Registration Dossier
Registration Dossier
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EC number: 295-405-4 | CAS number: 92045-23-3 A complex combination of hydrocarbons produced by the distillation of the products of a steam cracking process. It consists predominantly of hydrocarbons having a carbon number of C4, predominantly 1-butene and 2-butene, containing also butane and isobutene and boiling in the range of approximately minus 12°C to 5°C (10.4°F to 41°F).
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
The members of category C4, high 1,3 -butadiene (>0.1%) are considered not to be readily biodegradable as there is insufficient data to confirm ready biodegradability.
Key value for chemical safety assessment
- Biodegradation in water:
- under test conditions no biodegradation observed
Additional information
As the members of category C4, high 1,3 -butadiene (>=0.1%) are gases at standard temperature and pressure, conducting a standard ready biodegradability test is technically difficult and, based on exposure estimates, the test may not be relevant.
Measured data are available for 1,3-butadiene. An OECD TG 301D closed bottle test (MITI, 2001) on 1,3-butadiene reported 0 - 4% biodegradation over 28 days. We have been unable to obtain a copy of the original report in order to assess its reliability.
As the member streams within this Category are gases at standard temperature and pressure, conducting a standard ready biodegradability test is technically difficult and based on exposure estimates the test may not be relevant. Therefore, it is considered appropriate to predict the biodegradability of a number of C4 substances (butane, isobutane, but-1 -ene, isobutene and 1,3 -butadiene) using a (Q)SAR model to fulfil this endpoint requirement.
The results of the BIOWIN QSAR model indicated that But-1-ene, Isobutene, Butane and 1,3-butadiene are all readily biodegradable. Isobutane was deemed not readily biodegradable due to having a Biowin 5 (MITI Linear model) of 0.4898 and Biowin 7 (anaerobic linear) of 0.4315. However Biowin 2 (non-linear model), Biowin 3 (ultimate biodegradation time) and Biowin 6 (MITI non-linear model) were all above the screening criteria for Persistence in the PBT Assessment.
The results from the BioHCwin model predict half-lives of between 1.9 and 3.5 days indicating the streams in this category would not be expected to be persistent. The use of BioHCwin is appropriate for this category as these compounds fall within the applicability domains of this model.
Taking into account the measured data for 1,3-butadiene and the (Q)SAR results, there is insufficient evidence to demonstrate that the streams in this category are readily biodegradable.
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