Cerium vanadium tetraoxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

7.6 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

6.93 µg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

2.5 µg/L

Assessment factor:

10

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

450 µg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

240 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

79 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

7.2 mg/kg soil dw

Assessment factor:

3

Extrapolation method:

sensitivity distribution

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

PNEC oral

PNEC value:

0.167 mg/kg food

Assessment factor:

30

Additional information

Ecotoxicity data are read across from the REACH dossier for vanadium dioxide

A read-across approach is followed based on all information available for inorganic V compounds. This grouping of vanadium compounds for estimating their properties is based on the assumption that properties are likely to be similar or follow a similar pattern as a result of the presence of the common vanadium ion. For most metal-containing compounds, it is indeed the potentially bioavailable metal ion that is liberated (in greater or lesser amounts) upon contact with water that is the moiety of toxicological concern.

This assumption can be considered valid when

i) differences in solubility among V compounds do not affect the results for ecotoxicity of the dissolved vanadium ions,

ii) ecotoxicity is only affected by the vanadium-ion and not by the counter ions, and

iii) there are no important differences in speciation of vanadium in the environment after emissions of the various V compounds.

All reliable data on ecotoxicity vanadium were selected based on soluble V substances or on measured dissolved vanadium concentrations. In assessing the ecotoxicity of metals in the various environmental compartments (aquatic, terrestrial and sediment), it is assumed that toxicity is not controlled by the total concentration of a metal, but by the bioavailable form. No evidence is available on the bioavailable form of vanadium, but for metals, this bioavailable form is generally accepted to be the free metal-ion or oxy-anion in solution. In the absence of speciation data and as a conservative approximation, it can also be assumed that the total soluble vanadium pool is bioavailable. Although vanadium dioxide itself is poorly soluble, the liberated vanadium ion will show the same ecotoxicological properties as observed for soluble vanadium substances.

The reliable ecotoxicity results selected for read-across among vanadium substances are all based on pentavalent V substances (NaVO₃, NH₄VO₃, Na₃VO₄, V₂O₅, Ca₃(VO₄)₂ and ammonium polyvanadate), except for one test on toxicity for birds where VOSO₄ was used. All counter-ions (Na⁺, NH₄⁺, Ca²⁺ and SO₄^2-) are abundantly present in natural environments and are therefore not expected to cause any toxic effect at the concentration ranges tested.

Vanadium can exist in a multitude of different oxidation states from -2 to +5. However, being a first-row transition element, vanadium has the tendency to exist in high oxidation states (+3, +4 and +5), and vanadium ions will form oxy complexes in aqueous solutions (Cotton and Wilkinson, 1988; Crans et al., 1998). The aqueous chemistry of the metal is complex and involves a wide range of oxygenated species for which stabilities depend mainly on the acidity and oxygen level of receiving waters. Under conditions commonly found in oxic fresh waters (i.e., pH between 5 and 9; redox potential [Eh] between 0.5 and 1 V), the pentavalent forms will be the dominant species in solution (Brookins, 1988; Crans et al., 1998; Takeno, 2005). Tetravalent vanadium also may exist under some specific conditions (e.g. pH<5). It is therefore assumed that upon dissolution of vanadium substances, the environmental conditions control the (redox) speciation of vanadium in water, soil and sediment, regardless of the V compound added.

This is confirmed by redox speciation analysis of dissolved vanadium during transformation/dissolution tests for vanadium metal and 5 vanadium compounds with different oxygenation states (VOSO₄, NaVO₃, V₂O₅, V₂O₃ and FeV) according to OECD guidance document 29 (2009). The tests were conducted at a loading of 1 mg/L over 28 days in standard OECD test media at pH 6 and pH 8 under a set of standard laboratory conditions representative of those in standard OECD aquatic ecotoxicity tests. The redox speciation of dissolved vanadium was measured by separating V(IV) and V(V) species by HPLC and analysis via ICP- MS. Regardless of the original redox state of V in the substance, dissolved V is at both pH 6 and 8 dominantly present as pentavalent V (75-97% of all V), with some traces of V(IV) (Table 1 of endpoint summary IUCLID section 5). Recovery of total dissolved V by the measured V(V) and V(IV) was on average 96% and did not differ significantly among the substances tested.

Based on this information, it was concluded that all conditions stated above are met. Therefore, all toxicity data based on soluble V substances (i.e. maximal bioavailability) without concern on toxicity of the counter-ions are used in a read-across approach and all results are expressed based on elemental vanadium concentrations.

Conclusion on classification

Ecotoxicity data are read across from the REACH dossier for vanadium dioxide, which uses data for soluble pentavalent vanadium substances to fulfil ecotoxicity endpoints, as a worst-case approach. The data have been used to determine acute and chronic environmental reference values (ERVs) that can be used for the assessment of cerium vanadium tetraoxide. The following ERVs are determined based on the read across data:

Acute ERV: 0.693 mg V/L

Chronic ERV: 0.120 mg V/L

Cerium vanadium tetraoxide is expected to be less bioavailable than the soluble pentavalent vanadium substances that the ERV values are based on and this needs to be taken into account in the environmental classification. Transformation / dissolution (TD) data are not available for cerium vanadium tetraoxide. However, the environmental classification justification included in the REACH dossier for vanadium dioxide refers to 28-day TD test results available for that substance. Based on comparison of the TD results with the acute and chronic ERVs, it was determined that vanadium dioxide does not require classification for environmental endpoints as the vanadium concentrations released in the TD test were lower than the acute and chronic ERVs. As cerium vanadium tetraoxide is expected to have similar availability in the environment to vanadium dioxide, it is expected that if TD testing was conducted for this substance then the vanadium concentrations released would be similar to those for vanadium dioxide. Cerium vanadium tetraoxide is therefore not classified for environmental endpoints, in line with vanadium dioxide.