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Titanium tetrachloride is not directly emitted to soils but may reach terrestrial compartment e.g. via air. As the material hydrolyzes rapidly in the presence of any air moisture to non-poisonous titanium dioxide (CAS 13463-67-7) and hydrogen chloride (CAS 7647-01-0 ), only its transformation products are relevant for the hazard assessment.

The hydrogen chloride is released in a fourfold molar amount during the rapid hydrolysis of titanium tetrachloride. It will dissociate fully in hydronium ions (CAS 12586-59-3) and chlorides (CAS 16887-00-6), of which the latter is not a harmful substance and in significant levels omnipresent in the environment. The ionized chlorides will not stay in soils as they are very mobile and will not reach the terrestrial environment from water. In case of unlikely direct exposure of soil, effects may occur due to pH reduction caused by the dissociation of the hydrogen chloride. Such effects are not substance specific and would occur only if the soil exposure would exceed the buffering capacity. Thus these transformation products are considered not relevant for the hazard assessment.

The other hydrolysis product, titanium dioxide (CAS 13463-67-7), is released isomolar to titanium tetrachloride. Exposure of the terrestrial compartments via air is unlikely due to its fugacity properties but may occur via dust. Air hydrolysis of titanium tetrachloride reveals titanium dioxide particles 0.4 to 0.7 µm scale. Even in the unlikely case that relevant amounts of titanium tetrachloride would enter soils, the pore water contact would immediately induce the hydrolysis reaction. In the direct contact with the soil minerals the formation of pure crystalline nanoparticles seems unlikely, as foreign atoms may be incorporated and/or the titanium may be incorporated into the mineral soil matrix. Titanium dioxide is considered inert and non-poisonous in the relevant isomolar levels. This is in accordance with read across from experimental data on titanium dioxide effects to terrestrial plants, micro-organisms, earthworms, and arthropods (ARCADIS 2008, Jemec et al 2008, Heckman et al 2008, and Velzeboer et al 2008). Heckman et al 2008 report some effect of 1000 mg/kg nanoscaled material to earthworm reproduction, which lack at the bulk material. For the above given reasons these effects were regarded irrelevant for the hazard assessment of titanium tetrachloride as it is assessed unlikely that its environmental transformation reveals nanocrystalline titanium dioxide particles.

Thus there is no evidence that any specific mode of action is relevant and in consequence the “Hazard Category 1” (ECHA 2008 Guidance on information requirements and chemical safety assessment Table R.7.11-2, p 131) applies for the titanium dioxide. Accordingly the risk can be assessed on the basis of isomolar titanium dioxide effects according to the Equilibrium Partitioning Method (EPM) and no testing is required. As no aquatic toxicity is known and no threshold levels exist, the EPM predicts no toxicity to soil organisms. Due to the lack of effects no starting points for the calculation of terrestric PNEC is given.

In conclusion titanium tetrachloride and its hydrolysis products do not pose a risk to the terrestrial life.