Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters

Endpoint summary

Additional information

There are no data available on the aquatic toxicity of Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) (CAS 91031-45-7). In order to fulfil the standard information requirements set out in Annex VI - IX, in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across from structurally related substances was conducted.

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 physicochemical, toxicological and ecotoxicological properties may be predicted from data for reference substance(s) by interpolation to other substances on the basis of structural similarity, the substances listed below are selected as reference substances and the available endpoint information is used to predict the same endpoints for Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) (CAS 91031-45-7).

Ecotoxicological parameters for the aquatic toxicity of the target substance Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) and the source substances are presented in the following table.

	Target	Source 1	Source 2	Source 3	Source 4	Source 5
CAS	91031-45-7	627-83-8	91031-31-1	68958-54-3	68583-51-7	853947-59-8
Chemical Name	Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO)	Ethylene distearate	Fatty acids, C16-18, esters with ethylene glycol	1-methyl-1,2-ethanediyl diisooctadecanoate	Decanoic acid, mixed diesters with octanoic acid and propylene glycol	Butylene glycol dicaprylate / dicaprate
MW	388.58; 416.63; 626.99; 683.1	563.00	300.48-563.00	609.03	328.49-384.59	342.52-398.63
Fatty acids chain length	C16-18	C18	C16-18	C18	C8-10	C8-10
Type of glycol	Triethylene glycol	Ethylene glycol	Ethylene glycol	1,2-propylene glycol	1,2-propylene glycol	1,3-butylene glycol
Short-term toxicity to fish	RA: CAS 627-83-8 RA: CAS 68958-54-3 RA: CAS 853947-59-8	Experimental result: LC50 (96 h) > 0.3 mg/L	Experimental result: LC50 (96 h) >10000 mg/L	Experimental result: LC50 (96 h) >100 mg/L	Experimental result: LC0 (96 h) >39 mg/L	Experimental result:LC50 (96 h) >14 mg/L
Long-term toxicity to fish	Waiving based on CAS	--	--	--	--	--
Short-term toxicity to aquatic invertebrates	RA: CAS 68583-51-7 RA: CAS 853947-59-8	--	--	--	Experimental result: EC50 (48 h) >2.7 mg/L	Experimental result:EC50 (48 h) >2 mg/L
Long-term toxicity to aquatic invertebrates	RA: CAS 853947-59-8	--	--	--	--	Experimental result:NOEC (21 d) > watersolubility
Toxicity to aquatic algae	RA: CAS 91031-31-1 RA: CAS 853947-59-8 RA: CAS 68583-51-7	--	Experimental result: EC50 (48 h) >100 mg/L	--	Experimental result: NOEC (72 h) >5.3 mg/L	Experimental result:NOEC (72 h) >3 mg/L
Toxicity to microorganisms	RA: CAS 68583-51-7 RA: CAS 853947-59-8	--	--	Experimental result: EC10 (16 h) >10000 mg/L	Experimental result: EC10 >0.99 mg/L	Experimental result:EC10/50 (3 h) >1099 mg/L

Lack of data for a given endpoint is indicated by “--“.

The above mentioned substances are considered to be similar on the basis of the structural similar properties and/or activities. The available endpoint information is used to predict the same endpoints for Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) (CAS 91031-45-7). A detailed justification for the grouping of chemicals and read-across is provided in the technical dossier (see IUCLID Section 13). This justification shows that there is convincing evidence that these chemicals lie in the overall common profile of this analogue approach. The key points, which are relevant for read-across of environmental effects, that the target and source substances share are:

 

Common functional groups: The target and the source substances are characterized by ester bond(s) between an aliphatic diol (triethylene glycol (TG), ethylene glycol (EG), propylene glycol (PG) or 1,3-butyleneglycol (1,3-BG)) and one or two carboxylic fatty acid chains;

 

Similar physico-chemical properties: For the purpose of read-across of eco-toxicity data, the most relevant physico-chemical parameter are physical state (appearance), vapour pressure, octanol/water partition coefficient and water solubility. All substances have in common, an trend of decreasingwater solubility with increasing molecular weight, fatty acid chain length and degree of esterification (<0.05 mg/L), increasing log Kow (1.78 – 16.39), high log Koc (3.18 - 8.80) and low vapour pressure (VP: < 0.0001 Pa).

 

Common properties for environmental fate & eco-toxicological profile of the target or source substances of this analogue approach: 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 target substance and the source substances are readily biodegradable. Evaporation into air and the transport through the atmospheric compartment is not expected since the target substance and the source substances are not volatile based on the low vapor pressure. The source substances, representing the target substance, did not show any effects on aquatic organisms in acute and chronic tests up to the limit of water solubility. Moreover, bioaccumulation is assumed to be low based on metabolism data.

 

Similar metabolic pathways: Fatty acid esters with an aliphatic alcohol are anticipated to be initially metabolised via enzymatic hydrolysis to the corresponding free fatty acids and the free glycol alcohols such as triethylene glycol, ethylene glycol and propylene glycol. Triethylene glycol, ethylene and propylene glycol are rapidly absorbed from the gastrointestinal tract and distributed within the body (ATSDR, 1997; ICPS, 2001; WHO, 2002; ATSDR, 2010). Following hydrolysis, absorption and distribution of the alcohol component, triethylene glycol has been shown to be excreted via the urine to a high extent without further metabolisation (NTIS, 1984). Ethylene and propylene glycol have been shown toundergo rapid biotransformation in liver and kidney and to be converted subsequently to carbon dioxide via different processes (ATSDR, 1997, 2010; IPCS, 2001). Following absorption into the intestinal lumen, fatty acids are re-esterified with glycerol to TAGs and metabolised in the liver in phase I and II metabolism. Fatty acids also undergo a process termed beta-oxidation that involves the sequential cleavage of two-carbon units, released as acetyl-CoA through a cyclic series of reaction catalysed by several distinct enzyme (Lehninger, 1970; Stryer, 1996).

