Petroleum gas oil fraction, co-processed with renewable hydrocarbons of plant and/or animal origin

Endpoint summary

Additional information

General discussion of environmental fate and pathways:

When complex petroleum substances are released into the environment, the hydrocarbon constituents distribute to the different environmental compartments according to individual physico-chemical properties (e.g. volatility, water solubility, partition coefficients). Exposure concentrations are further modulated by differential degradation rates between constituents and compartments. This makes it difficult to assess environmental exposure of petroleum substances from field monitoring studies because measured concentrations of constituents or total hydrocarbons detected in the environment can no longer be directly related to the original petroleum substance. A further complication is multiple hydrocarbon sources, both man-made and natural, which may contribute to concentrations observed in each environmental compartment (CONCAWE, 1999). Therefore, it is not possible to directly apply current risk assessment guidance, originally developed for simple substances, to complex petroleum substances.

To quantify environmental exposure resulting from multimedia distribution and degradation of hydrocarbon components that comprise a complex petroleum substance the ‘Hydrocarbon Block Method’, has been proposed by CONCAWE (1996) and EC (2003) and subsequently implemented in REACH (ECHA, 2008). In this approach, individual hydrocarbons with different partitioning and degradation properties are used to simulate petroleum substance fate in the environment.

Degradation in the environment is a result of abiotic processes and biodegradation. The relative importance of these processes will depend upon the environmental compartment to which the individual components of the petroleum product partition. In general, abiotic processes are important in the atmosphere, whilst biodegradation is the principle mechanism of the breakdown of lower carbon chain length products in water and soil. Direct photolysis is not expected to be a major degradation pathway for many of the hydrocarbon components in petroleum substances and neither is hydrolysis, as the components of petroleum products lack hydrolysable functional groups.

The combined role of partitioning and degradation properties of constituent hydrocarbons on environmental fate and resulting exposure of complex petroleum substances at both local and regional scales has been predicted using the PETRORISK model (https://www.concawe.eu/reach/petrotox) based on the principles of the hydrocarbon block method.

 

Hydrolysis:

Hydrolysis is a reaction in which a water molecule or hydroxide ion substitutes for another atom or group of atoms present in a chemical resulting in a structural change of that chemical. Potentially hydrolyzable groups include alkyl halides, amides, carbamates, carboxylic acid esters and lactones, epoxides, phosphate esters, and sulfonic acid esters (Neely and Blau, 1985). The lack of a suitable leaving group renders compounds resistant to hydrolysis.

The chemical constituents of diesel/gas oil fractions consist entirely of carbon and hydrogen and do not contain hydrolyzable groups. As such, they have a very low potential to hydrolyze. Therefore, this degradation process will not contribute to their removal from the environment.

Further testing is not required under Annex XI, section 1.2.

 

Biodegradation:

The ready biodegradability study, 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.

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.

 

Biodegradation in water and sediment, simulation test:

Substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint is characterized using quantitative structure property relationships for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of this substance with the PETRORISK model (see Product Library in PETRORISK report attached in IUCLID section 13).

 

Biodegradation in soil:

Substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint is characterized using quantitative structure property relationships for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of this substance with the PETRORISK model (see Product Library in PETRORISK report attached to IUCLID Section 13).

 

Aquatic/sediment bioaccumulation:

Substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint has been calculated for representative hydrocarbon structures using the BCFWIN as input to the hydrocarbon block method incorporated into the PETRORISK model. The predicted BCFs for hydrocarbons are generally overly conservative since biotransformation is not quantitatively taken into account. Therefore, predicted indirect exposure and resulting risk estimates are likely to be overestimated.

 

Terrestrial bioaccumulation:

Substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint has been calculated for representative hydrocarbon structures using default algorithms in the EUSES model as input to the hydrocarbon block method incorporated into the PETRORISK model. The predicted BCFs for hydrocarbons are generally overly conservative since biotransformation is not quantitatively taken into account. Therefore, predicted indirect exposure and resulting risk estimates are likely to be overestimated.

 

Adsorption/desorption:

Substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint is characterized for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of this substance with the PETRORISK model (see library in PETRORISK report attached in IUCLID section 13).