Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Justification for grouping of substances and read-across

The Sorbitan esters category is a series of analogous esters consisting of D-glucitol and natural fatty acids. The category contains UVCB substances, which exhibit differences in chain length (C8-C18), degree of esterification (mono-, di-, tri- and higher esters) and extent of unsaturation (saturated and mono unsaturated).

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 6.1 and 13) and within the CSR Chapter 7.1.

Ecotoxicological parameters for the terrestrial toxicity of the Sorbitan Esters Category

CAS No.

Soil macroorganisms

Terrestrial arthropods

Terrestrial plants

Soil microorganisms

1338-39-2

 

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

26266-57-9

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

91844-53-0

LC50 (14d) > 1000 mg/L (preliminary result)

Waiving

Waiving

WoE

1338-41-6

 

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

71902-01-7

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

1338-43-8

 

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

8007-43-0

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

26266-58-0

LC50 (14d) > 1000 mg/L

Waiving

Waiving

WoE

26658-19-5

RA: CAS 91844-53-0

RA: CAS 26266-58-0

Waiving

Waiving

WoE

 

In absence of a clear indication of selective toxicity towards a specific group of organisms, terrestrial toxicity of sorbitan esters was tested on the earthworm Eisenia fetida, as recommended by the “Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance” (ECHA, 2012). No studies are available for terrestrial arthropods, terrestrial plants or soil microorganisms. However, since sorbitan esters are mainly poorly soluble in water and have potential to adsorb to solid soil particles, a soil dwelling organisms, such as the earthworm, which is exposed to the complete soil system via both dermal and oral uptake, is the most relevant test organism to evaluate the terrestrial toxicity of these substances.

The study was conducted with the category members Sorbitan, octanoate (2:3) and sorbitan trioleate, and no mortality occurred during the 14 day exposure period with none of the two substances. Sorbitan, octanoate (2:3) is the smallest substance in the category and is expected to be the most bioavailable. Sorbitan trioleate is the largest substance and has the highest adsorption potential based on Koc. With these two test substances, low terrestrial toxicity was demonstrated in both ends of the category, and interpolation of the results is possible for other category members. Therefore, there is no reason to expect effects for other category members.

The earthworm studies show that the toxicity of sorbitan esters to terrestrial organisms is very low. Moreover, all category members are expected to be metabolised by organisms after ingestion, which is probably the main uptake route. Esters are known to hydrolyse into carboxylic acids and alcohols by esterases (Fukami and Yokoi, 2012). Carboxylesterase activity has been noted in a wide variety of tissues in invertebrates as well as in fish (Leinweber, 1987; Soldano et al, 1992; Barron et al., 1999, Wheelock et al., 2008). Therefore, it is expected that under physiological conditions, members of the Sorbitan esters category will hydrolyse to D-glucitol and the respective fatty acids. The hydrolysis of sorbitan fatty acid esters occurs within a maximum of 48h for mono-, di- and tri-ester but decreases with the number of esterified fatty acid so that no hydrolysis of hexa-ester occurs (Croda 1951, Mattson and Nolen 1972, Treon 1967, Wick and Joseph 1953). The resulting fatty acids are either metabolised via the β-oxidation pathway in order to generate energy for the cell or reconstituted into glyceride esters and stored in the fat depots in the body (Berg, 2002). The first step of D-glucitol metabolism involves oxidation by L-iditol dehydrogenase to fructose, which is metabolised by the fructose metabolic pathway (Senti, 1986). D-glucitol is naturally found in several berries and fruits as well as in seaweed and algae (FDA, 1972). Larger sorbitan fatty acid esters that will not be hydrolysed, such as hexaesters, are unlikely to cross biological membranes due to their high molecular weight. Additionally, all members of the Sorbitan esters category are readily biodegradable and are thus expected to be rapidly removed from the terrestrial environment by soil microorganisms.

Furthermore, chronic data for Daphnia magna are available for the poorly soluble substances sorbitan stearate and Sorbitan, (Z)-9-octadecenoate (2:3), and no effects occurred up to the limit of water solubility. In the acute studies with the soluble Sorbitan, octanoate (2:3), EC50 values above 10 mg/L were obtained. Such aquatic data can be used as an indicator for potential effects on soil organisms (ECHA, 2012), and in the case of sorbitan esters effects are not to be expected.

Based on the available information, i.e. very low toxicity to earthworm and to aquatic organisms, rapid metabolism and ready biodegradation, short- and long-term effects on terrestrial organisms are very unlikely. Consequently, no further testing is proposed.

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