Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol]and propylidynetrimethanol and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol]

Endpoint summary

Description of key information

No specific studies are available however based on physicochemical data, toxicity data and theoretical assessment, the basic toxicokinetics of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol can be adequately characterised. The substance is likely to be rapidly and extensively absorbed following oral or inhalation exposure, absorption following dermal exposure is likely to be less extensive and more gradual. Rapid and extensive distribution is predicted. Extensive metabolism of the substance is predicted, indicating that excretion is rapid and bioaccumulation is unlikely.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

No specific studies are required. According to Column 1 of Annex VIII of the REACH regulation, assessment of the toxicokinetic behaviour of the substance (to the extent that can be derived from the relevant available information) is required and this is provided. An adequate assessment of the basic toxicokinetics of the substance can be made from the existing toxicity data and theoretical considerations, without the need for specific testing.

Absorption

Based on the relatively low molecular weights, moderate Log Pow values and water solubility, oral absorption is predicted for all components of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol.

No signs of toxicity and no mortality was observed in an acute oral toxicity study performed with the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol at the limit dose of 2000 mg/kg bw (Robertson, 2012). This study does not however provide any useful indication of oral absorption. The results of acute oral toxicity studies performed with the individual components of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol indicate very low toxicity, with mortality or signs of toxicity consistent with systemic absorption observed only at high dose levels. The results of repeated dose oral toxicity studies performed with the components propylidynetrimethanol and 2,2’-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] similarly indicate findings consistent with systemic absorption. Data therefore indicate absorption following oral administration, although the extent of absorption cannot be quantified. A default assumption of 50% oral absorption may be made for the purposes of risk assessment according to REACH Guidance.

The physicochemical properties of the components of Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol favour dermal absorption; the low vapour pressure that the substance or its components coming into contact with the skin will not be significantly lost through volatilisation. Dermal absorption is therefore predicted, but is likely to be less rapid and extensive than oral absorption. In the absence of specific data, a default, conservative dermal absorption value of 50% may be assumed for the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol for the purposes of risk assessment according to REACH guidance and on the basis that dermal absorption will not exceed oral absorption (i.e. the same extent as oral absorption).

Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol is non-volatile; therefore inhalation exposure is not predicted unless the substance is used in situations in which liquid aerosols may be generated (e.g. by spraying). If inhalation exposure were to occur, absorption is potentially extensive. A default assumption of 100% inhalation absorption may be made, if required, for the purposes of risk assessment.

Distribution

Based on water solubility, the systemic distribution of absorbed components of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol and their predicted metabolites is likely to be rapid and extensive following oral, dermal or inhalation exposure.

Metabolism

The OECD QSAR Toolbox liver metabolism simulator predicts a total of eight hepatic metabolites for the component propylidynetrimethanol. Metabolites arise from hydroxylation and/or the sequential oxidation of the hydroxyl groups to the corresponding aldehyde and carboxylic acid.

The OECD QSAR Toolbox liver metabolism simulator predicts a total of 20 hepatic metabolites for the component 2,2’-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol]. Metabolites arise from cleavage of the molecule at the ether linkage to form propylidynetrimethanol. Additional metabolites are predicted to arise from hydroxylation and/or the sequential oxidation of the hydroxyl groups to the corresponding aldehyde and carboxylic acid. A number of the metabolites of 2,2’-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] are common to propylidynetrimethanol.

The OECD QSAR Toolbox liver metabolism simulator predicts a total of 33 hepatic metabolites for the component 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol]. Metabolites arise from cleavage of the molecule at the ether linkages to form Propylidynetrimethanol. Additional metabolites are predicted to arise from hydroxylation and/or the sequential oxidation of the hydroxyl groups to the corresponding aldehyde and carboxylic acids. Formic acid is predicted to arise from the cleavage of both ether groups. A number of the metabolites of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] are also common to 2,2’-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol.

Excretion

The predicted metabolites of the components of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol are of low molecular weight and high water solubility and are therefore likely to be subject to rapid urinary excretion. Based on the likely metabolic pathway and rapid excretion of metabolites, bioaccumulation is not predicted for the components of the Reaction mass of 2,2'-[methylenebis(oxymethylene)]bis[2-ethylpropane-1,3-diol] and 2,2'-[oxybis(methylene)]bis[2-ethylpropane-1,3-diol] and propylidynetrimethanol.