Niobium pentachloride

Endpoint summary

Additional information

Data describing the acute aquatic toxicity of niobium pentachloride to aquatic organisms are available for fish, invertebrates, algae and microorganisms.

In a study conducted according to OECD guideline 203 Zebrafish (Danio rerio) were exposed to niobium pentachloride at nominal concentrations of 0 and 100 mg/L under semi-static conditions (limit test). No mortality could be observed.

An activated sludge respiration inhibition test with niobium pentachloride according to OECD 209 resulted in an EL50 > 1000 mg/L and an NOEL ≥ 1000 mg/L.

In a study in accordance with OECD guideline 202 the 48-h acute toxicity of niobium pentachloride to Daphnia magna was studied under semi-static conditions at nominal concentrations of up to 4500 mg/L. Due to highly variable Nb⁵⁺concentrations in solution, effect concentrations were based on nominal loading rates. The 48-hour EL₅₀ was 1498 mg/L. The 48-h NOELR based on immobilization was 889 mg/L and the LOELR was 1333 mg/L.

The toxicity of niobium pentachloride to cultures of Pseudokirchneriella subcapitata after 72-h (growth inhibition test) was investigated in accordance with OECD Guideline 201 at nominal concentrations of up to 2000 mg/L. Results based on growth rate after 72 h were as follows:

-         EL50 = 533 mg/L;

-         LOELR: ≤ 125 mg/L;

-         NOELR: < 125 mg/L.

Due to methodological constraints in the studies investigating the acute toxicity to daphnia and algae, it was not possible to determine effect levels based on measured test item concentrations. After pH adjustment the measured Nb⁵⁺concentrations were low and showed high variability. Measured concentrations were mostly below the limit of quantification (LOQ) and no concentration-response relationship could be established. In these tests, concentrations of the test sample varied due to precipitation, agglomeration and adsorption reactions. In addition, slight changes in pH had profound impact on the test concentrations. Observed effects may therefore rather predominantly refer to elevated NaCl concentrations, originated from neutralization, than released Nb⁵⁺ions.

Reported effects of NaCl concerning the freshwater alga P. subcapitata as well as the aquatic invertebrate Daphnia magna vary but inhibitory concentrations (IC50; inhibition of fluorescence) of 0.87-2.5 g/L and an EC50 of 0.874 g/L, respectively, have previously been determined. Due to a concentration of approximately 2.92 g/L NaCl present at the highest loading rate of 2000 mg/L test substance in OECD test 201 and 4.68 g/L NaCl present at the highest loading rate of 4500 mg/L in OECD test 202, as well as the sensitivity of P. subcapitata and D.magna to salinity, any hypothetical Nb⁵⁺related effects cannot be distinguished from NaCl induced growth inhibition/immobility in the conducted tests.