Indium

Short-term toxicity to aquatic invertebrates

Description of key information

Information obtained on soluble InCl3 is considered relevant for the general ecotoxicity of the In3+ ion, in combination with In(OH)3 complexes. It is therefore also used for the general conservative assessment of the acute ecotoxicity of In metal (powder). Given the proven very limited solubility and lack of aquatic ecotoxicity of In metal powder (see results on chronic testing with C. dubia and P. subcapitata), this general approach must be considered as very conservative for In metal.

There were studies on 3 freshwater species and 3 saltwater species available.

In freshwater, EC50 varied between >3.1 mg In/L (Hyalella azteca) and >455.5 mg/L (Daphnia magna)

in marine water, EC50 varied between 24.4 mg In/L (Brachionus plicatilis) and 51.0 mg In/L (Artemia salina)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

455 500 µg/L

Marine water invertebrates

Marine water invertebrates

Effect concentration:

24 420 µg/L

Additional information

Freshwater

For freshwater, there were three studies available with Daphnia magna as a test species; two studies with InCl3 as toxicant and one study used Indium nitrate as toxicant.

Addition of In at higher loading (i.e. > 10 mg InCl3/L) causes a pH effect, which could influence the ecotoxicity results. Therefore, there were two studies conducted with Daphnia magna as a test species where in a first study (Aecom 2012b) pH was adjusted to test conditions and in a second study (Aecom 2012b) pH was not adjusted. The study with the unadjusted pH (lower pH shift in the higher In concentrations) had a 8.5 times lower LC50 compared to the adjusted pH test. As the higher In concentrations in the unadjusted pH tests had pH lower than 4.5, the LC50 of the adjusted pH test was used as an appropriate toxicity endpoint for acute freshwater toxicity tests. Zurita et al. (2007) examined the acute effect of Indium nitrate on Daphnia magna. The LC50 was 26220 µg In/L. In this study pH was not reported; although the higher loading could lead to a pH drop which decreases the LC50.

The results of the different tests with Daphnia magna are shown in the table below:

	pH adjusted conditions (Aecom 2012b)	pH adjusted conditions (Aecom 2012b)	pH non-adjusted conditions (Aecom 2012b)	pH non-adjusted conditions (Aecom 2012b)	pH non-adjusted conditions (Zurita 2007)
	µg total In /L	µg InCl3/L	µg total In/L	µg InCl3/L	µg In/L
LC50	>455500	>877293	53260	102579	31920
NOEC	455500	877293	35000	81050	11400 (after 48-h exp.)
LOEC	>455500	>877293	81050	156102	ND

pH was only controlled in the Aecom (2012b) study with pH adjustment, these LC50 and NOEC were used for classification of In compounds.

Borgmann et al. (2005) conducted two test with a different hardness (soft water and tap water). The LC50 was > 3150 µg In/L in the tapwater test and > 1000 µg In/L in the soft water test. Although these tests were conducted with Hyellella azteca (sediment species), the results indicate that hardness could influence the ecotoxicity results of Indium.

Marine

In the marine tests (3 species) (Onikura et al., 2008), information on pH and In measurements were not available. Although the tests were not according to standard protocols, the studies are of good quality with a lowest LC50 of 24420 mg In/L.