(ethyl acetoacetato-O1',O3)(pentane-2,4-dionato-O,O')[propane-1,3-diolato(2-)-O,O']titanium

Endpoint summary

Description of key information

Freshwater short term aquatic toxicity data were available for three trophic levels: fish, invertebrates and algae. In all acute tests the L(E)C50 is greater than the highest tested concentration of 5 mg/L (nominal). Based on effects on the growth rate a NOEC of 0.5 mg/L (nominal) was detected for algae. The toxicity of the test substance to microorganisms resulted in a NOEC of 180 mg/L (nominal).

Additional information

Water solubility of 1.01 g/L at pH 4 was measured in a test according to OECD 105. In this test the solubility was measured based on soluble titanium. However, other observations made in the water solubility test indicate that the test item undergoes hydrolysis or alternative transformation mechanisms. It is assumed that the water solubility decreases with an increasing pH value. In preliminary water solubility investigations conducted within the ecotoxicological tests (with fish, daphnia and algae) a limit of water solubility of approximately 3.5 mg/L at a pH value of about 7.5 was obtained. 

A hydrolysis test was not conducted. No evaluation of the hydrolytic stability of the test item in aqueous media was possible. This was due to the absence of a suitable substance specific analytical method with which to evaluate the intact test item chelate. Based on the findings in the water solubility study with this substance and based on knowledge from structurally-related organo-titanium substances (table 1) , the test item is assumed to be hydrolytically unstable and will therefore be subject to rapid hydrolysis in aqueous conditions. 

Table 1: Hydrolysis of structurally-related organo-titanium substances (Source: REACH registration dossiers disseminated on the ECHA web page)

EC Name	CAS	Hydrolysis
Bis(2-ethylhexan-1-olato)bis(pentane-2,4-dionato-O,O')titanium	94233-27-9	<= 30 min at pH 10 and 30°C
Bis(ethyl acetoacetato-O1',O3)bis(2-methylpropan-1-olato)titanium	83877-91-2	<= 10 min at pH 4, 7 and 9 at 25°C
Bis(ethyl acetoacetato-O1',O3)bis(propan-2-olato)titanium	27858-32-8	<= 10 min at pH 4, 7 and 9 at 25°C
Bis(pentane-2,4-dionato-O,O')bis(propan-2-olato)titanium	17927-72-9	1.491h at 25°C
Butyl (dialkyloxy(dibutoxyphosphoryloxy))titanium(trialkyloxy)titanium phosphate	109037-78-7	readily hydrolysable
Ethoxybis(pentane-2,4-dionato-O,O')(propan-2-olato)titanium	68586-02-7	<= 30 min at pH 1.2, 4, 7 and 10 at 30°C
Tetrakis(2-ethylhexane-1,3-diolato)titanium	5575-43-9	<= 10 min at pH 4, 7 and < 5 minutes at pH 9 at 25 °C
Tris(isooctadecanoato-O)(propan-2-olato)titanium	61417-49-0	<=1hr
Titanium tetra(octanolate), branched and linear	83897-91-0	<= 10 min at pH 7 and pH 9, and < 5 min at pH 4 at 25 °C
Titanium, diethylene glycol ethylene glycol triisopropanolamine complexes	68784-47-4	<= 30 min at pH 4.4 at 25°C

 

The expected hydrolysis products are Acetylacetone (CAS 123-54-6), ethyl acetoacetate (CAS 141-97-9), 1,3-propanediol (CAS 504-63-2) and titanium hydroxide. As an insoluble precipitate, titanium hydroxide is lacking bioavailability and therefore considered not relevant in aqueous conditions. The other three hydrolysis products are all registered under REACH. They are evaluated to be rapidly biodegradable and have no risk of bioaccumulation based on low log Kow values. All three hydrolysis products are not classified as hazardous to the environment.

 

The ecotoxicological tests (fish, Daphnia, algae) were all conducted with appropriate high concentrations of the test substance (nominal 5 mg/L). Because of the nature of the substance, verification of exposure concentrations was based on the measured levels of total dissolved titanium in the samples taken during the test, from which the measured levels of the test item were calculated based on their theoretical titanium content. It was not possible to identify if the titanium measured originated from the parent substance or the degradation product. Given the decline in measured test concentrations observed in the ectoxicological test, it was considered appropriate to calculate the results based on the geometric mean measured test concentration (calculated from the test item`s theoretical titanium concentration) in order to give a “worst case” analysis of the data. However, calculations based on the titanium concentration could be misleading, as only the dissolved titanium concentration can be detected. Titanium hydroxide is essentially insoluble and will thus precipitate from the water phase over time. The detected concentration based on the theoretical titanium concentration varies from study to study:

 

5 mg/L =         0.0073mg/L     [meas. (geom. mean)] after48hours (Daphnia test, limit test)

5 mg/L =         3.4 mg/L         [meas. (geom. mean)] after72hours (Algae test, highest conc. tested)

5 mg/L =         0.13 mg/L       [meas. (geom. mean)] after96hours (Fish test, limit test)

 

 

Additionally, the measured titanium concentration does not necessarily correlate with the concentration of the hydrolysis products (as listed above), which are all soluble in water. Hence, the concentration of the organic hydrolysis products in water is likely to be much higher than the titanium concentration in water.

In conclusion, the applied analytical method is not able to:

-      differentiate between titanium from the parent substance and from the hydrolysed product

-      estimate the concentration of the hydrolyzed product in the water phase due to differing properties between titanium and its ligands;

and can be considered to be not appropriate and the measured concentration to be not valid.

 

Therefore, the nominal concentrations are used for PNEC calculation and classification. This approach is nevertheless “worst case”, as in the limit test with Daphnia and fish, no effects were observed at the concentration tested. In the study with algae, inhibition of growth was observed, but it was not possible to calculate an ErC50 value at the limit of water solubility (3.5 mg/L), as not more than 26% inhibition of growth rate occurred.

 

Based on the rapid hydrolysis, the intrinsic properties lie in the degradation products, which show no hazard to the environment.