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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The members of  category C4, high 1,3 -butadiene (>0.1%) are not considered to be readily biodegradable as there is not sufficient data to indicate that they are readily biodegradable.

Key value for chemical safety assessment

Additional information

The members of category C4, high 1,3 -butadiene (>0.1%) are gases at standard temperature and pressure and therefore conducting a standard ready biodegradability test is technically difficult, and based on exposure estimates the test may not be relevant.

Measured data is 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.

In the absence of a standard study, it is appropriate to predict the biodegradability of a number of C4 substances (butane, 2-butene and 1,3-butadiene) using a (Q)SAR model . The data generated can be used as part of a weight of evidence approach to fulfil this endpoint requirement. The use of BioHCwin is appropriate for as these compounds fall within the applicability domains of this model. Results from (Q)SAR models are generally used to confirm persistence, rather than to indicate ready biodegradation. The results from the BioHCwin model do not indicate that the streams in this category would be expected to be persistent.

Taking into account the measured data for 1,3-butadiene and the (Q)SAR available, there is not sufficient evidence to demonstrate that the streams in this category are readily biodegradable.