Calcium wolframate

Endpoint summary

Description of key information

Calcium wolframate is a moderately soluble inorganic salt consisting of divalent calcium cations and divalent wolframate oxo-anions and thus liberates calcium cations and wolframate anions upon dissolution.Thus, the fate and toxicity of calcium wolframate in the environment is most accurately evaluated by separately assessing the fate of its moieties calcium cations and wolframate anions.

In guideline tests (OECD 201, 202) with the soluble salt sodium wolframate, the 72-h ErC50 for the inhibition of growth rate of P. subcapitata was reported with 52.9 mg sodium wolframate/L whereas the 48-h EC50 for the immobilisation of Daphnia magna was estimated with > 163 mg sodium wolframate/L. The corresponding 72-h NOErC and ErC10 for the inhibition of growth rate of P. subcapitata were estimated with <10.9 mg sodium wolframate/L (all measured).

Since the wolframate content of sodium and calcium wolframate is comparable and sodium wolframate (742 g/L in water; CRC handbook, 2008) is more soluble than calcium wolframate (6.4 mg/L in water), the effect concentrations are well above the water solubility limit of calcium wolframate.

 

Thus, calcium wolframate is expected to have a low potential for toxicity to aquatic algae and invertebrates.

Conclusions on classification:

Aquatic toxicity data of calcium wolframate are not available. The fate and toxicity of calcium wolframate in the environment is most accurately evaluated by separately assessing the fate of its moieties calcium and wolframate. Calcium wolframate dissolves and dissociates into calcium and wolframate ions upon contact with an aqueous medium (at least to some extent). Therefore, the aquatic hazard potential is assessed based on the toxicity data available for the assessment entities calcium and wolframate ions since the ions of calcium wolframate determine its environmental fate and toxicity.

Acute toxicity: Calcium is naturally ubiquitous in the environment and essential for living organisms with a very low potential for toxicity to freshwater and saltwater organisms. Adverse effects are lacking up to and including the respective OECD/EC guidelines limit concentrations. Reliable acute aquatic toxicity data of wolframate are available from guideline studies for algae and daphnia, and the EC50 values amount to 52.9 mg/L and > 163 mg/L sodium wolframate, respectively and are well above the classification cut-off for acute (short-term) aquatic hazard category 1.

Since the wolframate content of sodium and calcium wolframate is comparable and sodium wolframate (742 g/L in water; CRC handbook, 2008) is more soluble than calcium wolframate (6.4 mg/L in water), the effect concentrations are also above the water solubility limit of calcium wolframate. Therefore, calcium wolframate does not meet classification criteria as short-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.

Long-term toxicity: Calcium is naturally ubiquitous in the environment and essential for living organisms with a very low potential for toxicity to freshwater and saltwater organisms Chronic aquatic toxicity data of wolframate are available from a guideline studies for algae, and the 72-h NOErC and ErC10 values for the inhibition of growth rate of P. subcapitata were estimated with <10.9 mg sodium wolframate/L. Since the corresponding EC50 value is > 50 mg/L, we may assume that the respective EC10 value is > 1 mg/L and above the classification cut-off values for long-term aquatic hazard category 1 -3. Since the wolframate content of sodium and calcium wolframate is comparable and sodium wolframate (742 g/L in water; CRC handbook, 2008) is more soluble than calcium wolframate (6.4 mg/L in water), the effect concentrations are considered a conservative estimate for calcium woframate. Criteria for classification in category 4 are also not met. Therefore, calcium wolframate does not meet classification criteria as long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008.

Thus, calcium wolframate does not meet classification criteria as acute and long-term hazard to the aquatic environment under Regulation (EC) No 1272/2008 and subsequent adaptations.