Indium

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

40.6 µg/L

Assessment factor:

3

Extrapolation method:

sensitivity distribution

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

40.6 µg/L

Assessment factor:

3

Extrapolation method:

sensitivity distribution

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

51.6 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

5 051 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

5 051 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:

7.3 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Under neutral "real-life" water conditions (i.e. between pH 6 -8), Indium trichloride, precipitates and forms In(OH)3 complexes. Therefore no clear dose-response was found between ecotoxicity endpoints and dissolved Indium concentrations. All results were expressed as total recoverable indium concentrations.

Conclusion on classification

General remark

Directly after introduction of Indium metal powder in aqueous test media, only very low In-concentrations (≤1μg/L) are detected. This is explained by the very limited solubility of In metal and the immediate precipitation of Indium ions to In(OH)3.

Indeed, as predicted by chemical equilibrium models and confirmed by TD testing, the higher valence (trivalent) metal In has very low solubility in natural waters and/or ecotoxicity testing media, due to the readily formation of hydroxy complexes In(OH)3. As shown for Aluminium, (which has comparable characteristics in water) such hydroxy complexes may contribute to toxicity (Gensemer et al, 2018), e.g. by polymerisation and/or physical precipitation on the gill surface and as such clogging the gill surface and inhibit its function. As a result, toxicity values for In are expressed as "total recoverable Indium", to include both the In3+ ionic fraction and the In(OH)3 fraction. Consequently, ecotoxicity reference values and PNECs for Indium substances are expressed on a "total recoverable In" basis.

In a general approach to the assessment of In toxicity, information obtained on soluble In-compounds (usually InCl3) is used for determining the ecotoxicity reference value (ERV) for Indium substances. This value refers to the toxicity resulting from the presence of In-ion and In(OH)3 complexes in the "total recoverable" fraction. This value is derived from data on soluble In substances and can thus be considered as conservative for In substances that are sparingly soluble or insoluble, like In metal.

As such, the acute hazard of In metal is based on these general data, obtained on soluble In substances.

The chronic long term aquatic hazard is however based on the comparison of the amount of dissolved metal in solution is compared with a toxicity test performed at the same pH using a soluble metal salt. For this approach there is the need for an ecotox reference value which is compared against dissolved metal concentrations at the end of the T/D study.

Acute (short-term) aquatic hazard

The lowest EC50 observed in the acute aquatic ecotoxicity database covering the 3 main taxonomic groups (unicellular algae, invertebrates, fish) is 1.6 mg In/L on the unicellular algae Pseudokircherniella subcapitata. This EC50 value is related to the concentration of the recoverable total In in solution.

In metal powder is not classified for acute aquatic hazard under CLP.

Chronic (long-term) aquatic hazard

The chronic hazard assessment of In metal is based on the comparison of T/D test results on Indium powder:

The transformation/dissolution testing: measurements of In-release in Transformation/Dissolution (TD) medium at the most conservative pH (6) show very low In-concentration (< 1µg/L) after 28 days (section 4.8). The observed In concentration is far below the chronic ERV of 94 µg/L, derived for soluble In compounds. More specific data on the solubility of the In metal powder show that this very low concentration is primarily due to the very limited solubility of In metal (see results obtained in Ceriodaphnia medium, section 6.1.4.).

As supportive evidence, the chronic ecotoxicity testing on Ceriodaphnia dubia, (which was the most sensitive species identified in the chronic ecotoxicity dataset on soluble In-compounds -see section 6.1.4.) and on the unicellular alga P. subcapitata, which was the most sensitive species in the acute ecotoxicity dataset on InCl3 (see section 6.1.5.)., both show NOECs of 100mg In/L (highest nominal dose tested; very low In concentrations measured in test solutions).

In-metal powder is not chronically toxic and is therefore not classified for chronic aquatic effect under CLP.