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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Target substance titanium oxide sulphate itself is unstable in water and produces insoluble titanium oxide after rapid hydrolysis. Based on the information available from the key study on the target chemical itself and from two supporting studies on final hydrolysis product TiO2, it can be concluded that neither target compound titanium oxide sulphate nor the final hydrolysis transformation products titanium dioxide and sulphuric acid (after neutralisation) exhibit acute toxic effects to aquatic algae.

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Additional information

Titanium oxide sulphate rapidly hydrolyses in water, resulting in the formation of titanium dioxide and causing an increase in acidity. Titanium dioxide is very poorly soluble in water at neutral pH (< 0.1 μg/L), thus excess titanium dioxide will be present as insoluble matter.

In the study of Egeler (2010) on target chemical titanium oxide sulphate itself, after pH adjustment, and precipitation of TiO2, the measured concentrations of titanium in the liquid phase were below the limit of detection of 0.0027 mg/L in all samples. The results of the study demonstrate that under pH-adjusted conditions the no-observed effect loading rate (NOELR) forPseudokirchneriella subcapitatafor the parameters yield and growth rate is ≥ the water-accommodated fraction (WAF) at a loading rate of 100 mg test item/L (nominal concentration).Therefore it is to be concluded that Egeler in fact analysed the effects of titanium dioxide.

Furthermore the two supporting studies uniformly show the absence of adverse effects on algae at nominal concentrations that are several orders of magnitude higher than the soluble concentration plus additional load of suspended microdisperse matter in excess. Physical effects on the algae caused by TiO2 particles, such as adsorption and shading, might occur, however such effects are not to be attributed to toxic properties of the substance.

Based on the information available from the key study on the target chemical itself and from two supporting studies on final hydrolysis product TiO2, it can be concluded that neither target compound titanium oxide sulphate nor the final hydrolysis transformation products titanium dioxide and sulphuric acid (after neutralisation) exhibit acute toxic effects to aquatic algae.