2-ethylhexanoic acid, iron salt

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.391 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.535 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.039 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

77.94 mg/L

Assessment factor:

1

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

6.92 mg/kg sediment dw

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.692 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:

1.15 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:

Metal carboxylates are substances consisting of a metal cation and a carboxylic acid anion. Based on the solubility of 2-ethylhexanoic acid, iron salt in water, a complete dissociation of 2-ethylhexanoic acid, iron salt resulting in iron 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.

However, iron species are rapidly removed from environmental solutions as insoluble precipitate at oxic conditions and moderate pH whereas 2-ethylhexanoic acid is rather soluble. Thus, iron is relatively immobile under most environmental conditions, mainly due to the very low solubility of iron (III) hydroxide in its various forms (Salminen, 2005). Under environmental relevant conditions, ferric iron (3 +) oxide-hydroxide forms dominate and concentrations of free Fe3+ ions are low. In addition, dissolved oxygen oxidises free Fe2+ ions in near neutral solutions and ferric (3 +) hydroxides precipitate. Dissolved iron precipitates rapidly with the concentrations of soluble iron ions mainly being controlled by pH, redox conditions as well as the abundance of complexing agents.

A metal-ligand complexation constant of 2-ethylhexanoic acid, iron 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)). Therefore, stabilities of monodentate ligand complexes formed with iron are in general expected to be low when directly comparing to other transition metals. Consequently, based on its solubility in water, 2-ethylhexanoic acid, iron salt is expected to dissociate into its moieties Fe cations and 2-ethylhexanoate.

Thus, in the assessment of environmental fate of 2-ethylhexanoic acid, iron salt, read-across to the assessment entities 2-ethylhexanoate and soluble iron substances is applied since the individual ions of 2-ethylhexanoic acid, iron salt determine its environmental fate. Since iron ions and 2-ethylhexanoate 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. For a documentation and justification of that approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for 2-ethylhexanoic acid, iron salt.

 

Salminen, et al. 2005. FOREGS. Geochemical Atlas of Europe, Part 1, Background information, methodology and maps.

Conclusion on classification

Aquatic toxicity studies with 2-ethylhexanoic acid, iron salt are not available. Thus, read-across to the assessment entities soluble iron substances and 2-ethylhexanoic acid is applied since the ions of 2-ethylhexanoic acid, iron salt determine its fate and toxicity in the environment. Iron is naturally ubiquitous in the environment and essential for normal physiological functioning in species of all trophic levels. Since bioavailablility in aqueous environments is considered a limiting factor for optimal growth of aquatic organisms, iron has a very low potential for toxicity to freshwater and saltwater organisms. The aquatic hazard assessment is therefore based on the toxic moiety, i.e. the 2-ethylhexanoate anion. Existing aquatic toxicity data of 2-ethylhexanoic acid are recalculated for 2-ethylhexanoic acid, iron salt based on a maximum 2-ethylhexanoate content of 92%.

 

Acute (short-term) toxicity: Reliable acute aquatic toxicity data are available from guideline studies for algae, daphnia, and fish and the lowest EC/LC50 values are 53.6 mg/L, 92.8 mg/L and > 108.7 mg/L 2-ethylhexanoic acid, iron salt, respectively, and are well above the classification cut-off for acute (short-term) aquatic hazard category 1. Therefore, 2-ethylhexanoic acid, iron salt does not meet classification criteria as short-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.

 

Chronic (long-term) toxicity: Reliable chronic aquatic toxicity data are available from guideline studies for algae and daphnia and the lowest respective EC10/NOEC values are 34.8 mg/L and 19.6 mg/L 2-ethylhexanoic acid, iron salt, respectively, and well above the classification cut-off values for long-term aquatic hazard category 1 -3. Since long-term data are not available for fish, the surrogate approach is applied. Based on classification criteria for substances for which adequate chronic toxicity are not available in Table 4.1.0 (b) (III), Figure 4.1.1 and adequate acute toxicity data of fish with the LC50 value > 108.7 mg/L, 2-ethylhexanoic acid, iron salt does not classify as long-term aquatic hazard category 1-3. Criteria for classification in category 4 are also not met. Therefore, 2-ethylhexanoic acid, iron salt does not meet classification criteria as long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.

Thus, 2-ethylhexanoic acid, iron salt does not meet classification criteria of acute and long-term aquatic hazard ccording to Regulation (EC) No 1272/2008 and subsequent adaptations.