Naphtha (petroleum), steam-cracked middle arom.

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

Episuite and the BioHCWin models are well documented and commonly used QSARs for predicting the biodegradation potential of chemicals. Constituents within LOA streams with no heteroatoms (those atoms other than carbon or hydrogen) fall within the applicability domain of these models and they have been recommended by ECHA in the Information Requirement Guidelines.

Reason / purpose for cross-reference:

assessment report

Reason / purpose for cross-reference:

(Q)SAR model reporting (QMRF)

Principles of method if other than guideline:

BioHCwin v1.01 in EPISuite 4.1 (2017). The BioHCwin program was developed specifically for the biodegradation half-life prediction of petroleum hydrocarbons. Primary biodegradation half-lives for individual petroleum hydrocarbons are estimated using multiple linear regression against distinct molecular fragments, using a similar approach to several other biodegradation models such as those within the Biodegradation Probability Program (BIOWIN).

BioHCWin training sets were created using experimental biodegradation data for compounds found in crude oil and its products, with biodegradation references obtained for each of these compounds, mainly from the BIOLOG and DATALOG files of EFDB, TOXLINE and American Chemical Society Chemical Abstracts as well as literature searches. A single recommended biodegradation half-life was chosen for use in the regression analysis from the primary biodegradation data that were compiled for each hydrocarbon structure. Biodegradation data for the xylene isomers and several PAHs were taken from the Syracuse Research Corporation database.

GLP compliance:

no

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
Not applicable

Oxygen conditions:

aerobic

Based on:

other: QSAR calculation

Parameter followed for biodegradation estimation:

other: QSAR calculation

Details on study design:

Not applicable

DT50:

>= 1.46 - <= 63.13 d

Type:

not specified

Remarks on result:

other: Result from QSAR prediction. Range based on the measured constituents in the streams.

Transformation products:

not measured

Remarks:

QSAR Calculation

Details on transformation products:

All 240 parent constituents were evaluated using the Catalogic model to evaluate metabolite persistence. There were 2374 unique metabolites identified from the modelling. Of the unique metabolites, 514 were considered to be readily biodegradable and 1860 not readily biodegradable. However, the primary half-lives indicate that 2315 of the 2374 unique metabolites have a range of half-lives from less than one day to 28 days and 31 metabolites had half-lives ranging from 1 month to 9 months and 15 days. The remaining 28 metabolites had half-lives of over one year. One metabolite had a half-life of 1-month and 27 and a log Kow of 4.54. However, none of the metabolites with half-lives of over one year had log Kow of greater than or equal to 4.5 and are therefore not considered to be bioaccumulative. (see attached Metabolite Persistence Evaluation Report)

Details on results:

Of the 240 constituents, 4 have a half-life of greater than 40 days. Details of the constituents and how their BioHCwin half-lives relate to their persistence assessment are found in the PBT report attached to Section 13 (see cross reference).

Validity criteria fulfilled:

not applicable

Conclusions:

The predicted BioHCwin half-lives of measured constituents of this category range from 1.46 to 63.13 days. Of the 240 constituents, 4 have a half-life of greater than 40 days. Details of the constituents and how their BioHCwin half-lives relate to their persistence assessment are found in the PBT report attached to Section 13 (see cross reference).

Executive summary:

The half-lives of measured constituents (at equal or above 0.1% w/w) of this category have been predicted using the EPISUITE v4.11 BioHCwin model (2017), which uses methodology described by Howard et al. (2005). The predicted BioHCwin half-lives range from 1.46 to 63.13 days. Of the 240 constituents, 4 have a half-life of greater than 40 days.

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

This endpoint is adapted in accordance with REACH Annex XI, Section 1.3 (QSAR). The constituents in the category have a low potential for adsorption to sediments. This indicates that the surface water (measured or predicted) biodegradation rates would be applicable to sediment. An evaluation extrapolation factor of 4 was implemented to the water half-lives to calculate sediment half-lives for screening purposes, according to Boethling et. al (1995). Measured freshwater biodegradation rates were obtained from the Concawe Report (2019), which provides water experimental primary biodegradation half-lives for petroleum substances from reliable sources, including peer-reviewed studies. BioHCWin model biodegradation rates were used for constituents for which no experimental data was available. The BioHCwin model is a well documented and commonly used QSARs for predicting the biodegradation potential of hydrocarbon chemicals. Constituents within LOA streams with no heteroatoms (those atoms other than carbon or hydrogen) fall within the applicability domain of this model and it has been recommended by ECHA in the Information Requirement Guidelines.

Reason / purpose for cross-reference:

assessment report

Reason / purpose for cross-reference:

(Q)SAR model reporting (QMRF)

Principles of method if other than guideline:

An evaluation extrapolation factor of 4 was implemented to the water half-lives to calculate sediment half-lives for screening purposes, acording to Boethling et. al (1995). Measured freshwater biodegradation rates were obtained from the Concawe Report (2019), which provides water experimental primary biodegradation half-lives for petroleum substances from reliable sources, including peer-reviewed studies. BioHCWin model v1.01 (EPISuite 4.1, 2017) freshwater biodegradation rates were used for constituents for which no experimental freshwater half-life was available. The BioHCwin program was developed specifically for the biodegradation half-life prediction of petroleum hydrocarbons. Primary biodegradation half-lives for individual petroleum hydrocarbons are estimated using multiple linear regression against distinct molecular fragments, using a similar approach to several other biodegradation models such as those within the Biodegradation Probability Program (BIOWIN). Details on the principles of the method are found in the BioHCwin QMRF/QPRF (see cross-references).

