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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The ready biodegradability of the test item Petroleum gas oil fraction, co-processed with renewable hydrocarbons of plant and/or animal origin (EC 941-364-9) was determined with non-adapted activated sludge in the Manometric Respirometry Test for a period of 28 days. The study was conducted according to OECD guideline 301F and in compliance with GLP.

The test item concentration selected as appropriate was 17.5 mg/L, corresponding to a ThOD of 50.5 mg O2/L per test vessel. The test item was once applied via a stock solution in silicone oil and second without silicone oil.

The 1st and 2nd test item replicate without silicone oil reached the 10 % level (beginning of biodegradation) within 3 days. The 60% threshold was not reached within 28 days. The mean biodegradation on day 28 was 39% in the test item replicates without silicone oil. The 1st and 2nd test item replicate with silicone oil reached the 10 % level (beginning of biodegradation) on day 3. The 60% threshold was reached within 19 days. The mean biodegradation on day 28 was 69% in the test item replicates with silicone oil.

After a test period of 28 days, the test item was not readily biodegradable within the 28-day period of the study without silicone oil. After a test period of 28 days, the test item was readily biodegradable within the 28-day period of the study with silicone oil.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Diesel / gas oil fractions are not readily biodegradable but are considered inherently biodegradable. In a report on environmental classification (Concawe 2001), it was concluded that, based on the known properties of hydrocarbons in the range C9 to C26,diesel/gas oil fractions are not readily biodegradable, but are regarded as being inherently biodegradable, since they can be degraded by micro-organisms.

In a further investigation (Concawe 2012) on PBT evaluation of petroleum substances CONCAWE developed QSAR estimates (BioHCwin) and reviewed existing data for individual hydrocarbons representative of the various ‘hydrocarbon blocks’ covering a range of petroleum substances. Using the Hydrocarbon Block method and data on biodegradation of representative hydrocarbons in the range C9 to C26, it is concluded that diesel / gas oil fractions do not meet the persistence criteria and can be regarded as being inherently biodegradable.

Concawe 2001:Environmental classification of petroleum substances - summary data and rational. Report No 01/54. Concawe Brussels.

Concawe 2012:An evaluation of the Persistence, Bioaccumulation and Toxicity of Petroleum Hydrocarbons (revised), May 2012