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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Abiotic degradation; Hydrolysis

The test item is a complex mixture for which the test guidelines for hydrolysis are not recommended because components could have different hydrolytic rates that give rise to non-pseudo first order hydrolysis plots. In addition, hydrolysis products can be analytically indistinguishable from the starting components because larger components hydrolyse to hydrolysis products that have the same structure as components already within the test item. The main functional groups within the components of the test item were carboxylic acids and esters. Carboxylic acids will be hydrolytically stable at environmentally relevant temperatures and pHs. Esters usually hydrolyse at environmentally relevant temperatures and pHs.

Biodegradation

The test item attained 17 % biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline 301B.

Adsorption / desorption coefficient (Koc)

The determination of the adsorption coefficient was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 and OECD TG 121.

 

The test utilized a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moeties was used.

 

It was known that the test item was a complex mixture (UVCB). Some of those components contained a carboxylic acid group with an estimated pKa of 4.2. During method development, it was noted that the group of peaks eluting isocratically were inconsistent in retention time and peak profile. This was considered to be partially due to the carboxylic acid group. Using a mobile phase at approximately pH 3 gave improved peak consistency and profile. The test was therefore performed with acidic and neutral mobile phases.

 

As the pKa was 4.2, the ideal mobile phase pH would be two units lower to give pH 2.2. This was considered too low for the purposes of the test as it was outside the environmentally relevant pH range as few soils would have a pH this low. Consequently, it was decided to adjust the mobile phase to approximately one pH unit below the pKa; this was still outside the limits stipulated by the test guidelines, but some acidic soils are around this pH.

The adsorption coefficient of the test item has been determined as follows:

 

pH 3.4: Koc = 3820 and > 427000; Log Koc = 3.58 and > 5.63

pH 6.5: Koc = 239, 647 and > 427000; Log Koc = 2.38, 2.81 and > 5.63

 

The results suggested that a greater amount of the test item would retain on to soil in acidic conditions while lesser retained components would have a higher retention in acidic conditions compared to neutral conditions. There appears to be a lower percentage of highly retained components in neutral conditions and correspondingly a higher percentage of slightly retained components.

Bioaccumulation

The test item is a complex UVCB for which Log Kow was determined using the HPLC method (OECD 117 and EU Method A.8) with a weighted value being reported as 4.65. However, the mean Log Kow for two out of three samples was less than 4.5 indicating that uptake of the organic components of the test item is unlikely and that the aquatic BCF will be below the 2000 L/kg threshold where bioaccumulation becomes a concern (see ECHA Guidance on Information requirements and chemical safety assessment Chapter R11: PBT assessment (Version 2.0; November 2014). Further evidence for low bioaccumulation potential is provided by the most abundant UVCB component (25 %) where EPISuite BCFBAF v3.01predicts BCF as 3.16 L/kg wet weight based on SMILES for the component even though Log Kow for the same component is estimated as 4.85. As a result, bioaccumulation of the UVCB test item is not expected to occur as the result of exposure to substance or its constituents and, in accordance with REACH Annex IX, section 9.3.2, column 2, experimental investigation is unnecessary because the substance has a low potential for bioaccumulation.