Barium dilaurate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

449.2 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2 343.8 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

811.3 mg/kg soil dw

Assessment factor:

2

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

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 and toxicity 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 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.

Conclusion on classification

The fate and toxicity of barium dilaurate in the environment is most accurately evaluated by separately assessing the fate of its moieties barium and laurate. Barium dilaurate dissolves and dissociates into barium and laurate ions upon contact with an aqueous medium. Therefore, the aquatic hazard potential is assessed based on the toxicity data available for the assessment entities barium and laurate ions since the ions of barium dilaurate determine its environmental fate and toxicity.

Acute (short-term) toxicity data: Aquatic toxicity data of lauric acid point to a low toxic potential to aquatic algae and invertebrates. The ecotoxic potential of the fatty acid chain, i.e. laurate, is assumed to be negligible. Fatty acids are generally not considered to represent a risk to the environment, which is reflected in their exclusion from REACH registration requirements (c.f. REACH Annex V (Regulation (EC) No 987/2008)). EC/LC50 values of 3 trophic levels (algae, invertebrates and fish) range for barium from > 1.15 mg Ba/L to 14.5 mg Ba/L. Thus, all EC50/LC50 values are well above the classification cut-off value for acute (short-term) aquatic hazard category 1 of 1 mg/L. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (a), classification for acute (short-term) aquatic hazard is not required for barium dilaurate.

Chronic (long-term) toxicity: Aquatic acute toxicity data of lauric acid point to a low toxic potential to aquatic algae and invertebrates. Further, 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. Thus, the ecotoxic potential of the fatty acid chain, i.e. laurate, is assumed to be negligible. Fatty acids are generally not considered to represent a risk to the environment, which is reflected in their exclusion from REACH registration requirements (c.f. REACH Annex V (Regulation (EC) No 987/2008)). NOEC/EC10 values of 3 trophic levels (algae, invertebrates and fish) range from ≥ 1.15 mg Ba/L to 2.9 mg Ba/L.In accordance with Regulation (EC) No 1272/2008, classification for chronic aquatic hazard is not required for barium dilaurate as all chronic EC10/NOEC values are above the classification criteria of 1 mg/L. In accordance with Regulation (EC) No 1272/2008, classification for long-term (chronic aquatic) hazard is not required for barium dilaurate. Criteria for the "Safety net" classification in Category Chronic 4 are also not met.

Therefore, Barium dilaurate does not meet classification criteria as acute (short-term) and long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.