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Ecotoxicological information

Sediment toxicity

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Description of key information

According to Annex X of REACH (section 9.5.1. Long-term toxicity to sediment organisms),long-term testing shall be proposed by the registrant if the results of the chemical safety assessment indicates the need to investigate further the effects of the substance and/or relevant degradation products on sediment organisms. The choice of the appropriate test(s) depends on the results of the chemical safety assessment. No reliable data on toxicity of barium in the sediment compartment were identified. Therefore a PNECsediment will be determined using the equilibrium partitioning method based on the PNEC for the aquatic compartment. 

Key value for chemical safety assessment

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).