Registration Dossier
Registration Dossier
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EC number: 227-572-6 | CAS number: 5892-47-7
Endpoint summary
Administrative data
Description of key information
Additional information
PHOTODEGRADATION
DIRECT PHOTODEGRADTION
The registration substance does absorb light >290 nm. Direct photolysis can therefore occur under environmental conditions.
INDIRECT PHOTODEGRATION
The registration substance can react with OH radicals rapidly (primary degradation). Also reactions with other sensitizers in soil and water (DOM, Chinons, huminic acids,...) are possible.
The calculated half-live in air is 0.36d. Due to the low vapour pressure this might be of low relevance, but indirect photodegradation in water and soil is likely.
HYDROLYSIS
The registration substance contains no functional groups which can be associated with hydrolysis.
BIODEGRADATION SCREENING TEST
The feasibility of biodegradation was investigated in a preliminary test and further examined by different ways of application.
The preliminary study was performed with a mixed inoculum of non-adapted soil and non-adapted activated sludge in the Manometric Respirometry Test for a period of 28 days.
There have been experiments to improve the bioavailability by the use of silica gel, silicon oil or soil. In part due to separation from the carrier material, in part due to the practical properties of the test item this was not successful. Therefore, it was concluded that no improvement of the bioavailability could be achieved.
Due to the low solubility and thus bioavailability of the test item under the conditions of the OECD 301 tests further studies for ready biodegradability are not feasible.
In a second study the registration substance has been investigated in an guideline comparable study (79/831/EWG (part C) ; DIN 38 409, part 52) to be not readily biodegradable.
BIODEGRADATION IN SOIL
The biotransformation of [ring-UL-14C]2,4,6-tri-sec-butyl-phenol was studied in three different soils, i.e. silt loam (Hoefchen am Hohenseh, organic carbon 2.3%, pH 6.3, ID: HaH, Burscheid, Germany, sandy loam (Wurmwiese, organic carbon 2.0%, pH 5.3, ID: WuW, Monheim, Germany), and clay loam (Dollendorf II, organic carbon 4.4%, pH 7.2, ID: Doll, Blankenheim, Germany) for 60 days under aerobic conditions in the dark at 20 °C and about 55% WHCmax (max. water holding capacity).
The material balance for the biological active samples was in the range of 97.0%- 102.5% (HaH), 97.8%-101.2% (WuW) and 97.7%-103.5% of AR (Doll) for the test systems indicating that no radioactivity was lost during the course of the study (mean values of duplicates).
The parent compound decreased from 91.4%, 85.6% and 93.9% of the applied amount at DAT-0 to 3.1%, 3.3% and 4.1% of the applied radioactivity at the end of the study, respectively.
The half-lives of 2,4,6-tri-sec-butyl-phenol were calculated according to single first order (SFO) as 9.9, 8.4, and 8.9 days (mean 9.1 days) for soil HaH, WuW and Doll, respectively.
The main step in the degradation was formation of non-extractable residues followed by emerging of carbon dioxide.
Due to the exhaustive cold and hot extraction the portions of non-extracted residues at DAT-0 were low (8.6%, 10.5%, and 7.5% in soils HaH, WuW and Doll), and increased to 60.6% (DAT-60), 46.8% (DAT-60) and 61.2% (DAT-60).
Extractable 14C-residues decreased from 93.9%, 90.7% and 96.1% of the applied amount at DAT-0 to 15.6%, 17.8% and 15.5% of the applied RA at the end of the study, respectively.
The amount of formed 14CO2 increased steadily during the entire study period. At the end of the study, 60 days after application, evolved 14CO2 was 23.0%, 34.6% and 23.0% of the applied RA in soils HaH, WuW and Doll, respectively.
Major Outcome of Study
The data gathered in the current laboratory investigation demonstrated, that the test item 2,4,6-tri-sec-butyl-phenol had well degraded in all 3 soils with a DT50 of 8.4 to 9.9 days (20 °C) according to a single first order kinetics (SFO)
The formation of bound residues is the major degradation step. Metabolites were detected in low amounts only. At the end of incubation, the formation of 14C carbon dioxide was the main degradation path. The amount increased to 23.0% - 34.6% indicating the complete mineralization of the test compound and bound residues.
Significance of Results to Environmental Behavior of Test Compound
The test item 2,4,6-tri-sec-butyl-phenol degraded fast in soil under aerobic conditions. The high amount of 14CO2 indicates the complete mineralization.
The formation of radioactive carbon dioxide was high in all soils, reaching levels of 57.5%, 58.8% and 54.8% of the applied radioactivity in soils I to III, respectively, after 62 days of incubation
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