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Toxicity to aquatic algae and cyanobacteria

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The acute toxicity to aquatic algae was tested using titanium dioxide and titanium trichloride. Hence, for titanium carbide this endpoint is derived by read-across from titanium dioxide and titanium trichloride.
Titanium compounds are of low toxicity for algae. Due to the insolubility of titanium carbide, toxic effects for aquatic algae are not expected to arise from the substance.

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Additional information

Two reliable key studies for toxicity of titanium dioxide to aquatic algae are available. The first study was conducted by Wahrheit et al. (2007) who investigated the toxicity of fine TiO2 (380 nm) and ultrafine TiO2 (140 nm) to Pseudokirchneriella subcapitata in accordance with OECD guideline 201. The test substance were used at nominal test concentrations of 0 (control), 0.01, 0.1, 1.0, 10, 100 mg TiO2/L. The ErC50 for fine and ultrafine TiO2 in Pseudokirchneriella subcapitata was determined to be 61 and 87 mg/L, respectively.


This relatively low toxicity of TiO2 to algae is further supported by the second key study by Hund-Rinke & Simon (2006) who investigated toxic effects of nano-size TiO2 (25 nm and 100 nm) to Desmodesmus subspicatus in a test according to OECD 201. Both particle size materials were investigated as such and in form of additionally cleaned material. Actual particle size distribution was not verified. The 48-h ErC50 values for both products and treatments were calculated to be > 50 mg/L. Respective 48-h ErC10 values ranged between 9.9 mg/L and 47 mg/L.

In addition, the results referenced above are supported by a study investigating 90-d exposure of Chlorella vulgaris to different concentrations of TiCl3 (Den Dooren, 1965). This exposure resulted in a 90-d NOEC and LOEC of TiCl3 for Chlorella vulgaris of 6.5 mg Ti/L and 16 mg Ti/L, respectively.


Velzeboer et al. (2008) investigated the influence of 100 mg TiO2/L (50-150 nm) on the efficiency of photosynthesis of Pseudokirchneriella subcapitata after exposure for 4.5 h. TiO2 did not result in a decrease of photosynthesis by the algae.


Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide and titanium trichloride (the source substances), the resulting toxicity potential would also be expected to be lower. Therefore, the dose descriptors are expected to be sufficiently high for the target substance, and read-across to the source chemical is adequately protective. In fact, (eco-)toxicologically relevant release of Ti ions from titanium carbide is not expected as the concentration of soluble Ti ions was below the method detection limit (< 0.4 µg/L) in the T/D test. Thus, TiC is considered to be practically insoluble. Release of Ti ions to any ecotoxicologically relevant extent (and potential subsequent formation of soluble and/or insoluble Ti compounds) is not expected. Therefore, toxic effects for aquatic algae are not expected to arise from TiC.