Fatty acids, C9-13-neo-, barium salts

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

359.4 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

62.9 µg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

1 875 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:

649.1 mg/kg soil dw

Assessment factor:

2

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.022 g/kg food

Assessment factor:

90

Additional information

Read-across

 

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of fatty acids, C9 -13 neo, potassium salts in water, a complete dissociation resulting in potassium cations and neodecanoate 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 fatty acids, C9-C13-neo, barium salts could not be identified. Data for barium appear to be generally limited. However, barium 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. (2011) of monodentate binding of barium to negatively-charged oxygen donor atoms, including carboxylic functional groups, monodentate ligands such as fatty acids, C9-C13-neo anions are not expected to bind strongly with 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 mean pKa of fatty acids, C9-C13-neo of 5.05 results in:

log KML= 0.186 * 5.05 - 0.171

log KML= 0.77 (estimated barium-fatty acids, C9-C13-neo formation constant).

 

Thus, it may reasonably be assumed that based on the estimated barium-fatty acids, C9-C13-neo formation constant, the respective behaviour of the dissociated barium cations and fatty acids, C9-C13-neo anions in the environment determine the fate of fatty acids, C9-C13-neo, barium salts 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 environmental fate and toxicity of fatty acids, C9-C13-neo, barium salts, read-across to soluble barium substances and neodecanoic acid (structural analogue of fatty acids, C9-C13-neo) is applied since individual ions of fatty acids, C9-C13-neo, barium salts determine its environmental fate. Since barium cations and fatty acids, C9-C13-neo 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 fatty acids, C9-C13-neo, barium salts information on the assessment entities barium cations andneodecanoic acid (structural analogue of fatty acids, C9-C13-neo) 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 fatty acids, C9-C13-neo, barium salts.

 

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

Aquatic toxicity studies with fatty acids, C9-C13-neo, barium salts are not available, thus, aquatic toxicity is addressed with existing data on the dissociation products. Fatty acids, C9-C13-neo, barium salts dissolves and dissociates into barium cations and fatty acids, C9-13-neo (with neodecanoic acid being its structural analogue), upon contact with an aqueous medium. For the ions reliable studies are available which indicate that the moiety of ecotoloxicological concern are barium anions. This is supported by reliable environmental data for neodecanoic acid as structural analogue point to very low toxic potential to aquatic algae, invertebrates and fish. The aquatic hazard assessment is therefore based on the most toxic moiety, i.e. barium cations, and the respective PNEC is recalculated for fatty acids, C9-C13-neo, barium salts based on a maximum barium content of 32 %. Please refer to the section for the respective assessment entity.

 

Acute (short-term) toxicity data: 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 and are > 100 mg/L for neodecanoic acid (structural analogue of fatty acids, C9-C13-neo). 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 fatty acids, C9-C13-neo, barium salts.

 

Chronic (long-term) toxicity:

NOEC/EC10 values of 3 trophic levels (algae, invertebrates and fish) range from ≥ 1.15 mg Ba/L to 2.9 mg Ba/L. Regarding the aquatic toxicity of neodecanoic acid (structural analogue of fatty acids, C9-C13-neo), reliable data and QSAR-based estimates are available for daphnids and fish. The respective NOEC/EC10 values are > 1 mg/L. Regarding algae, an EC10 or NOEC is not available for neodecanoate. However, based on the fact that the EC50 for growth rate of algae is > 100 mg/L, we may assume that it is unlikely that the EC10/NOEC < 1 mg/L. According to the QSAR-based outcome of the model ECOSAR v.2.0, neodecanoic acid has a very low potential for chronic toxicity to green algae since the chronic value (ChV = 10^([log (LOEC x NOEC)]/2)) of 12.3 mg/L is >> 1 mg/L. Thus, chronic aquatic toxicity of fatty acids, C9 -13 neo, barium salts to algae, daphnia and fish is not expected below 1 mg/L. Based on the surrogate approach (Table 4.1.0 (b) (iii)) of Regulation (EC) No 1272/2008, fatty acids, C9 -13 neo, barium salts would also not meet chronic classification criteria since the EC50 for algae > 100 mg/L. In accordance with Regulation (EC) No 1272/2008, classification for long-term aquatic hazard is not required for fatty acids, C9-C13-neo, barium salts.