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In contact with water, Zirconium tetrachloride decomposes instantaneously into HCl and ZrOCl2. Then, ZrOCl2 is also not stable in water and hydrolyses rapidly and precipitates into Zirconium dioxide and Hydrochloric acid, under environmental conditions. As HCl is not toxic to terrestrial organisms (only pH effect), it will not be considered as a relevant degradation product to assess ZrCl4 toxicity. Therefore, as for other Zirconium compounds, the relevant degardation product for a read across purpose for the terrestrial toxicity is ZrO2 or any other Zr compounds leading to ZrO2 formation.

Considering the conclusion on adsorption/ desorption endpoint, zirconium compounds have a strong affinity for the soil particle (high Koc values). This leads to a large decrease in the availability of zirconium to the organisms that live in the soil compartment (bioavailability).

No information is available from the literature on toxicity of Zr compounds to terrestrial organisms.

Concerning the effect on plant, the study available displayed no adverse effect on tomato and pea seedlings (ca. 21 days old) exposed for 7 days to two different soils contaminated with either a soluble Zr compound (ZrOCl2 or Zr acetate) or an insoluble Zr compound (Zr(OH)4). Unbound NOEC values were obtained for all experiments. The highest unbound NOEC was >= 703.4 mg Zr/kgdw (i.e. 1796.6 mg ZrCl4/kg dw) for the acidic soil (417.4 mg Zr/kg background) and the lowest unbound NOEC was >= 450 mg Zr/kgdw (i.e 1149.4 mg ZrCl4/kgdw) for the calcareous soil (164 mg Zr/kg background), both soils amended with 286 mg Zr/kg Zr(OH)4.

Concerning the toxicity to birds, no likely exposure is expected and this endpoint has been waived.

In conclusion, considering all this information and the exposure assessment presented in the CSR that reveals very little likelihood of exposure of the terrestrial compartment (little deposition and no sludge application to agricultural land) no testing proposal is made for terrestrial toxicity of ZrCl4.