Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Note:

The main constituent Structure A (CAS 597 -82 -0) is currently under evaluation as part of the Community Rolling Action Plan 2016 (Member State: The Netherlands). Studies are ongoing.

Stability

Hydrolysis

Whole substance

No significant hydrolysis could be observed in the hydrolysis study with the uvcb substance (Ciba 1998).

 

Structure A

However, a hydrolysis study based on OECD 111 was performed to examine the hydrolysis behaviour of one of the main constituents (Structure A, CAS 597-82-0) and the assumed transformation products (Ciba specialty Chemicals Inc, 2007). After up to 30 days of incubation, the half-life of the parent compound (O,O,O-triphenyl thiophosphate) was determined to be 24.2 days (pH 9), 102.4 days (pH 7) and 115.8 days (pH 4) at 25°C. After up to 30 days of incubation, the half-life of the expected transformation product (triphenyl phosphate) was determined to be 1.7 days (pH 9), 10.9 days (pH 7) and 77.9 days (pH 4) at 25°C.

In addition, formation of phenol, which is generated during the hydrolysis process of the parent compound and the transformation product, was investigated. The increasing Phenol concentrations show that both O,O,O-triphenyl thiophosphate and triphenyl phosphate are further hydrolysed under separation of phenol.

However, it can be expected that the abiotic transformation in water of O,O,O-triphenyl thiophosphate to triphenyl phosphate takes place to a minor extent as the hydrolysis half lives of the triphenyl phosphate are much lower than the half-lives of triphenyl thiophosphate. Furthermore, data on triphenyl phosphate show a difference in the ecotoxicity profile and in the environmental behaviour. Triphenyl phosphate is readily biodegradable and shows acute and chronic effects in toxicity studies to aquatic organisms leading to a classification as Aquatic Acute 1 (M-Factor 1)and Aquatic Chronic 2 according to Regulation (EC) No 1272/2008 (CLP/GHS)(ECHA disseminated data on CAS 115-86-6, January 25, 2016). As O,O,O triphenyl thiophosphate does not fulfill the criteria for ready biodegradability and shows no toxic effects to aquatic organisms up to the solubility limit it can be assumed that the transformation to triphenyl phosphate takes place to a minor extent in aquatic media.   

 

Stability during Use

During use as lubricant additive one of the main constituents (Structure A CAS 597-82-0 Triphenyl thiophosphate) degrades to triphenyl phosphate which forms a multilayered solid film on the metal or metal oxide which will be further degraded. In a tribotesting study at 423K with poly-α olefin (PAO) it could be shown that the reaction products are pyrophosphate, organo-phosphate and sulfate species. This degradation is metal catalysed. Oxygenated compounds produced by the oxidation of the base oil adsorbed onto the iron surface and reacted with it to form carbonates and carboxylates (Mangolini F., Rossi A., Spencer N.D.Tribochemistry of Triphenyl Phosphorothionate (TPPT) by In Situ Attentuated Total Reflection (ATR/FT-IR) Tribometry, The Journal of Physical Chemistry 2012,116,5614-5627 /Mangolini, F.; Rossi, A.; Spencer, N.D. Influence of metallic and oxidized iron/steel on the reactivity of triphenyl phosphorothionate in oil solution.Tribol. Int.2011,44, 670–683., /David W. Johnson and John E. Hils. "Phosphate Esters, Thiophosphate Esters and Metal Thiophosphates as Lubricant Additives"LubricantsVol. 1 Iss. 4)

The same mechanism is assumed for the butylated constituents.

 

Biodegradation

Whole substance

The uvcb substance was found to be poorly biodegradable in a Closed bottle test according to OECD 301D (Huntington 1996).

 

Structure A

Data on a major constituent are available (structure A):

The ready biodegradability of the test item was assessed over a 28 day period by the modified Sturm test (OECD 301B). The nominal test concentration was 0.26 µg a.s./L (two replicates), which was in the range of the water solubility of the test substance. CO2 measurements showed up to 17.8 and 19.3% mineralisation after 29 days. Further investigations during experimental phase using radiolabelled test item showed that only 51.5% and 60.8% of the radioactivity consisted of the test item, whereas the remaining radioactivity consisted of its degradation products. Thus, the test item is not completely biodegraded over a 28 day period under the test conditions but up to 19% is mineralized and additionally up to 48.5% of the test item is transformed into its transformation and degradation products. Phenol, can be identified from the chromatogram of the degradation products. This is supported by the results of the hydrolysis study, which showed that different transformation products of the test substances are generated in parallel once hydrolysis has started.

The results indicate that the test item cannot be classified readily biodegradable but well primarily degradable under conditions of the test.

The inherent biodegradability of the radiolabelled test item (Structure A) was assessed over a 28 day period by the MITI-test (II) according to OECD 302C. The nominal test concentration was 0.26 µg a.s./L, which was in the range of the water solubility of the test substance. The test material attained up to 59.5 and 66.8 % biodegradation after 28 days.

These results indicate that the test item can be classified as inherently biodegradable under conditions of the test.

 

Overall degradation and persistence

In conclusion, tests on the entire uvcb substance did not reveal a relevant biodegradation or hydrolysis rate of the compound. The very low solubility of the substance (or its single constituents) may have reduced the availability and hence the degradability of the substance in the test. However, for one of the main components (CAS 597-82 -9) additional experimental data is available which revealed that this component is inherently biodegradable and primarily biodegradable under formation of the rapidly degradable degradation product phenol.

The substance will hydrolyse in water. Furthermore, the identified transformation products from the hydrolysis and biodegradation studies are not persistent and subject to further degradation (e.g. phenol is readily biodegradable (ECHA disseminated dossier CAS 108 -95 -2, accessed 2016-02-02)).

During use as additives in lubricants the thiophenyl phosphates and alkylated thiophenylphosphates are assumed to degrade to the respective phosphates adsorb to the metal surface and will be further degraded.

 

This clearly shows that Structure A is not very persistent. According to the Regulation (EC) No 1907/2006,Annex III, paragraph 1.1.1 and 1.2.1 the test item does not fulfill the criterion for persistent or very persistent substances.

However, for the butylated constituents of the uvcb substance similar mechanisms are assumed but no experimental data are available.

 

Bioaccumulation

In a weight of evidence approach using experimental data on the whole substance and QSAR on the different constituents the bioaccumulation potential of the constituents was assessed. STRUCTURE A was identified as bioaccumulative (BCF > 2000). The other butylated constituents have a lower bioaccumulation potential in the experimental study supported by QSAR. Supported by the Diammax Average it can be concluded that constituents B to I are not bioaccumulative (BCF < 2000)

Transport and Distribution

Based upon measured data and calculations adsorption to the solid phase is expected for the constituents. The adsorption potential increases with increasing butylation.