Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

The photodegradation of tributyl acetylcitrate in the atmosphere by reaction with OH radicals was calculated using the computer program EPIWIN (v4.00), AOPWIN (v1.92). Based on the reaction rate constant k(OH)=14.4562 x 10E-12 cm³/molecule x sec at 25°C and assuming a OH radical concentration of 5 x 10E5 radicals/cm³ (24 -h day) a half-life t1/2of ca. 27 h was calculated. The base-catalysed hydrolysis rate constant of tributyl acetyl citrate was calculated by HYDROWIN program (v 2.00) published by the U.S. Environmental Protection Agency. Tributyl acetyl citrate is in the applicability of the model. The total aqueous base-catalysed rate constant (Kb) at ph > 8 and 25 °C has been calculated to be 5.755 x 10E-2 L/mol x sec. Predicted half-lifes of 3816 y (at pH 4), 3.82 y (at pH 7), 139.4 d (at pH 8) and 13.94 d (at pH 9) indicate moderate to slow hydrolysis of tributyl acety citrate under environmental conditions.

Biodegradation

Biodegradation in water: screening tests

The inherent biodegradation of tributyl acetyl citrate was investigated in a study conducted corresponding to OECD Guideline 302C: "Inherent Biodegradabilty: Modified MITI Test (II)"over a period of 28 days and using activated sludge as inoculum. The biodegradation rate was determined by measurement of oxygen consumption. Inoculum blank and procedural/functional control with the reference substance aniline were performed.The test item proved to be inherently biodegradable under the test conditions employed (82% biodegradation after 28 d). The functional control reached the pass level >60% after 14 d.

The ready biodegradation of tributyl acetyl citrate was investigated in a study conducted according to EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test; 2008) and OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test; 1992) over a period of 28 days and using a mixed inoculum composed of sewage from a sewage treatment plant working predominantly on domestic sewage and soil. The test item proved to be not readily biodegradable under the test conditions employed (16% biodegradation after 28 d). In the toxicity control containing both test and reference item 47%biodegradation based on ThOD occurred within 14 d thus indicating that the test item was not inhibitory at the concentration tested. The inherent biodegradation of tributyl acetyl citrate was investigated in a study conducted corresponding to OECD Guideline 302C: "Inherent Biodegradabilty: Modified MITI Test (II)" over a period of 28 days and using activated sludge as inoculum. The test item proved to be inherently biodegradable under the test conditions employed (82% biodegradation after 28 d).

Biodegradation in soil

From several test results on mineralization in soil and compost, acetyl tributy citrate can be classified as readily biodegradable in these substrates. The reduced degradation in one test with compost could be attributed to deficiencies in the applied method.

Bioaccumulation

No experimental studies on bioaccumulation of tributyl acetylcitrate in aquatic and terrestrial organisms are available.

Therefore the bioconcentration factor BCF of tributyl acetyl citrate was calculated using EPIWIN (v 4.0), BCFBAF (v 3.00). The calculation yielded a BCF=31.57 L/kg wet wt taking into account the measured log Kow of 4.86. Based on the result, a low potential for bioconcentration is to be expected.

Adsorption

The soil sorption coefficient Koc of tributyl acetylcitrate was determined using the HPLC method (OECD 121, EC C.19). The resulting log Koc was 4.271, i.e. Koc = 18664 L/kg. According to the classification scheme of Blume & Ahlsdorf (1993), tributyl acetylcitrate shows a high (log Kow method) to very high sorption onto soil organic matter.

Henry's Law constant

Henry's Law constant of tributyl acetylcitrate was calculated using EPIWIN (v4.0), HENRYWIN (v3.20). The calculation of Henry's Law constant according to the equation H=vp/ws yielded a value of 4.434 Pa x m³/mole using a measured water solubility of 4.49 mg/L and a vapour pressure of 0.000371 mm Hg. Based on the result, tributyl acetylcitrate can be considered to be moderately volatile from aqueous solution.

Distribution modelling

The environmental distribution of tributyl acetylcitrate was calculated according to Mackay Level I (v3.00). The substance is about equally distributed to air (16.1%); water (10.5%), soil (37.9%) and sediment (35.4%); the distribution to the other compartments (fish, aerosol, suspended particles) is negligible.