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Ecotoxicological information

Endpoint summary

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Description of key information

Additional information

Read across approach:

In the assessment of the environmental fate and behaviour of barium substances, a read-across approach is applied based on all information available for inorganic barium compounds. This is based on the common assumption that after emission of metal compounds into the environment, the moiety of toxicological concern is the potentially bioavailable metal ion (i.e., Ba2+). Thedissolution of barium substances in the environment and corresponding dissolved Ba levels are controlled by the solubility of barite (BaSO4) and witherite (BaCO3), two naturally occurring barium minerals (Ball and Nordstrom 1991; Menzie et al, 2008), and the concentration of dissolved Ba cations in freshwater is rather low. However, in the dissolved state, the divalent barium cation, is the predominant form in soil, sediments and water. The solubility of barium compounds increases as solution pH decreases (US EPA, 1985a). Nevertheless, the speciation of barium in the environment is considered to be rather simple (USEPA 2005):

-         Barium cations are not readily oxidized or reduced

-         Barium cations do not bind strongly to most inorganic ligands or organic matter

 

Barium  in soils  is not  expected  to  be  very mobile  because of the formation  of water-insoluble salts (sulphate and carbonate) and its inability to form soluble complexes with humic and fulvic materials.  Under acid conditions, however, some of the  water-insoluble  barium compounds  may become soluble and move into ground water (US EPA, 1984).

 

In sum, transport, fate, and toxicity of barium in the environment are largely controlled by the solubility of barium minerals. The barium cation is the moiety of toxicological concern, and thus the hazard assessment is based on Ba2+.

 

US EPA (1985a) Health advisory — barium. Washington, DC, US Environmental Protection Agency, Office of Drinking Water.

 

US EPA (1984) Health effects assessment for barium,Cincinnati, Ohio, US Environmental Protection Agency, Office of Health and Environmental

Assessment, Environmental Criteria and Assessment Office (Prepared for the Office of Emergency and Remedial Responsible, Washington, DC) (EPA 540/1-86-021).

 

Acute toxicity data

Table below gives an overview of reliable toxicity data that were identified for barium. It is note that the values given in the table are based on barium concentration.

 

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

Species

Parameter

Endpoint

Value
(mg Ba/L)

Reference

Danio rerio

mortality 

96h-LC50

>97.5

> 3.5(diss .) 

Egeler and Kiefer, 2010 

Daphnia magna

mortality/immobility 

48h-LC50 

14.5 

Biesinger and Christensen, 1972 

Pseudokirchneriella subcapitata 

growth rate 

72h-ErC50 

>30.1

> 1.15(diss.)

Egeler and Kiefer, 2010

 

Reliable acute data were available for three trophic levels: algae, invertebrates, fish. The lowest effect value (based on dissolved barium in the test medium) is a 72h-ErC50of >1.15 mg Ba/L, for growth reduction in algae.

 

It should be noted that the outcome of fish and algae tests, when expressed as dissolved barium concentrations resulted in effect levels of > 3.5 mg Ba/L and > 1.15 mg Ba/L, respectively, whereas these levels are approximately a factor of ~30 higher when expressed as total barium, i.e. > 97.5 mg/L and > 30.1 mg/L of total Ba, respectively.

 

The low recovery of dissolved barium may be explained by the precipitation of barium-sulfates in the test medium. However, the Chemical Safety Assessment is based on dissolved barium concentration.

Chronic toxicity data

Reliable studies on chronic toxicity of barium to the aquatic environment are available for three trophic levels: algae, invertebrates and fish. The toxicity tests were performed using barium dichloride dihydrate as test substance.

 

- In the study of growth inhibition of the algae speciesPseudokirchneriella subcapitataperformedby Egeler and Kiefer (2010) using barium dichloride dihydrate as test substance, all significant effect levels (acute and chronic) were ≥ 30.1 mg total Ba/L and ≥ 1.15 mg dissolved Ba/L. Thus, the 72-h NOEC is ≥ 30.1 mg total Ba/L and 72-h NOEC is ≥ 1.15 mg dissolved Ba/L.

 

-  The study on the chronic toxicity of barium to invertebrates (Biesinger and Christensen, 1972) reported a calculated NOEC forDaphnia magna(i.e., EC16/2) of 2.9 mg Ba/L (nominal).

 

- A chronic fish study according to OECD 210 (Gilberg, 2014) was performed withDanio rerio. The NOEC based on total barium was ≥ 40.3 mg/L, the NOEC for dissolved barium was ≥ 1.26 mg/L.

 

The low recovery of dissolved barium may be explained by the precipitation of barium-sulfates in the test medium.However, the Chemical Safety Assessment is based on dissolved barium concentration.

 

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

Species

Parameter

Endpoint

Value (mg Ba/L)

Reference

Danio rerio

mortality

33d-NOEC 

>= 40.3
>= 1.26(diss).

Gilberg, 2014 

Pseudokirchneriella subcapitata

 

72h-NOECr 

>= 30.1
>= 1.15(diss).

Egeler and Kiefer, 2010 

Daphnia magna

mortality

21d-NOEC

2.9 

Biesinger and Christensen, 1972

 

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).