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Biodegradation in water: screening tests

Description of key information

The biodegradation study was conducted for the substance according to OECD 301B "Ready Biodegradability: CO2 Evolution Test" and GLP. In addition, the probability of biodegradation was estimated for the ten most abundant individual structures of the substance according to the available analytical information. 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:

under test conditions no biodegradation observed

Additional information

Two biodegradation studies were conducted on the substance: OECD 301F "Ready Biodegradability; Manometric Respirometry Test" and OECD 301B "Ready Biodegradability: CO2 Evolution Test". Both studies were done according to GLP. In addition, the probability of biodegradation was estimated for the ten most abundant individual structures of the substance according to the available analytical information. The ES&RC was conducted by using the probability of biodegradation of the hydrocarbon blocks with PETRORISK model (see CSR sections 9&10).

The supporting study (Roulstone P. 2012) for evaluating biodegradation for the UVCB substance in water was conducted according to OECD 301F "Ready Biodegradability; Manometric Respirometry Test" and GLP. The study results was considered as reliable with restrictions, because emulsifier agent used in the test could have had effect on the results and therefore makes the results reliable with restrictions. The study results together with BIOWIN estimates were considered as weight of evidence to evaluate biodegradation of this substance. According to the study, the test substance attained 32 % degradation after 28 days and was therefore not considered as readily biodegradable.

The key study (Muckle M. 2014) was done for the UVCB substance according to OECD 301B "Ready Biodegradability: CO2 Evolution Test". The test fulfills all validity criteria mentioned in OECD 301 B guideline and it was conducted in compliance with GLP. After 28 days biodegradability of the substance was 33 % and therefore the test item cannot be considered as “readily biodegradable”.

The exposure assessment and risk characterisation for the UVCB substance was conducted by using the PETRORISK model. This model uses the information on the biodegradation of the hydrocarbon blocks which have been identified from the substance. Therefore, the biodegradation potential was also estimated with the BIOWIN v4.10 model, which is part of the EPISUITE tool. The probability of biodegradation was estimated for the ten most abundant individual structures of the 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 (5 components), or weeks (4 components).

The key value for CSA was selected based on the result from the OECD 301B biodegradation study conducted for the substance and from the estimated biodegradation of the hydrocarbon blocks of the substance. The substance was considered as not readily biodegradable.

Based on the results of both the studies, the test substance can be concluded as not readily biodegradable in water.