Registration Dossier
Registration Dossier
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EC number: 225-167-9 | CAS number: 4696-57-5
Endpoint summary
Administrative data
Description of key information
The fate of barium dilaurate in the environment can be most accurately evaluated by separate assessment of the fate of the cation barium and the anion dilaurate. Since barium cations and dilaurate anions behave differently in the environment, including processes such as stability, degradation, transport and distribution, a separate assessment of the environmental fate of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.
Barium does not containh ydrolysable groups. Further, biotic degradation is not relevant for inorganic substances such as barium. The coefficient for partitioning of barium between particulate matter and water (Kpsusp) of 5,217 L/Kg was derived for EU waters whereas the Kp for the distribution between sediment and water (Kpsed) was estimated with 3,478 L/kg. For soil, a solid-water partitioning coefficient of 60.3 L/kg was determined experimentally.
Lauric acid: Fatty acids are not persistent in water, and transformation products of environmental concern are also not expected. Available data point to a ready biodegradability of lauric acid under aerobic conditions.
Additional information
The fate of barium dilaurate in the environment is most accurately evaluated by separately assessing the fate of its moieties barium and laurate.
Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of barium dilaurate, a complete dissociation of barium m-toluate resulting in barium cations and dilaurate anions may be assumed under environmental conditions. The respective dissociation is reversible, and the ratio of the salt /dissociated ions is dependent on the metal-ligand dissociation constant of the salt, the composition of the solution and its pH. A metal-ligand complexation constant of barium m-toluate could not be identified. Data for barium appear to be generally limited. However, barium cations tend to form complexes with ionic character as a result of their low electronegativity. Further, the ionic bonding of barium is typically described as resulting from electrostatic attractive forces between opposite charges, which increase with decreasing separation distance between ions. Based on an analysis by Carbonaro et al. (2007) of monodentate binding of bartium to negatively-charged oxygen donor atoms, including carboxylic functional groups, monodentate ligands such as dilaurate anions are not expected to strongly bind to barium. The analysis by Carbonaro & Di Toro (2007) suggests that the following equation models monodentate binding to negatively-charged oxygen donor atoms of carboxylic functional groups:
log KML= αO* log KHL+ βO; where
KML is the metal-ligand formation constant, KHL is the corresponding proton–ligand formation constant, and αO and βO are termed the slope and intercept, respectively. Applying the equation and parameters derived by Carbonaro & Di Toro (2007) and the pKa of lauric acid of 4.95 results in:
log KML= 0.186 * 4.95 – 0.171
log KML= 0.75 (estimated barium-dilaurate formation constant).
Thus, it may reasonably be assumed that based on the estimated barium-dilaurate formation constant, the respective behaviour of the dissociated barium cations and laurate anions in the environment determine the fate of barium dilaurate upon dissolution with regard to (bio)degradation, bioaccumulation and partitioning, resulting in a different relative distribution in environmental compartments (water, air, sediment and soil) and subsequently its ecotoxicological potential.
Thus, in the assessment of enviromental fate of barium dilaurate, read-across to soluble barium substances and lauric acid is applied since the individual ions of barium dilaurate determine its environmental fate. Since barium cations and benzoate anions behave differently in the environment, regarding their fate and toxicity, a separate assessment of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.
In order to evaluate the environmental fate and toxicity of the substance barium dilaurate, information on the assessment entities barium cations and laurate anions were considered. For a documentation and justification of that approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for barium dilaurate.
Reference:
Carbonaro RF & Di Toro DM (2007) Linear free energy relationships for metal–ligand complexation: Monodentate binding to negatively-charged oxygen donor atoms. Geochimica et Cosmochimica Acta 71: 3958–3968.
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