Fatty acids, C14-18 and C16-18-unsatd., barium salts

Endpoint summary

Additional information

Acute toxicity data

Table below gives an overview of reliable toxicity data that were identified for barium.

Table 1: Overview of reliable acute toxicity data for barium for hazard assessment purposes

Species	Parameter	Endpoint	Value (mg Ba/L)	Reference
Acute fish data
Danio rerio	mortality	96h-LC50	>97.5 12.92 (diss.)	Egeler and Kiefer, 2010
Acute invertebrate data
Daphnia magna	mortality/immobility	48h-LC50	14.5	Biesinger and Christensen, 1972
Algal data
Pseudokirchneriella subcapitata	growth rate	72h-ErC50	>34.3 1.92 (diss.)	Egeler and Kiefer, 2010

Reliable acute data were available for three trophic levels: algae, invertebrates, fish. The lowest effect value (based on total Ba in the test medium) was a 48h-EC₅₀ of 14.5 mg/L.

It should be noted that the outcome of the fish and algal test – when expressed as truly dissolved Ba – resulted in effect levels > 1.92 mg/L (highest measured value), whereas these levels are approximately a factor of 30 higher when expressed as total added Ba (nominal value; to be confirmed by measuring total Ba fraction).

The explanation for these low Ba-levels is most likely related to the formation of BaSO₄:

• The solubility of BaSO₄ is 3 mg/L;
• Concentration of sulfate,e.g., in the algal test medium, is relevant for ambient SO₄-concentrations in EU-surface waters; typical (50P) country-specific values for this anionic compound in EU-surface waters range between 3.20 and 61.6 mg SO₄/L. Taking the 10^th percentile into account, SO₄-levels are situated between 1.97 and 34.3 mg/L.

These data indicate that, when soluble Ba-compounds are brought into the environment or environmental relevant test media, the formation of BaSO₄ is inevitable and is a fundamental fraction of the relevant speciation of Ba in the aqueous environment. Therefore, the potential toxicity of this speciation form or the physiological effects that are association with this physicochemical process (e.g., precipitation onto respiratory organs or on cell wall) should be taken into account.

In that respect, the to Ba-concentrations are more relevant for the evaluation of Ba-toxicity as they include all speciation forms that will be present under natural conditions.

Chronic toxicity data

Since no large dataset from long-term tests for different taxonomic groups is available, no Species Sensitivity Distribution (SSD) can be developed and statistical extrapolation methods can thus not be used to derive the PNECaquatic. Instead, The PNECaquatic calculation will be conducted using assessment factors method. An overview of the chronic data that can be used for PNEC-derivation is given in Table 2 below. All toxicity tests were performed using barium chloride dihydrated as test substance.

Table 2: Overview of most sensitive species-specific LC₅₀/NOEC-values for barium in the freshwater environment

Species	Parameter	Endpoint	Value (mg Ba/L)	Reference
Pseudokirchneriella subcapitata	growth rate	72h-NOEC	>= 34.3	Egeler and Kiefer, 2010
Daphnia magna	mortality	21d-NOEC	2.9	Biesinger and Christensen (1972)

Only one K2 study is available for chronic toxicity to invertebrates (Biesinger and Christensen, 1972) and one K1 study for chronic toxicity to algae (ECT Oekotoxikologie GmbH ,2010). No reliable studies are available for chronic toxicity to fish or higher plants.

One additional reliable endpoint has been identified for the marine organism Cancer anthonyi, for which a nominal 7d-NOEC of 10 mg/L has been reported (endpoint: embryonal hatching).