Bis(ethyl acetoacetato-O1',O3)bis(2-methylpropan-1-olato)titanium

Endpoint summary

Additional information

This substance is an organometallic substance which is hydrolytically unstable having a half-life less than 10 minutes at 25 deg. C.

The hydrolytic stability was tested in buffered aqueous solutions at pH 4.0, 7.0, and 9.0 at temperatures of 20°C, 30°C, and 50°C for 40 minutes (Brekelmans 2013). The progress of the hydrolysis was followed by monitoring 2 -methylpropanol (IBA) and ethyl acetoacetate (EAA), the main degradation products 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 products (IBA and EAA) of this substance. This was demonstrated by the aquatic toxicity studies (daphnia and algae) conducted for this substance according to the OECD guidelines and in accordance with GLP (Tobor-Kaplon 2013). The test item hydrolyzed immediately in aqueous test media releasing IBA and EAA 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 IBA and EAA not parent test item. Therefore, the toxicity to the freshwater invertebrates and algae were investigated based on the measured IBA and EAA concentrations only.

Based on these study results conducted for the substance, the short-term toxicity testing to other organisms (fish) was considered scientifically unjustified. Instead supporting read-across data from the main degradation products was used as a key value in CSA (see section 7.1 of CSR). The toxicity results of the target substance and the decomposition products 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 (Brekelmans 2013). The main degradation products (IBA and EAA) are also known to be readily biodegradable (> 72 % at 20-d biodegradation test, Price et al. 1974, and 66 % at 28 days; European Chemicals Bureau 2002) and not classified as hazardous to the environment. The information on the short-term aquatic toxicity of these degradation products were used as supporting data in CSA. The long-term aquatic toxicity was available for reproduction toxicity of 2 -methylpropanol to invertebrates (D.magna). No further long-term toxicity studies were considered necessary for this substance based on the low short-term and long-term toxicity level of the degradation products, and their ready biodegradability.

The transport and distribution was evaluated based on substance's reactivity. Because of instability in water, 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 most critical degradation product 2 -methylpropanol (IBA). For identification of the most critical degradation product regarding exposure to environment, the toxicity and environmental fate properties of IBA and EAA were evaluated.

After hydrolysis amount of EAA released to water is approximately 2 times the amount of IBA. Both of the substances are non-hazardous to aquatic environment. IBA is more volatile than EAA, and its degradation is air is faster than for EAA. In water EAA decomposes further into degradation products. Overall, IBA is considered as the more critical degradation product regarding the environmental exposure. This is based on the higher volatility and the fact that release to air is the main exposure route to environment (section 9&10 of CSR).

The vapor pressure of the target substance cannot be determined as it decomposes during testing (OECD 104, Brekelmans 2013). If released to air, this substance will release 2 -methylpropanol (IBA) and ethyl acetoacetate (EAA). A vapor pressure of 10 hPa at 20.9 ˚C indicates that IBA will exist solely as a vapor in the ambient atmosphere. 2 -methylpropanol was selected as the most critical substance for overall exposure assessment as it is also more volatile than ethyl acetoacetate in terms of air emissions (vapour pressure of EAA; 1hPa at 20 deg. C).

Vapor-phase IBA 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 1.55 days (UNEP 2004). Direct photolysis of ethyl acetoacetate (EAA) in the atmosphere is not to be expected. However, gaseous EAA reacts in the atmosphere with hydroxyl radicals which have been formed photochemically.The calculated half-life of ethyl acetoacetate (EAA) for photochemical degradation amounts to 10.3 days (European Chemicals Bureau 2002).

Based on the composition of the target substance and the properties of the main degradation products, 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 releasing 2 -methylpropanol, ethyl acetoacetate and hydrated titanium dioxide. Because the overall CSA concentrates on the most critical degradation product, the adsorption coefficient of 2 -methylpropanol (Koc value of 2.919 L/kg), estimated by using KOCWIN v.2.00 is used in CSA for the target substance (US EPA 2012). 2 -methylpropanol released from this substance is expected to have very high mobility based upon an estimated Koc. In addition, the water solubility of IBA (85 000 mg/l, HSDB 2012) indicates high mobility in soil. In addition, ethyl acetoacetate has low bindging potential to soil (Koc 14.125 L/kg) and high mobility in soil as it is soluble in water (110 g/l, CHemIDplus Lite 2012), while the inorganic degradation product (hydrated titanium dioxide) is insoluble (O'Neil et al. 2006). Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 1.19 Pa m³/mol of 2 -methylpropanol (IBA). IBA is expected to volatilize from dry soil surfaces based upon its vapor pressure.

If released into water, a complete hydrolysis will take place with no significant reaction products other than 2 -methylpropanol, ethyl acetoacetate and hydrated titanium dioxide (Brekelmans 2013). Again, the degradation products are not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected based upon this compound's Henry's Law constant. Biodegradation is expected to be an important fate process of the degradation products.

This titanate has no strong binding behaviour to soil particles as the partition coefficient of the organic degradation products (log Kow 0.76; IBA and 0.25; EAA) are well below 4. Since the target substance is highly hydrolytically unstable, use of water is avoided in the use applications. Therefore, no emissions to a sewage treatment plant (STP) are expected from industrial applications. Because of this mechanistic reasoning for read-across, the relevant properties of the most critical degradation product (IBA), instead of measured values of the target substance, are used as the key values for the exposure assessment (see sections 9 & 10 of CSR).

Based on the decomposition and the properties of the degradation products, this titanate 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 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). 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.