Oleic acid, copper salt

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

59.5 µg/L

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

39.7 µg/L

Assessment factor:

1

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

1.76 mg/L

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

664.1 mg/kg sediment dw

Assessment factor:

1

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

5 160.3 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

496.2 mg/kg soil dw

Assessment factor:

1

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of oleic acid, copper salt in water, a complete dissociation of oleic acid, copper salt resulting in copper cations and oleate 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 oleic acid, copper salt could not be identified. According to the Irving-Williams series, stability constants formed by divalent first-row transition metal ions generally increase to a maximum stability of copper (Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II)). However, based on an analysis by Carbonaro et al. (2007) of monodentate binding of copper to negatively-charged oxygen donor atoms, including carboxylic functional groups, monodentate ligands such as oleate anions are not expected to bind strongly with copper, especially when compared to polydentate (chelating) ligands. The metal-ligand formation constants (log KML) of copper with other carboxylic acids, i.e. butyric acid and benzoic acid amount to log KML values of 2.14 and 1.51 -1.92, respectively (Bunting and Thong, 1970; CRC, 1972) and point to a moderately stable complexation.

 

 

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 oleic acid of 4.76 (mean of CRC handbook data) results in:

log KML= 0.430 * 4.76 + 0.213

log KML= 2.26 (estimated copper-oleate formation constant).

 

Thus, in the assessment of environmental toxicity oleic acid, copper salt, read-across to the assessment entities oleate and soluble copper substances is applied since the individual ions of oleic acid, copper salt determine its environmental fate. Since copper ions and oleate ions behave differently in the environment regarding their toxicity, a separate assessment of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity. For a documentation and justification of that approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for oleic acid, copper salt.

 

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.

CRC Handbook of Food Additives, 2nd ed. 1972. Butyric acid-copper formation constant.

Bunting, J. W., & Thong, K. M. (1970). Stability constants for some 1: 1 metal–carboxylate complexes. Canadian Journal of Chemistry, 48(11), 1654-1656.

CRC Handbook of physical-chemical properties and environmental fate for organic chemicals, 2nd edition, vol. 1-4, 2006

Conclusion on classification

Aquatic toxicity data of oleic acid, copper salt are not available. Thus, read-across to the assessment entities soluble copper substances and oleic acid is applied since the ions of oleic acid, copper salt determine its fate and toxicity in the environment. Reliable studies indicate that the moiety of ecotoxicological concern are copper cations. Oleic acid is assumed to have a very low potential for acute and long-term aquatic toxicity. Thus, the aquatic hazard assessment is based on the most toxic moiety, i.e. copper cations, and acute and chronic ecotoxicity reference values of copper are recalculated for oleic acid, copper salt based on a maximum copper content of 13.1 %.

Acute (short-term aquatic) hazard: Based on the lowest identified acute ecotoxicity reference value of 12.1 µg Cu/L for copper ions at pH 6 and a maximum copper content of oleic acid, copper salt of 13.1 %, the acute ecotoxicity reference value recalculated for oleic acid, copper salt amounts to 92.4 µg/L oleic acid, copper salt. Therefore, oleic acid, copper salt salts meets classification criteria of acute (short-term) aquatic hazard Category 1 of Regulation (EC) No 1272/2008 with an acute M-Factor of 10. 

 

Long-term (chronic) aquatic hazard: Based on the lowest identified chronic ecotoxicity reference value of 12 µg Cu/L for copper ions at pH 7 and a maximum copper content of oleic acid, copper salt of 13.1 %, the chronic ERV recalculated for oleic acid, copper salt amounts to 91.6 µg/L oleic acid, copper salt.

The chronic ecotoxicity reference value of 91.6 µg/L is compared to criteria for long-term aquatic hazard classification according to Regulation (EC) 1272/2008, taking into account that copper ions are removed from the water column. Based on available evidence (please refer to the attached detailed reports on environmental hazard classification of copper), more than 70% of dissolved copper is removed within 28 days and transformed into stable sulfide complexes (Cu-S) under most “environmentally relevant” conditions. Remobilisation of Cu into the water-column is not likely. Copper is therefore considered rapidly removeable (i.e. equivalent to “rapid degradation” for organic substances).

 

Based on the chronic ecotoxicity reference value of 91.6 µg/l, oleic acid, copper salt meets classification criteria of long-term aquatic hazard Category 2 in accordance with Table 4.1.0 (b) (ii) of Regulation (EC) No 1272/2008.

 

Thus, oleic acid, copper salt meets classification criteria of acute aquatic hazard Category 1 (M-factor 10) and long-term aquatic hazard Category 2 according to Regulation (EC) No 1272/2008 and subsequent adaptations.