. EO in the diet was well tolerated and there were no toxicologically significant findings in any of the measured parameters (clinical observations, body weight gains, appearance of the feces, ophthalmic examinations, haematology, clinical chemistry, urinalysis, organ weights, histopathology, or male and female reproductive assessments). The 90-day oral NOAEL was determined to be 10% ethyl oleate, which refers to approximately 5500 mg/kg bw/day when administered by daily feeding to rats for 91-days.

 

 

CAS 123-95-5(analogue substance)

Butyl ester - Repeated dose toxicity:

2 -year NOAEL for rats: 6000 mg/kg bw/day

 

Furthermore a 2-year feeding study was performed with the analogue substance butyl stearate (CAS 123-95-5) comparable to OECD Guideline 452 (Smith, 1953, summarized by Elder, 1985). Groups of 16 male Sprague-Dawley rats received daily doses of 0, 0.01, 0.05, 0.25, 1.25 and 6.25% in the diet. Based on absence of abnormalities in clinical signs, mortality, body weight, food consumption, haematology, clinical chemistry, gross pathology, organ weights and histopathology the chronic NOAEL was found to be 6000 mg/kg bw/day.

 

 

Based on the smallest molecular weight of fatty acids, C12-14 (even numbered), methyl esters, which is identical to that of methyl laurate, the factor 1.0 for equimolar ratio was used. Therefore the NO(A)EL for fatty acids, C12-14 (even numbered), methyl esters is 1000 mg/kg bw/day.

Smallest MW of fatty acids, C12-14 (even numbered), methyl esters: 214.35

 

Therefore, based on a weight of evidence approach, no classification for repeated dose toxicity for all substances within the fatty acid methyl esters category is required.

 

 

There is no data available on the repeated dose toxicity after dermal application and inhalation of the category members.

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 SCAE Me category, data will be generated from a representative category member to avoid unnecessary animal testing. Additionally, once the group concept is applied, substances will be classified and labelled on this basis.

The available data on repeated dose toxicity of Fatty acids, C16-18, methyl esters is conclusive but not sufficient for classification.