Discussion

Ecotoxicological studies with freshwater species from all three trophic levels (fish, aquatic invertebrates and algae) are available for the structurally similar source substances ethylene distearate (CAS 627-83-8), decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7), butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) and propylene glycol diisostearate (CAS 68958-54-3). The source substances are characterized by a similar alcohol component (ethylene glycol, propylene glycol or 1,3-butylene glycol) mono- or diesterified with fatty acids with chain lengths of C8-10 or C18 (iso), respectively. If the substance is taken up by fish during the process of digestion and absorption in the intestinal tissue, aliphatic esters like the target substance fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) and the source substances are expected to be initially metabolized via enzymatic hydrolysis.

The corresponding free fatty acids (C16 and C18) and triethyleneglycol are the expected metabolites of this enzymatic reaction for the target substance. The alcohol of the target substance is slightly different to the source substances but aquatic toxicity data showed that ethylene glycol, propylene glycol, 1,3-butylene glycol and triethyleneglycol are of low toxicity to aquatic organisms in acute and chronic studies (EPA, 2010; OECD, 2001, 2004a, b). Thus, it is justified to use the read-across substances even if the alcohol component of the target substance is not exactly the same as the source substances since toxicity is unlikely to occur. Moreover, the target substance and the source substances are characterized by a similar profile in relevant physico-chemical properties like log Kow, log Koc and water solubility implying a similar environmental behaviour and distribution.

Four acute toxicity studies to fish according to internationally accepted guidelines are available for the source substances ethylene distearate (CAS 627-83-8), decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7), Butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) and propylene glycol diisostearate (CAS 68958-54-3). No effects were observed up to the limit of water solubility.The read-across substances which smaller fatty acid chain length are expected to exhibit a higher water solubility and thus a higher bioavailability is consequently to be since the hydrocarbon chain lengths of the fatty acid is directly correlated with thewater solubility (Lide, 2005). Therefore, they represent a worst case for the uptake through the water phase.

The same result was obtained in short-term toxicity studies with aquatic invertebrates for the source substances decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) and butylene glycol dicaprylate / dicaprate (CAS 853947-59-8). No toxicity was observed up to the limit of water solubility in the available studies. Based on the results from these studies in combination with an available chronic result with Daphnia magna, there is no convincing evidence that fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) lies out of the overall toxicity profile. Despite the overall low water solubility of the target and source substances (< 0.05 mg/L), the results from decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) and butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) are considered to exhibit a higher bioavailability through the water phase which is the most common route of uptake in standard aquatic tests. The water solubility directly correlates with the hydrocarbon chain lengths of the fatty acid (Lide, 2005). Thus, considering that these source substances have the smallest Fatty acid chain length (C8-10) this read-across can be seen as a worst case and are adequate representative surrogate substances for the chemical safety assessment of Fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO) (CAS 91031-45-7).

 

Three standard guideline studies investigating the toxicity to aquatic algae are available for the source substances decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7), fatty acids, C16-18, esters with ethylene glycol (CAS 91031-31-1) and butylene glycol dicaprylate / dicaprate (CAS 853947-59-8). No toxicity was observed up to the limit of water solubility in the available studies. The available studies cover fatty acid chain lengths from the lower and upper end of the target substance. Thus, the data gap can be confidently predicted by interpolation.

 

One long-term study with Daphnia magna is available for the read-across substance butylene glycol dicaprylate / dicaprate (CAS 853947-59-8) resulting in a NOEC (21 d) > water solubility. This study was used as read-across based on structural similarities. Moreover, it can be concluded that this substance can be seen as a worst case read-across approach based on the smaller fatty acid chain lengths (C8-10 compared to C16-18). The substance substance is expected to exhibit a higher water solubility and thus a higher bioavailability is consequently to be since the hydrocarbon chain lengths of the fatty acid is directly correlated with the water solubility (Lide, 2005).

 

Toxicity to microorganisms was investigated in two studies for the source substances decanoic acid, mixed diesters with octanoic acid and propylene glycol (CAS 68583-51-7) and butylene glycol dicaprylate / dicaprate (CAS 853947-59-8), respectively. The first study with decanoic acid, mixed diesters with octanoic acid and propylene glycol was not considered to be reliable since only one single species (Pseudomonas putida) was tested. Nevertheless, no effects on O2-consumption were observed. The result from the second study with butylene glycol dicaprylate / dicaprate according to an accepted guideline was considered valid. No effects on respiration of activated sludge microorganisms were observed. Based on structural similarities this study was used for read-across. In combination with results from the available biodegradation study it can be concluded that no effects on the STP microorganism community and the subsequent degradation process in sewage treatment plants is anticipated.

 

In conclusion, no effects on aquatic organisms were observed in the available studies for any of the three trophic levels (fish, daphnia, algae) up to the limit of water solubility, neither in the short-term toxicity tests nor in a long-term test with daphnia.

 

The available data from suitable source substances allow for an accurate assessment of the ecotoxicity profile of the target substance fatty acids, C16-18, 1,2-ethanediylbis(oxy-2,1-ethanediyl) esters (3EO). In each case of read-across, the best suited read-across was chosen. Nevertheless, as it can be seen in the data matrix of the analogue justification in IUCLID Section 13, all reliable data support the hazard assessment by showing a consistent pattern of results.

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