2-(2-(2-ethoxyethoxy)ethoxy)ethanol

Categories

Category name:

E-Series Glycol Ether Heavies

Justifications and discussions

Category definition:

The category is characterised by the presence of three or more ether groups and a single primary hydroxyl group. The scope of substances that fall within it, is defined as follows:
Category members are made by the reaction ethylene oxide with a single aliphatic alcohol (linear or branched and saturated) to produce a molecule with hydroxyl functionality.
Category members are molecules that are polymeric in nature as defined by the ECHA guidance on monomers and polymers, i.e. they contain at least 3 repeating monomer (EO) units but the substance themselves are not polymers because a single molecule of a given molecular weight constitutes more than 50% of the substance.

Category rationale:

This category covers E series glycol ethers that are produced by the reaction of ethylene oxide (EO) with primary alcohols in the range C1-C4 (methanol to butanol) and that contain three or more ethylene oxide oligomeric units, although the number for discrete molecules (mono-and multi-constituent substances) is three to five. Molecules containing higher numbers of EO units do exist, but these are only normally present as impurities or minor components of the higher molecular weight substance streams from production processes. The generic structure is therefore:

CnH2n+1(OCH2CH2)mOH
where n is 1 to 4 and m is ≥3 (typically 3 or 4)

The hypothesis is that members of this category follow similar metabolic pathways, with the main metabolite derived through oxidation of the hydroxyl function to a carboxylate group and that, for systemic end points, the acid metabolite primarily determines the toxicity of the glycol ether rather than the parent glycol ether itself. A key assumption is that the substances all show the same (low) toxicity properties, with the exception of potential for eye irritation, which is mainly influenced by the length of the terminal alkyl chain. The assumption is that the toxicity properties of any substance in the category can be used as a surrogate for the toxicity of any other member of the category (with the exception of eye irritation.) This category follows approach 5 of those described in the read across assessment framework, where it is assumed that the properties vary in a regular pattern so that properties can be predicted (ECHA, 2017).

The full domain of E series glycol ethers and the scope of this category is shown in the diagram below. The table shows substances that are registered as mono-constituent substances or as components of multi-constituent substances:
Methyl Ethyl Propyl Butyl Pentyl Hexyl
Mono
Di
Tri TEGME TEGEE TEGBE
Tetra TetraEGME * TetraEGBE
Penta PentaEGME *
>=Hexa * *
Mono and di's are not part of the category and therefore not shown. Some may be important only as part of a multi-constituent or UVCB substance. Higher molecular weight members (hexa and above) and those shown with a * may be present as impurities or as minor components of UVCB and multi-constituent substances. Where there is no entry, the substance does not exist commercially.