Barium neodecanoate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

769.5 µg/L

Assessment factor:

2

Extrapolation method:

assessment factor

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

64.3 µg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

175.2 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

2 771 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

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:

PNEC soil

PNEC value:

726.2 mg/kg soil dw

Assessment factor:

2

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.022 g/kg food

Assessment factor:

90

Additional information

Read-across approach

There are no ecotoxicological data available for barium neodecanoate and in the assessment of the ecotoxicity of barium neodecanoate, a read-across approach from data for the metal cation and the organic anion is followed. This read-across strategy is based upon the assumption that upon release to the environment and dissolution in aqueous media, barium neodecanoate will dissociate and only be present in its dissociated form, i.e. as barium cation and neodecanoate anion.

Upon dissolution in water, it is indeed predicted that metal carboxylates dissociate completely into the metal cation and the organic anion at environmentally relevant conditions. No information is available on the stability constants of barium neodecanoate, but predictions of stability of other barium carboxylates (Ba propionate, Ba valerate and Ba isovalerate) in a standard ISO 6341 medium (2 mMCaCl₂, 0.5 mM MgSO₄, 0.77 mM NaHCO₃ and 0.077 mM KCl, pH 6 and 8) clearly show that monodentate ligands such as carboxylic acids have no potential for complexing barium ions in solution (< 1% of total metal concentration complexed at 0.001 mM Ba; Visual minteq. Version 3.0, update of 18 October 2012. http://www2.lwr.kth.se/English/OurSoftware/vminteq/index.html).

The fate and behaviour (e.g. partitioning) in the environment for Ba²⁺ and neodecanoate anion are predicted to be significantly different from each other, resulting in a different distribution over the environmental compartments (water, air, sediment and soil). Because the relative exposure to both constituent ions is hence predicted to be different from the original composition of barium neodecanoate, data for the ecotoxicological properties of barium neodecanoate tested as such are considered less relevant for effects and risk assessment and a read-across approach to separate data for both the barium cation and neodecanoate anion is preferred.

For most metal-containing compounds, it is the potentially bioavailable metal ion that is liberated (in greater or lesser amounts) upon contact with water that is the moiety of ecotoxicological concern. The solubility of barium neodecanoate (see IUCLID section 4.8 or chapter 1.3 of the CSR) is above the range of effects concentrations for dissolved barium in the aquatic environment (PNECfreshwater for Ba = 227.8 µg Ba/L). Solubility of Ba-ions in the natural environment is and therefore ecotoxicity data for soluble barium salts can be directly used in a read-across approach for barium neodecanoate. As a conservative approach also the ecotoxicological properties of the carboxylic acid are considered in the effects assessment.

According to the REACH Guidance on information requirements and chemical safety assessment, chapter B.8 Scope of exposure assessment, an environmental exposure and risk assessment is mandatory for a substance if it is classified as hazardous to the aquatic environment or if it has another classification and an aquatic PNEC can be derived. The threshold for PNEC derivation is not reported in the guidance, and was set at the limit test concentration for acute toxicity tests with fish, daphnids and algae, i.e. 100 mg/L. Therefore if a substance is not classified as dangerous for the aquatic environment, but meets the criteria for at least one of the other hazard classes or categories and has L(E)C50 values < 100 mg/L, it was still considered for the environmental exposure assessment.

For barium neodecanoate, only the Ba²⁺ ion is considered for the environmental exposure and risk assessment. Barium is not classified as hazardous to the aquatic environment, but has another official Annex VI classification (Acute Tox. 3 and 4 for barium chloride) and some key L(E)C50 values for effects on aquatic organisms are < 100 mg/L (Table 1). Neodecanoic acid is not classified as hazardous to the aquatic environment and the key L(E)C50 values for the 3 trophic levels of aquatic organisms are > 100 mg/L (Table 1).

Table 1: Acute toxicity data for the constituent ions of barium neodecanoate to aquatic organisms (only most sensitive species per trophic level)

Trophic level	Endpoint	Neodecanoic acid (CAS: 26896-20-8)	Barium ion
Algae	72h ErC50	> 100 mg/L (Desmodesmus subspicatus)	> 34.3 mg Ba/L (Pseudokirchneriella subcapitata)
Fish	96h LC50	> 100 mg/L (Oncorhynchus mykiss)	> 97.5 mg Ba/L (Danio rerio)
Aquatic invertebrates	48h EC50	> 1000 mg/L (Daphnia magna)	14.5 mg Ba/L (Daphnia magna)

Conclusion on classification

The substance barium neodecanoate will dissociate into barium and neodecanoate ions after dissolution in water and hence can be regarded as a mixture of both constituent ions. In the absence of toxicity data for barium neodecanoate itself, its classification for environmental hazards is based on the classification of its moieties (barium and neodecanoic acid). Both barium and neodecanoic acid are not classified as hazardous to the aquatic environment, and according to the summation method, it is therefore concluded that barium neodecanoate is not hazardous to the aquatic environment.