2,2-dimethyl-1,3-propanediyl dioleate

Endpoint summary

Additional information

Justification for grouping of substances and read-across

The polyol esters category comprises of 49 aliphatic esters of polyfunctional alcohols containing two to six reactive hydroxyl groups and one to six fatty acid chains. The category contains mono constituent, multi-constituent and UVCB substances with fatty acid carbon chain lengths ranging from C5 - C28, which are mainly saturated but also mono unsaturated C16 and C18, polyunsaturated C18, branched C5 and C9, branched C14 – C22 building mono-, di-, tri-, and tetra esters with an alcohol (i.e.polyol).

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 of category members by interpolation to the target substances/member within the category in accordance with Annex XI, Item 1.5, of Regulation (EC) No 1907/2006. In particular, for each specific endpoint the structurally closest category member(s) is/are chosen for read-across, whilst taking regard to the requirements of adequacy and reliability of the available data. A detailed justification for the grouping of chemicals and read-across is provided in the technical dossier (see IUCLID Section 13).

Terrestrial toxicity

As explained above, the polyol esters category does not need to be grouped with respect to their environmental effects. All poylol esters have a similar profile having the same environmental fate properties; low water solubility, low mobility in soil, ready biodegradability, low persistence and low bioaccumulation potential. Additionally all polyol esters do not show toxicological effects up to the water solubility limit. Nevertheless, for an easier overview the category was organized into three groups, which are characterized according to their major alcohol moiety (NPG, TMP or PE).

The following table illustrates the read across approach taken within the NPG ester group of the polyol esters category. For practicality reasons, only the environmental fate parameters of the relevant substances used as part of a read across approach for the NPG esters of the category have been listed in the table below. The complete data matrix of all polyol esters for aquatic toxicity is however detailed within the category justification attached in IUCLID section 13 of this dossier.

Table: Ecotoxicological parameters for the terrestrial toxicity of the NPG esters

ID	CAS	Toxicity to soil macroorganisms except arthropods	Toxicity to terrestrial arthropods	Toxicity to terrestrial plants	Toxicity to soil microorganisms
# 1	68855-18-5 (a)	RA: CAS 42222-50-4	Waiving	Waiving	Weight of Evidence
# 2	31335-74-7	RA: CAS 42222-50-4	Waiving	Waiving	Weight of Evidence
# 5	70693-32-2	RA: CAS 42222-50-4	Waiving	Waiving	Weight of Evidence
# 6	85186-86-3	RA: CAS 42222-50-4	Waiving	Waiving	Weight of Evidence
# 7	85186-95-4	RA 42222-50-4	Waiving	Waiving	Weight of Evidence
# 9	91031-27-5	RA 42222-50-4	Waiving	Waiving	Weight of Evidence
# 10	42222-50-4	NOEC ≥ 1000 mg/kg dw	Waiving	Waiving	Weight of Evidence
# 11	85005-25-0	RA 42222-50-4	Waiving	Waiving	Weight of Evidence

 a) Category membert subject to the REACh Phase-in registration deadline of 31 May 2013 are indicated in bold font

In absence of a clear indication of selective toxicity towards a specific group of organisms, terrestrial toxicity of NPG 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 NPG esters are poorly soluble in water and have potential to adsorb to solid soil particles, a soil dwelling organism, such as the earthworm is the most suitable species. Earthworms are exposed to the complete soil system via both, dermal absorption and oral uptake of particles. Therefore, it is the most relevant test organism to evaluate the terrestrial toxicity of poorly water soluble and adsorptive substances.

A long-term study according to OECD Guideline 222 is available for the NPG ester 2,2-dimethyl-1,3-propanediyl dioleate (CAS No. 42222-50-4). 2,2-dimethyl-1,3-propanediyl dioleate has the highest adsorption potential based on Koc. No effects were observed at the test concentration of 1000 mg/kg dw in this study. And due to the structural similarity, other NPG eseters are not expected to have effects on terrestrial macroorganisms either.

Furthermore, toxicity is unlikely since all NPG esters 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). The result of the pancreatic digestion of the group member 2,3-dimethyl-1,3-propandiolheptanoate (CAS No. 68855-18-5) shows a degradation of the ester of almost 90% within 4 hours (Oßberger, 2012; IUCLID section 7.1.1). 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, NPG esters will hydrolyse to neopentyl glycol and the respective fatty acids. Neopentyl glycol, undergoes conjugation with glucuronic acid and will be excreted in the urine (Gessner, 1960). The free 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). Metabolic pathways in fish are generally similar to those in mammals. Lipids and their constituents, fatty acids, are in particularly a major organic constituent of fish and play a crucial role as source of metabolic energy for growth, reproduction and mobility, including migration (Tocher, 2003).

Additionally, all NPG esters are readily biodegradable and are thus expected to be rapidly removed from the terrestrial environment by soil microorganisms.

Furthermore, in a chronic study on Daphnia magna, available for the NPG ester 2,2 -dimethyl-1,3 -propanediyl dioleate (CAS No. 42222 -50 -4), no long-term effects were observed at the test concentration of 1 mg/L, which is far above the water solubility of the NPG esters.

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