Registration Dossier
Registration Dossier
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EC number: 249-854-8 | CAS number: 29797-40-8
Endpoint summary
Administrative data
Description of key information
Additional information
Ready biodegradability:
No degradation (0 %) of DCT mixture was found in a 28-d manometric respirometry test according to the OECD 301F, showing that DCT mixture is not readily biodegradable (Reference: Caspers & Müller, 1991).
Biodegradation in soil:
A microcosms study in soil slurry under anaerobic, methanogenic test conditions (Reference: Ramanand, 1993) provided the following results:
- DT50 of ca. 90 days for the three main isomers 2,4-DCT, 2,5-DCT and 3,4-DCT. Transformation products were 4-CT, 3-CT and 2-CT as well as toluene.
- Slower degradation was found for 2,3 -DCT and 2,6-DCT (according to the authors "not susceptible to the microorganisms"). Reading from the graphs, 2,3 -DCT and 2,6 -DCT declined by about 40% within 120 to 150 days.
The concentrations at which the DCT isomers were tested (121, 129 or 161 mg/L) are about 10 times higher than the LC50 determined for 3,4 -DCT in the "toxicity to microorganisms test" by Schultz, 1999. Therefore, it must be assumed that the test concentrations negatively influenced the metabolisation of the DCT isomers in soil slurry.
Biodegradation in water and sediment:
A simulation test in surface water according to OECD 309 showed a half-live of 31.7 days at 12°C for the whole mixture of isomers. The four main isomers have half-lives of 25 to 35 days. However, there is one isomer (2,3 -DCT, content about 9%) which has a half life of 55 days at 12°C. The latter result is explained by a metabolism test which showed that all dichlorotoluenes will be degraded by hydroxylation of the methyl group. Most isomers (but not 2,3 -DCT) are additionally degraded by hydroxylation of the aromatic ring.
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