Registration Dossier
Registration Dossier
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EC number: 807-747-9 | CAS number: 144429-84-5
Endpoint summary
Administrative data
Description of key information
Additional information
Assessment of the parent compound (source and target)
Degradation:
The substance is not readily biodegradable as established in an OECD 301F test (2018) and 301B (1989) .
The degradation in an aerobic sediment/water system was tested according to OECD-guideline no. 308 (CIBA 2006, RCC study no. A10653), revealing that the test item disappears rapidly mainly by microbial hydrolysis to Metilox acid (CAS: 20170-32-5). Metilox acid is then further eliminated mainly by adsorption to sediment (non-extractable residues) and degradation to several minor metabolites. OASIS results and the findings in the bioconcentration study support this transformation pathway. Therefore, it can be expected that degradation will be higher in absence of sediment.
Bioaccumulation:
In an OECD 305 flow through test on Rainbow trout, a low bioaccumulation potential of the substance was established with a maximum BCF (whole fish) of 260.
Transport and distribution:
The substance exhibits a high potential for adsorption and negligible volatilization. Soil and sediment are expected to be the main target compartments for this substance.
Supporting assessment of the major degradation product Metilox acid (CAS: 20170-32-5)
Degradation
Metilox acid is not readily biodegradable in the Modified Sturm test with 3-7% degradation at 10.3 and 20.3 mg/L.
Based on the results of the degradation study according to OECD 308 it could be expected that Metilox acid will either be further transformed or bound to the sediment as it disappears from the water phase and sediment (extractable part) of the river and pond systems.
The rate of transformation or ultimate degradation under environmental conditions are not yet known.
Bioaccumulation
The bioconcentration of Metilox acid was tested in a study on the uvcb substance. One constituent of this substance is Metilox (CAS 6386 -38 -5) and metilox acid was identified as relevant transformation product.
The study was conducted according to OECD guideline 305 C. At 50 µg/L, the bioconcentration factor was determined to be 60-223 and 121-532 at 5 µg/L, respectively, after 8 weeks of exposure. The exposure concentration is well below the solubility limit of Metilox acid in water.
The BCF values are clearly below 2000.
Furthermore, the PBT Expert Working Group of the Technical Committee of New and Existing Chemicals has agreed that Metilox should be deleted from the list of potential PBT / vPvB substances (see attachment IUCLID chapter 13).
Transport and distribution
In aquatox tests solubilities up to 100 mg/L could be achieved (Elendt M4 Medium, short term toxicity test on Daphnia, 2011). Therefore, the substance is expected to end up in the soil and to a lesser degree in the water. Based on the results of the degradation study according to OECD 308 it could be expected that Metilox acid will either be further transformed or bound to the sediment as it disappears from the water phase and sediment (extractable) of the river and pond systems.
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