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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The biodegradation study (OECD 301F) conducted for the read-across substance showed that the substance is readily biodegradable. In addition, the probability of the biodegradation was estimated for the ten most abundant individual structures of the substance according to the available analytical information. Nine substances were estimated to be readily biodegradable. The ES&RC was conducted by using the probability of biodegradation of the hydrocarbon blocks with PETRORISK model (see CSR sections 9&10).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The key study for evaluating biodegradation for the UVCB substance in water was based on read-across substance (High naphtenic, heavy, straight-run naphtha) (American Petroleum Institute, 2008). The test was conducted according to OECD 301F "Ready Biodegradability; Manometric Respirometry Test" and in compliance with GLP. The study result shows that the substance can be regarded as readily biodegradable (biodegradation 77 % over 28 day testing period).

The target UVCB substance was tested twice using the OECD 301F test (Roulstone, P. 2012 and Tothova, E. 2013). Due to a obvious problems with sampling and sample handling highly volatile components might have evaporated prior testing. Furthermore, an emulsifier agent used in the test by Roulstone, P. (2012) could have had effect on the results. Thus the results of these studies were considered not reliable and these studies are indicated as supporting studies only. In the test conducted by Tothova, E. (2013) the test period was extended to 42 days due to a low biodegradation. The biodegradability of the test substance was 8.05 % both at 28 days and at 42 days. The other biodgadation test by Roulstone P. (2012) was considered not reliable, because emulsifier agent used in the test could have had effect on the results. After 14 days the biodegradability of test substance was 0 % and after 28 days 0%. The study results by Tothova, E. (2013) and Roulstone, P. (2012) would mean that the test substance didn’t meet a criterion for ready biodegrability by OECD 301F Ready Biodegrability Manometric Respirometry test (60 % of ThOD).

To further support the conclusion that the target UVCB substance is readily biodegradable estimation with the BIOWIN v4.10 model was conducted. The probability of the biodegradation was estimated for the ten most abundant individual structures (based on mass-%) of the target UVCB substance according to the available analytical information. BIOWIN estimates the probability biodegradation of an organic compound in the presence of mixed populations of environmental microorganisms. Of the ten most abundant individual structures, nine were estimated to be readily biodegradable, and the time required for ultimate degradation for these components were estimated to be days to weeks, or months.

Based on the results of the studies, the test substance can be concluded as readily biodegradable in water.