Titanium dioxide

Toxicity to terrestrial arthropods

Description of key information

 Data are available for the effect of different upgraded ilmenite (UGI, >80% TiO2) slags on survival and reproduction of the terrestrial arthropod Folsomia candida. Conservatively, a long-term NOEC of 1000 mg/kg dw and a chronic LOEC of 3000 mg/kg dw is derived based on observed effects. In sum, TiO2 appears to have a low potential for toxicity to soil arthropods.

Additional information

Data are available for the effect of different upgraded ilmenite slags (UGI, >80% TiO2) on survival and reproduction of the terrestrial arthropod Folsomia candida. Conservatively, a long-term NOEC of 1000 mg/kg dw and a chronic LOEC of 3000 mg/kg dw is derived. Upgraded ilmenites (UGI) consist primarily (> 80%) of titanate, i.e., TiO2 with Fe, Al, Si, Mg and other metals, and are poorly soluble and not biodegradable. The transformation/dissolution of three UGI products at loadings of up to 100 mg/L over 24 h did not result in any significant release of titanium (Skeaff, 2007). Bulk and nano-TiO2 forms are also poorly soluble in environmental media (Brouwers, 2009; Klawonn, 2017 a-f). Based on similarity in composition and the same poor solubility of UGI and TiO2, read-across of ecotoxicological data from UGI to TiO2 is justified.

One supporting study on the acute toxicity of microsized TiO2 to Porcellio scaber is available and indicates that microsized TiO2 has a low toxic potential to terrestrial arthropods: Jemec et al. (2016) performed two non-standardized leaves-consumption tests, in which adult animals of both sexes of Porcellio scaber were offered two pieces of the same hazelnut leave either individually or in groups of 10 organisms for 14 d. Both pieces were either treated with deionized water (controls) or one piece was treated with deionized water and the other piece was treated with a suspension of micro-sized aluminium-zirconium coated TiO2 (1000 mg/kg dw leave). Consumption of control and treated leaves did not significantly differ (unbounded 14 d NOEC ≥ 1000 mg/kg dw leave, nominal), indicating that isopods neither avoided nor selected TiO2 treated leaves after 14 d of exposure to both treatments. Exposure occurred via food and not via the soil. Therefore, the results of this test are considered supporting data.

Furthermore, one supporting study on the acute toxicity of nanosized TiO2 to Porcellio scaber, is available. In this study, sonicated and non-sonicated dispersions of a nano-sized TiO2 material (15 nm, anatase) applied to dry leaves did not affect weight change, feeding rate, food assimilation efficiency, and survival of Porcellio scaber after 3 days of dietary exposure in a non-standardized test. Derived 3 d NOEC values were 3000 mg/kg diet dw. Furthermore, inconsistent dose-response relationships were observed for antioxidant enzyme activities at these effect levels. Exposure occurred via the food and not via the soil. Therefore, the results of this test are not considered for hazard assessment.

In sum, nano- and microsized TiO2 appears to have a low potential for toxicity to soil arthropods based on data available for springtails and isopods.