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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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An OECD 309 study has been performed in response to Final Decision letter DEC-SEV-700-960-7-1-1_DEC which requested that an aerobic mineralisation in surface water – simulation biodegradation test (OECD TG 309) on the constituent 1,1,3-trimethyl-3-phenylindan (CAS 3910-35-8). This is a constituent of this substance and is one of three representatives of the dimer fraction of the UVCB.


The rate of transformation as well as identification of transformation products of [14C]1,1,3-trimethyl-3-phenylindane was determined in a surface water system under aerobic conditions in the laboratory at 12°C (Scymaris, 2022, study number 1027.02803) alongside determination of DT50. The procedures employed were based on the relevant OECD 309 test guidelines (2004) and was conducted in compliance with GLP.


Based on preliminary work, the test design was amended to a closed bottle method which excluded 14CO2 and volatile organic compound traps on all test vessels, except the positive and solvent control test vessels which had 14CO2 traps only. The sampling procedure was also informed by the preliminary work.


The surface water systems were acclimated under test conditions overnight, after which the exposure test vessels were treated with concentrated stocks of [14C]1,1,3-trimethyl-3-phenylindane to give final nominal concentrations of 1 µg/L and 10 µg/L in the water phase. The test vessels were incubated in the dark at 12 ± 2°C for up to 60 days after treatment. At appropriate time intervals (days 0, 7, 14, 28, 42 and 60), duplicate test vessels of each concentration were sampled for analysis.


This study showed that [14C]1,1,3-trimethyl-3-phenylindane did remain in the water at 12°C; the majority of the applied radioactivity was present in the water with >86% AR recovered in the water at all timepoints.≤5% of the applied radioactivity was present in the vessel rinses throughout the study. Radio-HPLC analysis of the water on day 60 showed a mean 90.1% of the applied radioactivity in the 1µg/L vessels and a mean 75.9% of the applied radioactivity in the 10µg/L vessels was present as [14C]1,1,3-trimethyl-3-phenylindane.


Mineralisation (measured as evolved14CO2) accounted for up to 11.2% and 9.1% of the applied radioactivity in the 1µg/L and 10µg/L vessels (as dissolved14CO2), respectively. One transformation product was observed triggering the metabolite identification criteria and the structure based on LC-MS/MS was proposed with a molecular weightof 266.33 g/mol, suggesting this metabolite is the carboxylated form of 1,1,3-trimethyl-3-phenylindane, namely 1,3-dimethyl-3-phenyl-2,3-dihydro-1H-indene-1-carboxylic acid. Therefore 1,1,3-trimethyl-3-phenylindane showed the potential to degrade.


Using single first order kinetic analysis on the water the DT50for the test item was calculated as 542 and 205 days for the 1µg/L and 10µg/L vessels, respectively.

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