Glycerides, C16-18 and C18-unsatd. mono-

Endpoint summary

Additional information

Justification for grouping of substances and read-across

The Glycerides category covers aliphatic (fatty) acid esters of glycerol. The category contains both well-defined and UVCB substances with aliphatic acid carbon chain lengths of C2 (acetate) and C7-C22, which are mostly linear saturated and even numbered. Some of the substances in the category contain unsaturated fatty acids (e.g. oleic acid in 2,3-dihydroxypropyl oleate, CAS 111-03-5 or general fatty acids C16-22 (even) unsaturated in Glycerides, C14-18 and C16-22-unsatd., mono- and di-, CAS 91744-43-7). Some category members contain branched fatty acids. Branching is mostly methyl groups (e.g. isooctadecanoic acid, monoester with glycerol, CAS 66085-00-5 or 1,2,3-propanetriyl triisooctadecanoate, CAS 26942-95-0). In one category member the branching cannot be located precisely (Glycerides, C16-18 and C18-unsatd., branched and linear mono-, di- and tri, ELINCS 460-300-6). Hydroxylated fatty acids are present in three substances (Castor oil, CAS 8001-79-4; castor oil hydrogenated, CAS 8001-78-3 and 2,3-dihydroxypropyl 12-hydroxyoctadecanoate, CAS 6284-43-1). Hydroxylation occurs on C12 of stearic acid in all these substances. Acetylated chains are present in the last part of the category, comprising fatty acids from C8 to C18 (even) and also C18 unsaturated, additionally a C18 acetylated fatty acid is present with the acetic acid located in C12 position (e.g. Glycerides, castor oil mono-, hydrogenated acetates / 12-acetoxy-octadecanoic acid, 2,3-diacetoxy, CAS 736150-63-3). All glycerides build mono-, di- and tri-esters in variable proportions.

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, 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 6.1 and Section 13) and within chapter 7.1 of the CSR.

The Terrestrial toxicity parameters of the Glycerides category are presented in the table below.

CAS	Toxicity to soil macroorganisms except arthropods	Toxicity to terrestrial arthropods	Toxicity to terrestrial plants	Toxicity to soil microorganisms
142-18-7 (a)	Waiving	Waiving	Waiving	Waiving
6284-43-1	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
620-67-7	NOEC ≥ 1000 mg/kg	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
122-32-7	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
555-43-1	RA: CAS 620-67-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91052-47-0 (b)	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91744-09-1	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
85536-07-8	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91052-49-2	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
67701-33-1	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
67784-87-6	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
97358-80-0	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
31566-31-1	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
85251-77-0	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91052-28-7	NOEC ≥ 1000 mg/kg dw	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91052-54-9	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91744-20-6	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
97722-02-6	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
77538-19-3	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
91744-28-4	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
68606-18-8	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
73398-61-5	RA: CAS 620-67-7	Waiving based on CSA	EC50 (21 d) > 61 mg/kg soil dw	Weight of Evidence (WoE
85536-06-7	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
67701-26-2	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
8001-78-3	RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
97593-30-1	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
97593-30-1	RA: CAS 620-67-7 RA: CAS 91052-28-7	Waiving based on CSA	Waiving based on CSA	Weight of Evidence (WoE)
93572-32-8	Exposure based waiving	Exposure based waiving	Exposure based waiving	Exposure based waiving

(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.

(c) Surrogate substances are either chemicals forming part of a related category of structurally similar fatty acid esters or precursors/breakdown products of category members (i.e. alcohol and fatty acid moieties). Available data on these substances are used for assessment of (eco )toxicological properties by read-across on the same basis of structural similarity and/or mechanistic reasoning as described below for the present category.

 

Two studies investigating the toxicity of Glycerides to soil macroorganisms are available for the monoconstituent substance propane-1,2,3-triyl trisheptanoate (CAS 620-67-7, triglyceride, C7 fatty acid) and the UVCB substance Glycerides, C14-18 and C16-18 unsatd, mono-, di- and tri- (CAS 91052-28-7). The Glycerides category members (with the exception of 2,3-dihydroxypropyl laurate (CAS 142-18-7)) show high adsorption potential based on log Koc values >3. Therefore, tests conducted on soil-dwelling organisms that feed on soil particles (such as earthworms or arthropods) are most relevant for the evaluation of terrestrial toxicity of these substances (Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012)). Propane-1,2,3-triyl trisheptanoate (CAS 620-67-7) and Glycerides, C14-18 and C16-18 unsatd, mono-, di- and tri- (CAS 91052-28-7) cover the whole fatty acid C-chain range within the Glycerides category and also different degrees of esterification. Therefore, these two substances are expected to be good representatives of the toxicity of Glycerides to soil macroorganisms. Both tests were performed according to OECD 207, under GLP conditions (Muckle, 2012; Moser, 2012). The test organisms Eisenia fetida was exposed to the respective test substance for 14 days at a concentration of 1000 mg/kg dw (limit tests). No effects on survival or biomass were reported during the exposure period, leading to NOEC values ≥ 1000 mg/kg dw. Based on these results, toxicity to soil macroorganisms is not anticipated within the Glycerides category. Furthermore, literature data evaluating the effects of fatty acid esters, including one of the Glyceride category members (Glycerol tristearate, CAS No. 555-43-1) to soil microorganisms are available. Hita et al. (1996) investigated the degradation of the model molecule tristearin (Glycerol tristearate) in three different soils for 4 weeks. The amount of stearic acid increased in considerable amounts during the experiment showing the hydrolytic activity of lipases breaking the ester bonds. Furthermore, the investigation of ester fractions showed the generation of new alkanoic acids (methyl stearate, ethyl stearate and propyl stearate) which were not determined in the controls. Nevertheless the amounts were no longer present after 4 weeks, which leads to the assumption that degradation by soil microorganisms had occurred. The same was shown by Cecutti et al. (2002) and Banchio and Gramajo (1997) for other fatty acid esters. Effects on soil microorganisms are thus not expected to be of concern for the Glycerides category members.

A rapid and ultimate degradation of the Glycerides category members in all environmental compartments, including soil, can be expected. All substances of the Glycerides category are readily biodegradable. Chronic exposure of terrestrial organisms is thus very unlikely. Due to the metabolization via enzymatic hydrolysis of the Glycerides category members, a relevant uptake and bioaccumulation in biota is not expected. Enzymatic breakdown will initially lead to the free fatty acid and glycerol (and for this substance additionally acetic acid). Glycerides are naturally stored by organisms as long-term energy reserves. Especially in periods in which the energy demand is high (reproduction, migration, etc.), glycerides are mobilized from the storage sites as source of fatty acids. Fatty acid catabolism is the most important energy source in many species, resulting in the release of acetyl CoA and NADH (throughβ-oxidation) and eventually, via the tricarboxylic cycle, the production of metabolic energy in the form of ATP (Tocher, 2003).

Acute and chronic values obtained in tests conducted on fish, invertebrates, algae and microorganisms showed no adverse effects in the range of the water solubility of the substances (or the highest attainable solubility in aqueous medium), with the exception of Glycerides, palm-oil mono-, hydrogenated, acetates (CAS 93572-32-8) and 2,3-dihydroxypropyl laurate (CAS 142-18-7). The substances are classified as environmental hazard Chronic category 3, according to Regulation (EC) No. 1272/2008, and exposure based waiving is performed to cover the terrestrial endpoints (based on RCR < 1). Based on the information gathered from different taxonomic groups, in combination with the ready biodegradability and rapid metabolization of these substances, it can be concluded that toxicity to terrestrial organisms is highly unlikely for the Glycerides category members.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR