Titanium dioxide

Short-term toxicity to fish

Description of key information

Dispersions of microsized TiO2 are not acutely toxic to fish up to at least 1000 mg/L (LC50 > 1000 mg/L) and up to 10,000 mg/L (LC50: > 10,000 mg/L) in fresh- and saltwater, respectively. Considering the low solubility of microsized TiO2, it is concluded that microsized TiO2 is not acutely toxic up to its solubility limit.

Dispersed nanosized TiO2 is not acutely toxic to fish with unbounded LC50 values ranging from >1 mg/L to >100 mg/L in freshwater.

Additional information

Microsized TiO2:

Unbounded 96 h LC50 values of > 1000 mg/L (nominal) for Pimephales promelas, > 100 mg/L (nominal) for Oncorhynchus mykiss and > 300 mg/L (nominal) for Danio rerio in freshwater were derived in acute toxicity tests of dispersed microsized titanium dioxide (Hutton et al. 1992a-c, Turner et al. 2006, Mahjoubian et al. 2021). Sub-chronic toxicity tests with dispersed microsized titanium dioxide generated unbounded 14 d LC50 values of > 0.87 and > 1.1 mg/L (measured) for Oncorhynchus mykiss and Danio rerio in freshwater (Boyle et al. 2013, Ramsden et al. 2013). One supporting study by Wyrwoll et al (2014) on fish embryos points to a lack of acute toxicity of dispersed microsized TiO2 up to 100 mg/L (72 h LC50 > 100 mg/L). An unbounded 96 h LC50 of > 10,000 mg/L (nominal) was observed for Cyprinodon variegatus exposed to dispersed microsized TiO2 in saltwater (Thomson et al. 2007).

 

Transformation dissolution data of different microsized TiO2 materials indicate a low solubility in environmental media as dissolved Ti concentrations after 28 d were below the respective LOD/LOQ (< 0.11 / < 0.34 µg Ti/L). Hence, the acute fish experiments with microsized TiO2 were performed at TiO2 water concentrations above the solubility limit of microsized TiO2. It is further concluded that microsized TiO2 is not acutely toxic to freshwater fish up to its solubility limit.

 

Nanosized TiO2:

Unbounded 96 h LC50 values of > 100 mg/L (nominal) were reported for the toxicity of nanosized TiO2 dispersions and Carassius auratus and Oncorhynchus mykiss (Ates et al. 2013, Turner et al. 2006). Furthermore, unbounded LC50s of > 1 mg TiO2/L (measured) were derived for Oncorhynchus mykiss and Danio rerio exposed to dispersed nanosized TiO2 for 14 days in three sub-chronic studies (Boyle et al. 2013, Federici et al. 2007, and Ramsden et al. 2013). Acute toxicity tests with embryos of Danio rerio generated 72 h and 96 h LC50 values of > 100 mg/L (nominal) for nanosized TiO2 dispersions (Wyrwoll et al. 2014, Clemente et al. 2014).

 

Five supporting studies further indicate that nano-TiO2 dispersions are not acutely toxic to freshwater fish up to at least 100 mg/L since LC50 values ranged from > 10 mg/L to at least > 100 mg/L (nominal, dispersed) for adult and embryonic life stages of Danio rerio , Oryzias latipes and Clarias gariepinus (Griffit et al. 2008, Li et al. 2014, Yang et al. 2013, and Ma et al. 2012, Tuncsoy 2021). However, the latter tests were performed with inappropriate life stages and for a too short duration (Li et al. 2014), the provided information on methods and validity was not sufficient (Yang et al. 2013), the tests were performed at a water hardness that does not meet guideline criteria (Ma et al. 2012), or the tests used a reduced number of specimens and a biomass loading that exceeds the guideline recommendations (Tuncsoy 2021).

 

Marine data do not exist.

 

Based on a weight of evidence approach, dispersed nano- and microsized TiO2 is not acutely toxic to fish since unbounded LC50 values of > 100 mg and > 1000 mg TiO2/L were derived in freshwater, respectively. Further, an unbounded LC50 value of > 10,000 mg/L for dispersed microsized TiO2 in saltwater points to a low potential for acute toxicity to fish. Considering the low solubility of microsized TiO2, it is further concluded that microsized TiO2 is not acutely toxic up to its solubility limit.