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Biodegradation in water and sediment: simulation tests

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Description of key information

The following study is available for the simulation test (water and sediment) endpoint and are included in support of the argument for the omission of this study:
Adelman D et al (1990) Biogeochemistry of Butyltins in an enclosed Marine Ecosystem, Environ. Sci. Technol. 24, 1027-1032.
The study has been allocated a Klimisch score of 4 and is thus only considered a supporting study for this endpoint.

Key value for chemical safety assessment

Additional information

The study Adelman et al (1991) was assigned a reliability score of 4 (not assignable). The study was provided as supporting information. The study was performed to non-standard methods and GLP status was not reported. Tributyltin (TBT) and its degradation products werestudied by introducing radiolabeled tributyltin into a 13-m3marine enclosure (a MERL mesocosm) with near-natural water column and benthos. TBT and its degradation products were monitored for 278 days. TBT concentrations in the water column (initially 590±20 ng L-1) decreased at a rate of 0.20 day-1for 15 days and then slowed to 0.10 day-1. Most TBT was lost from the water column through biodegradation, which occurred at a rate of 0.08day-1. Two-thirds of the degradation proceeded through debutylation to dibutyltin (DBT), which in turn degraded to monobutyltin (MBT) at ~0.04 day-1. One-third of the TBT was degraded directly to MBT. There was no evidence for degradation of MBT in the water. Another portion of the TBT removed from the water column was transported to sediments. TBT in the sediments did not appear to measurably degrade. A portion of the TBT was apparently transported rapidly to the air-water interface and then was lost from the tank

Results were considered to be indicative of biodegradability in the environment.

In accordance with column 2 of REACH Annex IX, Simulation testing on Ultimate Degradation in Surface Water (required in section 9.2.1.2) does not need to be conducted as the chemical safety assessment concludes that the substance is of no immediate concern to the environment. The available data are adequate for classification and labeling purposes and PBT assessment, so no further testing is required.

In accordance with column 2 of REACH Annex IX, Sediment Simulation testing (required in section 9.2.1.4) does not need to be conducted as the chemical safety assessment concludes that the substance is of no immediate concern to the environment. The available data are adequate for classification and labeling purposes and PBT assessment, so no further testing is required. Also direct and indirect exposure of the sediment is unlikely.

In accordance with column 2 of REACH Annex IX, identification of degradation products (required in section 9.2.3) does not need to be conducted as the chemical safety assessment concludes that the substance is of no immediate concern to the environment. The available data are adequate for classification and labeling purposes and PBT assessment, so no further testing is required. Also direct and indirect exposure of the soil and sediment is unlikely.