Calcium neodecanoate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.528 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.053 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

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:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.018 g/kg food

Assessment factor:

90

Additional information

The fate and toxicity of calcium neodecanoate in the environment is most accurately evaluated by separately assessing the fate of its moieties calcium and neodecanoate.

 

Calcium neodecanoate dissolves and dissociates into calcium and neodecanoate ions upon contact with an aqueous medium. Therefore, the aquatic hazard potential is assessed based on the toxicity data available for calcium and neodecanoate and read-across to the assessment entities soluble calcium substances and neodecanoate is applied since the ions of calcium neodecanoate determine its environmental fate and toxicity.

 

Acute (short-term) toxicity data: As an essential element for living organisms calcium has a very low potential for acute toxicity to freshwater as well as saltwater organisms. Regarding aquatic toxicity data for neodecanoate, data are available from GLP-conform guideline studies for three trophic levels: algae, invertebrates and fish. In sum, reported L(E)C50 values of both calcium and neodecanoate are well above 100 mg/L and corresponding OECD test limits.

 

Chronic (long-term) toxicity: As an essential element for living organisms calcium has a very low potential for long-term toxicity to freshwater as well as saltwater organisms. Regarding aquatic toxicity data for neodecanoate, reliable data are available for invertebrates from a structural analogue (neoheptanoic acid) and QSAR-based estimates for daphnids as well as long-term toxicity data on freshwater fish, also supported by QSAR-based estimates. 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. Thus, chronic aquatic toxicity of calcium neodecanoate to algae, daphnia and fish is not expected below 1 mg/L.

 

Read-across approach

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of calcium neodecanoate in water, a complete dissociation of calcium neodecanoate resulting in calcium 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 calcium neodecanoate could not be identified. Data for alkaline earth metals appear to be generally limited. However, alkaline earth metals tend to form complexes with ionic character as a result of their low electronegativity. Further, the ionic bonding of alkaline earth metals 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 & Di Toro (2007) of monodentate binding of calcium to negatively-charged oxygen donor atoms, including carboxylic functional groups, monodentate ligands such as neodecanoate are not expected to bind strongly with calcium. Accordingly, protons will always out-compete calcium ions for complexation of monodentate ligands given equal activities of free calcium and hydrogen ions. The metal-ligand formation constant (log KML) of calcium withother carboxylic acids, i.e. acetic and benzoic acid, ranging from 0.2 to 0.77 (Bunting & Thong, 1969), further point to a low strength of the monodentate bond between carboxyl groups and calcium.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 Irving–Rossotti slope and intercept, respectively. Applying the equation and parameters derived by Carbonaro & Di Toro (2007) and the pKa of neodecanoic acid of 4.69 results in:

log KML= 0.189 * 4.69 + 0.025

log KML= 0.91 (estimated calcium-neodecanoate formation constant).

Thus, it may reasonably be assumed that based on the estimated calcium-neodecanoate formation constant, the respective behaviour of the dissociated calcium cations and neodecanoate anions in the environment determine the fate of calcium neodecanoate upon dissolution with regard to (bio)degradation, bioaccumulation, 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 toxicity of calcium neodecanoate, read-across to neodecanoate and soluble calcium substances is applied since the individual ions of calcium neodecanoate determine its environmental fate. Since ions and neodecanoate ions 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 of the substance calcium neodecanoate, information on the assessment entities calcium cation and neodecanoate anion 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 calcium neodecanoate.

 

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.

Bunting JW & Thong KM (1969) Stability constants for some 1:1 metal-carboxylate complexes. Canadian Journal of Chemistry, 48, 1654.

Conclusion on classification

Aquatic toxicity studies with calcium neodecanoate are not available, thus aquatic toxicity is addressed with existing data on the dissociation products. Calcium neodecanoate dissolves and dissociates into calcium and neodecanoate ions upon contact with an aqueous medium. Calcium is naturally ubiquitous in the environment and essential for living organisms with a very low potential for toxicity to freshwater and saltwater organisms. Adverse effects are lacking up to and including the respective OECD/EC guidelines limit concentrations. The aquatic hazard assessment is therefore based on the most toxic moiety, i.e. neodecanoic acid, and respective effect concentrations are recalculated for calcium neodecanoate based on the maximum C6-19-branched fatty acid content of 90.6%. Please refer to the section for the respective assessment entity.

 

Acute (short-term) toxicity data:

As an essential element for living organisms, calcium has a very low potential for acute toxicity to freshwater as well as saltwater organisms. Regarding aquatic toxicity data for neodecanoic acid, data are available from GLP-conform guideline studies for three trophic levels: algae, invertebrates and fish. In sum, reported L(E)C50 values of both calcium and neodecanoate are well above 100 mg/L and corresponding OECD test limits. Therefore, calcium neodecanoate does not meet classification criteria as short-term hazard to the aquatic environment under Regulation (EC) No 1272/2008 and its subsequent adaptations.

 

Long-term (chronic) toxicity:

As an essential element for living organisms, calcium has a very low potential for long-term toxicity to freshwater as well as saltwater organisms. Regarding aquatic toxicity data for neodecanoic acid, reliable data are available for invertebrates and fish and QSAR-based estimates 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. Thus, chronic aquatic toxicity of calcium neodecanoate to algae, daphnia and fish is not expected below 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. Based on the surrogate approach (Table 4.1.0 (b) (iii)), calcium neodecanoate would also not meet chronic classification criteria since the EC50 for algae is > 100 mg/L. Therefore, calcium neodecanoate does not meet classification criteria as long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.

In sum, based on read-across of toxicity data available for calcium and neodecanoic acid, calcium neodecanoate does not meet aquatic hazard criteria of Regulation (EC) No 1272/2008.