Manganese neodecanoate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

85.3 µg/L

Assessment factor:

5

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

200 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

2.7 µg/L

Assessment factor:

50

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

121.3 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

230.6 mg/kg sediment dw

Assessment factor:

50

Extrapolation method:

assessment factor

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

23.06 mg/kg sediment dw

Assessment factor:

500

Extrapolation method:

assessment factor

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

167.33 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.018 g/kg food

Assessment factor:

90

Additional information

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion.Based on the solubility of manganese neodecanoate in water, a dissociation resulting in manganese 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 manganese neodecanoate could not be identified. According to the Irving-Williams series, stability constants formed by divalent first-row transition metal ions such as manganese are relatively low compared to other transition metals (Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II)).Further, based on an analysis by Carbonaro et al. (2007) of monodentate binding of manganese to negatively-charged oxygen donor atoms, including carboxylic functional groups, monodentate ligands such as fatty acid anions are not expected to bind strongly with manganese.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 neodecanoic acid of 4.69 results in:

log KML = 0.225 * 4.69 + 0.283

log KML = 1.34 (estimated manganese-neodecanoate formation constant).

Thus, it may reasonably be assumed that based on the estimated manganese-neodecanoate formation constant, the respective behaviour of the dissociated manganese cations and neodecanoate anions in the environment determine the fate of manganese 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 manganese neodecanoate, read-across to neodecanoate and soluble manganese substances is applied since the individual ions of manganese neodecanoate determine its environmental fate. Since manganese 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 and toxicity of the substance manganese neodecanoate, information on the assessment entities manganese cations and neodecanoate 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 manganese 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 of manganese neodecanoate are not available. Thus, read-across to the assessment entities soluble manganese substances and neodecanoate is applied since manganese cations and neodecanoate anions determine its fate and toxicity in the environment.

Acute (short-term) toxicity:

EC/LC50 values of 3 trophic levels (algae, invertebrates and fish) for neodecanoate are > 100 mg/L and thus well above the classification cut-off value for acute (short-term) aquatic hazard category 1 of 1 mg/L.

The lowest EC/LC50 values of 3 trophic levels (algae, invertebrates and fish) for soluble managanese substances are also well above 1 mg Mn/L, the classification cut-off value for acute (short-term) aquatic hazard category 1. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (a), classification for acute (short-term) aquatic hazard is not required for manganese neodecanoate.

(Chronic) long-term toxicity:

Regarding the toxicity of neodecanoate, 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.

Reliable chronic aquatic toxicity data of soluble manganese substances are available for algae, crustacea and fish. The lowest respective effect concentration, i.e. the 60-d NOEC of 0.01 mg Mn/L for Macrobrachium rosenbergii (sub(tropical) giant river prawn) derived in the study by Adhikari et al. (2007), is not for a standard invertebrate species and not from a standardised test method and therefore not selected for classification. Thus, the next lowest effect concentration, i.e. the 65-d NOEC of 0.55 mg Mn/L for Salvelinus fontinalis determined in a study equivalent to OECD 210 (Davies et al. 1998), is selected as chronic ecotoxicity reference value.

Based on a maximum manganese content of 15 % of manganese neodecanoate, the recalculation results in a NOEC of 3.7 mg/L manganese neodecanoate that is well above the classification cut-off value for long-term aquatic hazard of 1 mg/L. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (b) (i), manganese neodecanoate does not meet classification criteria of long-term aquatic hazard.

Thus, manganese neodecanoate does not meet classification criteria of acute (short-term) and long-term aquatic hazard according to Regulation (EC) No 1272/2008 and subsequent adaptations.