Titanium tetrabutanolate

Endpoint summary

Additional information

Titanium tetrabutanolate is hydrolytically unstable. The progress of the hydrolysis was followed by monitoring n-butanol, the main degradation product of the substance (Brekelmans 2013). The other non-hazardous degradation product (hydrated titanium oxide) is insoluble lacking bioavailability in aquatic environment, and therefore not further considered in CSA.

Because of the rapid hydrolysis, the intrinsic properties of aquatic toxicity are related to the main degradation product (n-butanol).Therefore, a short-term and long-term toxicity studies for the target substance were considered unjustified. Key studies for the analogue category member (titanium tetraisopropanolate CAS no. 546 -68 -9) justify that these organometallic titanates hydrolyse during toxicity testing and the aquatic toxicity is similar to the alcohol released in water. Due to the rapid hydrolysis in aqueous test media, the degradation products (isopropyl alcohol and hydrated titanium dioxides) toxicity to the freshwater invertebrates and algae were investigated based on the measured isopropyl alcohol concentrations and the equivalent test item concentrations in these studies conducted for this analogue category member.

Two categories of highly water reactive titanates and moderately water reactive titanates are formed from the eight analogue organometallic titanates, because they all are hydrolytically unstable, and have mechanistic reasoning for read-across from the degradation products within the categories. The source substance for this target substance (titanium tetrabutanolate) is n-butanol. The analogue organometallic titanate (bis(ethyl acetoacetato-O1', O3') bis(2 -methylpropan-1 -olato)titanium from the category of moderately water reactive titanates contains and releases 2-methylpropanol, which is an analogue to n-butanol released from titanium tetrabutanolate. The structural analogy of 2-methylpropanol (CAS no 78 -83 -1) and n-butanol (CAS no 71-36-3) has also used to support the environmental hazard assessments of these alcohols in OECD SIDS initial assessment reports published by UNEP ( UNEP publications 2001 & 2004). Therefore, the toxicity of 2-methylpropanol is used in the weight of evidence approach to evaluate the toxicity of the target substance together with n-butanol data.

Based on the rapid hydrolysis of this substance in water, the short-term and long-term aquatic toxicity testing was considered scientifically unjustified and the read-across data from the main degradation product (n-butanol) and the degradation product of the analogue category member (2 -methylpropanol) was used as a key value in CSA. Category and read-across justifications are presented in the annexes of the CSR.

Short-term toxicity to fish:

•96-h LC50 (mortality) to Pimephales promelas, 1825 mg/L based on measured/nominal concentrations (read-across from n-butanol; Mattson et al. 1976 and Veith et al. 1983)

Short term and long-term toxicity to invertebrates:

•48-hour LC50 (immobilisation) to Daphnia magna, 1300 mg/L based on nominal concentrations (read-across from 2-methylpropanol; Elnabarawy et al. 1986)

•21-d NOEC (reproduction) to Daphnia magna, 4 mg/L based on nominal concentrations (read-across from 2 -methylpropanol; Kuehn et al. 1989)

Toxicity to algae:

•The 96-h EC50 (growth rate) to Pseudokirchnerella subcapitata, 225 mg/l (95% CL: 204 -246 mg/l) based on measured concentrations (read-across from n-butanol; UNEP 2004)

•The 96-h EC10 to Pseudokirchnerella subcapitata, 134 mg/l (95% CKL: 124 -167 mg/l) based on measured concentrations (read-across from n-butanol; UNEP 2004)

Toxicity to microorganisms:

•16 h-Toxicity Threshold (cell multiplication) to Pseudomonas putida, 650 mg/l based on nominal concentrations (DIN 38412 part 8; read-across from n-butanol; Bringmann &Kuhn 1980)