Kinetic 301F model in the OASIS/LMC Catalogic software (v5.11.19) (Dimitrov et al., 2011a, 2011b) simulates aerobic biodegradation under OECD 301F test conditions and was run for all constituents in the category to determine the identity and persistence properties of the degradation products. Since the sediment is considered an aerobic system, similar methabolic pathways are considered to occur in water and sediment. An evaluation extrapolation factor of 4 was implemented to the metabolite primary water half-lives to calculate metabolite sediment primary half-lives for screening purposes, acording to Boethling et. al (1995). Details on the principles of the method are found in the CATALOGIC Kinetic 301F QMRF (see cross-references).

GLP compliance:

no

Oxygen conditions:

aerobic

Based on:

other: QSAR calculation

Parameter followed for biodegradation estimation:

other: QSAR calculation

Details on study design:

Not applicable

Key result

Compartment:

sediment

DT50:

>= 0.12 - <= 176.4 d

Remarks on result:

other: Result from 1:4 extrapolation from measured freshwater half-lives. Range based on the measured constituents in the streams. (Concawe 2019 report)

Key result

Compartment:

sediment

DT50:

>= 5.86 - <= 252.52 d

Remarks on result:

other: Result from 1:4 extrapolation from QSAR predicted freshwater half-lives. Range based on the measured constituents in the streams. (Extrapolation from BioHCWin QSAR)

Transformation products:

not measured

Remarks:

Potential metabolites of aerobic biodegradation and their relative concentrations are predicted using the Kinetic 301F model in the OASIS/LMC Catalogic software (v5.11.19)

Details on transformation products:

Potential metabolites of aerobic biodegradation and their relative concentrations have been predicted using the Kinetic 301F model in the OASIS/LMC Catalogic software (v5.11.19). The primary half-lives of metabolites have a range of half-lives from less than 4 days to 279.32 days and only 32 metabolites had half-lives of over one year. Only 16 metabolies have have log Kow values >4.5. However, none of the metabolites with half-lives of over one year had log Kow of greater than or equal to 4.5 and are therefore not considered to be bioaccumulative. (see attached Metabolite Persistence Evaluation Report)

Details on results:

Of the 240 parent constituents, 14 have a half-life greater than or equal to 120 days. Details of the constituent half-lives and how these value relate to their persistence assessment are found in the Persistence Weight of Evidence Evaluation (see cross-reference).

Validity criteria fulfilled:

not applicable

Conclusions:

The sediment half-lives of measured parent constituents of this category range from 5.86 to 252.52 days. Of the 240 parent constituents, 14 have a half-life greater than or equal to 120 days. Less than half of the parent constituents have a log Koc of < 3 which indicates that they will not preferentially adsorb to sediment particles and are therefore not considered to be persistent in sediments. The primary half-lives of metabolites have a range of half-lives from less than 4 days to 279.32 days and only 32 metabolites had half-lives of over one year. Only 16 metabolies have have log Kow values >4.5. However, none of the metabolites with half-lives of over one year had log Kow greater than or equal to 4.5 and are therefore not considered to be bioaccumulative.

Executive summary:

The sediment half-lives of the category constituents (at equal or above 0.1% w/w)  were extrapolated from measured (Concawe report, 2019) and predicted (EPISUITE v4.11 BioHCwin model, 2017) freshwater half-lives using an extrapolation factor of 4 (Boethling et al., 1995). The sediment half-lives of measured parent constituents of this category range from 5.86 to 252.52 days. Of the 46 parent constituents, 14 have a sediment half-life greater than or equal to 120 days. Less than half of the parent constituents have a log Koc of < 3 which indicates that they will not preferentially adsorb to sediment particles and are therefore not considered to be persistent in sediments

Potential metabolites of aerobic biodegradation and their relative concentrations have been predicted using the Kinetic 301F model in the OASIS/LMC Catalogic software (v5.11.19). The primary half-lives of metabolites have a range of half-lives from less than 4 days to 279.32 days and only 32 metabolites had half-lives of over one year. Only 16 metabolies have have log Kow values >4.5. However, none of the metabolites with half-lives of over one year had log Kow of greater than or equal to 4.5 and are therefore not considered to be bioaccumulative.

Description of key information

The predicted BioHCwin for measured constituents of this category (at equal or above 0.1% w/w) indicates that they are expected to have a half-life of 1.46 - 63.13 days in surface water. Of the 240 constituents, 4 have a half life of greater than 40 days.

We have utilised QSAR data as per Annex XI, Section 1.3 to fulfill the data requirements of this endpoint. It is not technically feasible to perform simulation testing on ultimate degradation in sediment on UVCBs. Current test procedures are not suitable for the characterisation of the degradation potential and potential metabolite formation of these substances due to their complex compositions.