Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
no hazard identified

Marine water

Hazard assessment conclusion:
no hazard identified

STP

Hazard assessment conclusion:
no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:
no hazard identified

Sediment (marine water)

Hazard assessment conclusion:
no hazard identified

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

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

In a study conducted according to OECD guideline 203 zebra fish (Danio rerio) were exposed to tantalum pentachloride at nominal concentrations of 0 and 100 mg/L under semi-static conditions (limit test). No mortality could be observed. Due to methodological constraints, effect levels are provided as nominal loading rates.Hence, the 96-h LL50(nominal) is > 100 mg/L.

An activated sludge respiration inhibition test with tantalum 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 tantalum pentachloride to Daphnia magna was studied under semi-static conditions at nominal concentrations of up to 3000 mg/L. The 48-hour EL50 was 3086 mg/L.

The toxicity of tantalum 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. The EL50 based on growth rate after 72 h is > 2000 mg/L.

Please note that in aquatic toxicity tests conducted with tantalum pentachloride it was not possible to determine effect levels based on measured effective test substance concentrations. Addition of TaCl5 to water leads to strong temperature rise and a strong shift in pH value (<1). Thus, pH values had to be adjusted in all tests by the addition of NaOH. After pH adjustment, the measured Ta5+ concentrations were low and showed high variability. Therefore, no concentration-response relationship could be established. Concentrations of the test item varied due to precipitation, agglomeration and adsorption reactions. In addition, slight changes in pH had profound impact on the test item concentrations. Observed effects in daphnia and algae at very high test substance concentrations may therefore rather predominantly refer to elevated sodium chloride (NaCl) concentrations, originated from neutralization, than released Ta5+ ions.

Reported effects of NaCl concerning the freshwater alga P. subcapitata as well as the aquatic invertebrate Daphnia magna vary but inhibitory concentrations of IC50 = 0.87-2.5 g/L (endpoint affected: fluorescence) and EC50 = 0.874 g/L, respectively, have been determined. Due to a NaCl concentrations of approximately 2.92 g/L present at the highest loading rate of 2000 mg/L test substance in OECD test 201, and 2.34 g/L present at the highest loading rate of 3000 mg/L in OECD test 202, as well as the sensitivity of P. subcapitata and D.magna to salinity, any hypothetical Ta5+ related effects cannot be distinguished from NaCl induced growth inhibition/immobility in the conducted tests. However, effects can be rather attributed to NaCl than to the release of Ta5+ ions.

Conclusion on classification

Tantalum pentachloride hydrolyses immediately in contact with water, forming an extremely acid solution. Upon neutralisation the bulk of the dissolved tantalum precipitates and only a few micrograms per litre remain in solution. Generally, no adverse effects attributable to dissolved tantalum could be identified in aquatic toxicity tests, irrespective of the test species and trophic level. Although some immobility in Daphnia and growth inhibition in algae (yet no mortality in fish) was observed, there was no consistent concentration-response relationship; moreover, these adverse effects were indistinguishable from high salinity effects resulting from neutralisation. In conclusion, no adverse effects on aquatic organisms could be attributed to tantalum at maximum water solubility of tantalum pentachloride after neutralisation. Therefore, no hazard to aquatic organisms is identified. Tantalum pentachloride hence does not require classification for environmental hazards