Titanium tetrakis(2-ethylhexanolate)

Endpoint summary

Additional information

Titanium tetrakis(2-ethylhexanolate) is an organometallic substance which is hydrolytically unstable.The hydrolytic stability was tested in buffered aqueous solutions at pH 4.0, 7.0, and 9.0 at 25°C for 40 minutes. Based on the results, half-life of substance was < 10 minutes at pH 4 and 7, and < 5 minutes at pH 9 (Brekelmans M.J.C 2013). The progress of the hydrolysis was followed by monitoring 2-ethylhexanol (2-EH), the main degradation product of the substance. Titanium is a solid precipitate of the substance present as hydrated titanium dioxide in water after hydrolysis.This decomposition product (TiO2) is not classified hazardous to human health or the environment. Furthermore, Ti compounds are not expected to bioconcentrate in soils, sediments or aquatic organisms (WHO 1982). As an insoluble precipitate, it is also lacking bioavailability, and therefore not relevant to be considered further in CSA.

Because of the rapid abiotic degradation, water solubility, biodegradation and partition coefficient (Kow) cannot be determined for the substance itself. In addition, the intrinsic properties of aquatic toxicity are related to the main degradation product (2 -EH) of this substance. This was demonstrated by the aquatic toxicity studies (daphnia and algae) conducted for the analogue category member titanium tetra(octanolate), branched and linear CAS 68526 -83 -0 ( Tobor-Kaplon 2013). The category justification is presented in the Annex I of this CSR, and the results of this analogue substance are included to the weight of evidence on toxicity of titanium tetrakis(2-ethylhexanolate) (see section 7.1 of the CSR).

This analogue substance (titanium tetra(octanolate), branched and linear of the target substance hydrolyzed immediately in aqueous test media releasing isooctyl alcohols mixture with the hydrated titanium oxide precipitating out of the test solution. Due to the rapid hydrolysis, it was considered that any toxicity would be due to the presence of isooctyl alcohols and not the parent test item. Therefore, the toxicity to the freshwater invertebrates and algae were investigated based on the measured isooctyl alcohol concentrations only.This read-across substance is an analogue substance grouped together with the target substance into the category of highly water reactive titanates. It contains commercial solvent (Alcohols C7 -9-iso, C8-rich, CAS no 68526 -83 -0). This solvent contains 93 % of isooctanol being also an analogue substance with 2 -ethylhexanol; an isomer of octyl alcohol and the main degradation product of the target substance.

Based on these study results it is justified to conclude that the ecotoxicity of titanium tetrakis(2-ethylhexanolate) is related to the toxicity of 2-ethylhexanol released, and testing of this substance is unnecessary. Instead the read-across data from the main degradation product (2 -EH) and the analogue category member was used as a key value in CSA (see section 7.1 of CSR). The toxicity results do not indicate the need to classify this substance hazardous to the environment.

As the rapid hydrolysis is the driving force for the fate and pathways of this substance, the abiotic degradation can be used to demonstrate fast degradation for this substance. This is justified as all decomposition products have been identified. The most relevant degradation product (2 -EH) is also known to be readily biodegradable (> 79 % to 100 % in 14 days, NITE 2002).

The transport and distribution of titanium tetrakis(2-ethylhexanolate) was evaluated based on its reactivity. Because of high reactivity, most of the physical chemical properties of the target substance are not technically feasible to determine. Therefore, the fate and pathways are related to the main degradation product.

The vapor pressure of titanium tetrakis(2-ethylhexanolate) cannot be determined as it decomposes during testing (OECD 104, Brekelmans M. J. C. 2013). If released to air, this substance will release 2-ethylhexanol (2 -EH). A vapor pressure of 0.1 kPa at 20 ˚C and Henry's law constant of 14.8 Pa m³/mol indicate that 2 -EH will be volatile in the ambient atmosphere. Vapor-phase will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 1.5 days (HSDB 2012).

Based on the composition of of titanium tetrakis(2-ethylhexanolate) and the properties of the main degradation product, this titanate in the atmosphere has no potential for stratospheric ozone depletion for structural reasons. It does not contain any halogens. Therefore there is no reason for any hazard classification under the CLP regulation 1272/2008 for atmospheric environment (the ozone layer).

If released to soil, because of soil moisture this titanate will decompose. The adsorption coefficient of 2-ethylhexanol (Koc value of 35.28 L/kg), estimated by using KOCWIN v.2.00 is used in CSA for the target substance (US EPA 2012). 2 -EH released from this substance is expected to have very high mobility based upon an estimated Koc. In addition, the water solubility of 2 -EH (880 mg/l, Amidon GL et al. 1974) indicates high mobility in soil, while the other inorganic degradation product (hydrated titanium dioxide) is insoluble (O'Neil et al. 2006). Vapor pressure (0.1 kPa) and Henry's Law constant (14.8 Pa m³/mol) suggest that some volatilization may occur from both dry and moist soil.

If released into water, a complete hydrolysis of titanium tetrakis(2-ethylhexanolate) will take place with no significant reaction products other than 2 -ethylhexanol (2 -EH) and hydrated titanium dioxide (Brekelmans M.J.C 2013). Again, 2 -EH is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected based upon the Henry's Law constant. Biodegradation is the most important fate process of 2-ethylhexanol.

Titanium tetrakis(2-ethylhexanolate) has no strong binding behaviour to soil particles as the partition coefficient of 2-ethylhexanol (log Kow 2.9) is well below 4. Since the target substance is hydrolytically unstable, use of water is avoided in the use applications. Therefore, no emissions to a sewage treatment plant (STP) are expected. Discharge to STP is relevant only in one use application when the target substance is used as a catalyst in industrial esterification processes. In this use application, water is used to remove the catalyst from the process. The discharge to STP is related to the degradation products of this substance as the hydrolysis will take place, and 2-ethylhexanol and TiO₂ are released to water compartment. Because of this mechanistic reasoning for read-across, the relevant properties of 2-ethylhexanol, instead of measured values of the target substance, are used as the key values for environmental and human health exposure assessment (see sections 9 & 10 of CSR).

Based on the decomposition and the properties of the degradation products, titanium tetrakis(2-ethylhexanolate) has neither persistence potential nor sorption potential. Therefore, the soil/sediment simulation testing does not need to be further considered in CSA. This substance is not fulfilling the criteria to be classified as a PBT or vPvB substance. Thus, CSA indicates that further testing of long-term aquatic effects or terrestrial toxicity testing is also unnecessary. In addition, testing is scientifically unjustified as the direct exposure to aquatic or terrestrial compartment is unlikely based on the exposure scenarios (see section 9&10 of CSR). Discharge to STP is only relevant in industrial esterification processes when water is used to remove the catalyst from the process. The possible spreading of STP sewage sludge as fertilizer to soil is expected to cause low hazard to soil organisms as the degradation products are readily biodegradable (2-ethylhexanol) and non-toxic to environment. Indirect emissions to environment are occuring only via atmospheric deposits.

There are all together eight different organometallic titanates from the same manufacturer which are registered at the same tonnage band. As all these titanates are hydrolytically unstable substances and they have structural similarities, two group categories have been formed. Because of behavioral similarities some properties of these titanates are evaluated by using read-across data from the category members as well as from the degradation products. The category and read-across justifications with the data matrices are presented in the Annexes of the CSR.