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Short-term toxicity to aquatic invertebrates

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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. A weight of evidence approach based on studies on titanium dioxide is being proposed. Based on the information available 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 invertebrates.

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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 (< 0.1 μg/L); excess titanium dioxide will be present as insoluble matter.

In the study of Bazin (1994), Daphnia were getting exposed to the WAF of the target chemical at a loading rate of 100 mg/l. The EL50 (48h) for titanium oxide sulphate is > 100ppm (weight/weight) (mg/kg). Therefore it is to be concluded that Bazin in fact analysed the effect of titanium dioxide.

For complete assessment of the effects of titanium dioxide on Daphnia, a weight of evidence approach is being suggested, including also the studies on final hydrolysis product titanium dioxide. All studies uniformly show the absence of short-term effects on Daphnia 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 Daphnia might occur as a result of fouling, smothering or coating with high loadings of titanium dioxide precipitate, however such effects are not to be attributed to toxic properties of the substance.

It is concluded that final hydrolysis transformation product titanium dioxide does not exhibit short-term toxic effects to Daphnia at the level of its water solubility in addition with suspended microdisperse matter in excess, even if ingested.

Concerning the target compound titanium oxysulfate itself, the increase of acidity caused by the rapid hydrolysis reaction to form the other final hydrolysis product sulphuric acid is of no relevance for environmental risk assessment under REACH. Within the environmentally relevant pH range sulfuric acid species are being neutralised and thus rendered harmless to biota.