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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Barium fluoride will dissociate in aqueous solution to form barium and fluoride ions. Reliable toxicity data for algae are available for barium and fluoride.

For barium the 72h-ErC50 and 72h-NOEC are 1.15 mg Ba/L (dissolved) was observed for growth rate inhibition of Pseudokirchneriella subcapitata corresponding to 1.47 mg BaF2/L (Egeler and Kiefer 2010). Re-calculation to barium fluoride resulted in an ErC50 >1.47 mg/L and an NOEC of >= 1.47 mg/L. For fluoride the 96 -h EC50 for biomass is 43 mg fluoride/L corresponding to 198 mg BaF2/L.

The release of barium upon dissolution of BaF2 determines the chronic toxicity of BaF2 to primary producers under normal environmental conditions, and the 72h-NOEC of 1.47 mg BaF2/L (dissolved) for growth rate inhibition of Pseudokirchneriella subcapitata is considered in the freshwater CSA.

Key value for chemical safety assessment

Additional information

For barium fluoride no data on the toxicity to aquatic algae are available. As barium fluoride in water rapidly dissociates into barium and fluoride ions, it is these ions that are expected to be present in the environment and which will therefore be assessed. Reliable toxicity data for aquatic algae are available for barium and fluoride ions.

Barium

A GLP-compliant OECD guideline 201 study is available for barium chloride (Egeler and Kiefer, 2010). In this study the aquatic toxicity of barium chloride to algae (Pseudokirchneriella subcapitata) was investigated. The 72 hour EC50 for growth rate was > 1.15 mg Ba/L (dissolved) and the NOEC for growth rate was 1.15 mg/L corresponding to 1.47 mg BaF2/L. Effects on growth rate were not observed up to and including the highest (nominal) test concentration of 30.1 mg Ba/L. The dissolved and total fraction were measured. Dissolved levels were below total levels presumbably due to the formation poorly soluble barium sulfate. At the highest concentration, dissolved and total Ba concentration were 1.14 and 30.1 mg/L, respectively (geometric mean measured concentration). Therefore, based on total Ba-levels in solution, the ErC50 and NOEC are >30.1 and ≥ 30.1 mg Ba/L, respectively. Read-across to barium fluoride results in an ErC50 >38.4 mg/L and a NOEC of ≥ 38.4 mg/L. Further, based on dissolved barium concentrations, ErC50 and NOEC amount to >1.15 and ≥1.15 mg Ba/L corresponding to an ErC50 >1.47 mg BaF2/L and a NOEC of ≥ 1.47 mg BaF2/L, respectively.

Fluoride

In the EU Risk Assessment Report for hydrogen fluoride two studies with freshwater alga are reported (EU-RAR, 2001). Both reported tests were performed with sodium fluoride and the results corrected for the fluoride ion. Although data on test conditions are not available, as the data have been reviewed by the EU, these data are considered to be suitably reliable for environmental risk assessment. The lowest effect-value was observed in Scenedesmus sp. with a 96 -h EC50 for biomass of 43 mg fluoride/L corresponding to 198 mg BaF2/L.