2-ethylhexanoic acid, molybdenum salt

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.42 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

1.16 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.042 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

83.37 mg/L

Assessment factor:

1

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

7.41 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.74 mg/kg sediment dw

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:

1.23 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Read-across approach

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of 2-ethylhexanoic acid, molybdenum salt in water, a complete dissociation of 2-ethylhexanoic acid, molybdenum salt resulting in molybdenum and 2-ethylhexanoate ions 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 2-ethylhexanoic acid, molybdenum salt could not be identified. Predictions of stability of another molybdenum carboxylate (Mo isovalerate) in a standard ISO 6341 medium (2 mM CaCl₂, 0.5 mM MgSO₄, 0.77 mM NaHCO₃and 0.077 mM KCl, pH 6 and 8) clearly show that monodentate ligands such as carboxylic acids have no potential for complexing molybdenum ions in solution (<1% of total metal concentration complexed at 0.001 mM Mo) and that molybdenum will be present as the molybdate anion (Visual minteq. Version 3.0, update of 18 October 2012. http://www2.lwr.kth.se/English/OurSoftware/vminteq/index.html).

Thus, in the assessment of environmental toxicity of 2-ethylhexanoic acid, molybdenum salt, read-across to the assessment entities 2-ethylhexanoate and soluble molybdenum substances is applied since the individual released ions of 2-ethylhexanoic acid, molybdenum salt determine its toxicity. Since molybdenum ions and 2-ethylhexanoate ions behave differently in the environment and the relative exposure to both constituent ions is hence predicted to be different from the original composition of 2-ethylhexanoic acid, molybdenum salt, data for the ecotoxicological properties of this substance tested as such is considered less relevant for its effects and risk assessment and a separate assessment is performed for both ions. Please refer to the data as submitted for each individual assessment entity.

Conclusion on classification

The substance 2-ethylhexanoic acid, molybdenum salt will completely dissociate into molybdenum and 2-ethylhexanoate ions after dissolution in water and hence can be regarded as a mixture of both constituent ions. In the absence of toxicity data for 2-ethylhexanoic acid, molybdenum salt itself, its classification for environmental hazards is based on the classification of its moieties (molybdate and 2-ethylhexanoic acid). Both molybdate and 2-ethylhexanoic acid are not classified as hazardous to the aquatic environment, and therefore, it is concluded that 2-ethylhexanoic acid, molybdenum salt is not classified as hazardous to the aquatic environment.

Categories Display