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A detailedjustification for grouping of substances is provided in section 5 of IUCLID.

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)

Experimental result:

LC50 > 1000 mg/kg

Waiving

Waiving

Weight of evidence

2

31335-74-7

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

3

85711-80-4 (b)

--

--

--

--

4

70693-32-2

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

5

Former 85186-86-3

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

6

85186-86-3

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

7

85186-95-4

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

8

91031-85-5

--

--

--

--

9

91031-27-5

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

10

85116-81-0

RA: CAS 42222-50-4

RA: CAS 68855-18-5

Waiving

Waiving

Weight of Evidence

11

42222-50-4

NOEC (56d) ≥ 1000 mg/kg dw

Waiving

Waiving

Weight of Evidence

12

67989-24-6

--

--

--

--

13

85005-25-0

RA: CAS 42222-50-4

RA: CAS 68855-18-5

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

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

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.

All NPG esters are readily biodegradable and are thus expected to be removed from the terrestrial environment within a short period of time. A short-term study according to OECD 207 is therefore conducted with the smallest NPG ester Heptanoic acid, ester with 2,2-dimethyl-1,3-propanediol (CAS No. 68855-18-5) (log Koc < 5). Due to its smaller size and lower adsorption potential, this substance is assumed to represent the worst case for NPG esters in terms of highest bioavailability. The water solubility is negatively correlated with the C-chain of fatty acids (Lide, 2005). It was therefore used as read-across for all NPG esters. However, since the larger NPG esters have higher adsorption potential (log Koc > 5), a long-term study according to OECD 222 is conducted with one of the largest NPG esters 2,2-dimethyl-1,3-propanediyl dioleate (CAS No. 42222-50-4). This substance represents a worst case for the uptake via ingestion of soil particle bound substance and in terms of longest stability in soil. Summarising, NPG esters present in soil pore water will be readily degraded by microorganism, and long-term exposure is not to be expected. The short-term study is therefore considered sufficient in this case. For highly sorptive substances, which are not expected to be found in pore water (log Koc >5) a long-term study is available. However, these substances are readily biodegradable as well, so if they were to be found in pore water, removal via rapid biodegradation would take place. The two test substances thus represent both ends of the group, and the results will be used to cover all other NPG esters by interpolation.

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.