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Environmental fate & pathways

Biodegradation in soil

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Description of key information

The recovery of the three UVCB main components directly after application ranged depending on compound and soil between 78.2% and 109.5% and therefore the extraction method was suitable.
Based on the kinetic calculations the following DT50 time ranges were found depending on test soil:
ADSA: 349 – 839 days
AMSA: 56 – 1424 days
HIBA: 5 – 49 days
The main components showed different patterns of concentration decrease. The soil type affected also this decrease. In all soils tested, the two sulfonic components (ADSA and AMSA) disappeared slowly. The concentration decrease of carbonic acid HIBA was clearly faster. A clear correlation between soil parameters and disappearance of the main components was not found.

Key value for chemical safety assessment

Additional information

The test substance is an UVCB substance containing five identified organic substances (see IUCLID section 1.2). The organic part represents about 40% (wet weight) of all the test substance. Due to this diversity of components, it was thus not possible to synthesize a radiolabeled sample which was representative of all the test substance. According to paragraph 6 of OECD Test guideline No. 307, as it was not possible to prepare such radiolabeled sample, the experiment focused on transformation rates, not on transformation pathways. As indicated in the letter sent to ECHA (communication number TPE-D-0000002417-75-05/F) in October the 16th 2013, after discussion with study directors, it had been concluded that the protocol described in OECD Test guideline No. 307 had to be adapted to this specific test substance by focusing on the following major organic components:

- diammonium 2-oxopropane-1,3-disulphonate ((CAS N°25372 -95 -6); 14.5 -18% wet weight; ADSA);

- isobutyrate mixture (10-12% wet weight): 2-hydroxy-2-methylpropanoic acid (CAS N°594 -61 -6; HIBA) and methyl 2 -hydroxy-2 -methylpropanoic acid (CAS N°2110-78-3; HIBM);

- ammonium 2-oxopropane-1-sulfonate (4.5-6% wet weight; AMSA).

 

According to IUCLID section 1.2, these three components represent at least more than 80% of all the organic components. Regarding the other components,the degradation in soil of dimeric form of methacrylic acid (2.5-4% wet weight) is expected to be fast and complete and would be mineralized based on the methacrylic acid (EC N°201-204-4/CAS N°79-41-4) biodegradation data disseminated by ECHA.

The 2-methoxy-2-methylpropanoic acid (CAS N°13836 -62 -9) is present in too low proportions(0.5-2% wet weight)to be quantified in soil.

Therefore, the concentrations of the three major substances (the proportion of HIBM in the test substance was too low to allow detection of this component in soils) were followed in four soils exposed to the test substance for 120 days according to OECD Test guideline No. 307. The test was extended to 147 days in an effort to reach a plateau for some components.The results showed that the recovery of the three main substances directly after application were ranged between 78.2% and 109.5%, depending on substance and soil. Therefore, the extraction method was considered to be suitable.

Quantification of the three main components was accomplished by means of LC-MS/MS.

Based on the kinetic calculations the following DT50 time ranges were found, depending on test soil:

ADSA: 349 – 839 days

HIBA: 5 – 49 days

AMSA: 56 – 1424 days

The main components showed different patterns of concentration decrease. In all soils tested, the two sulfonic components (ADSA and AMSA) disappeared slowly. The concentration decrease of HIBA was clearly faster. A clear correlation between soil parameters and disappearance of the main components was not found.