Hydrocarbons, C3-6, C5-rich, steam-cracked naphtha

Biodegradation in soil

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in soil: simulation testing

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

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 soil. This indicates that the surface water biodegradation rates measured or predicted using QSARs would be applicable to soil. An evaluation extrapolation factor of 1 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 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 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:

An evaluation extrapolation factor of 1 was implemented to the water half-lives to calculate soil 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 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 soil is considered an aerobic system, similar methabolic pathways are considered to occur in water and soil. An evaluation extrapolation factor of 1 was implemented to the metabolite primary water half-lives to calculate metabolite soil 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).

Key result

DT50:

>= 3.11 - <= 44.1 d

Remarks on result:

other: Result from 1:1 extrapolation from measured freshwater half-lives. Range based on the measured constituents in the streams

Key result

DT50:

>= 1.56 - <= 55.38 d

Remarks on result:

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

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:

All 46 parent constituents were evaluated using the model and this resulted in the prediction of 101 metabolites of which 32 were unique metabolites/degradation products. Review of the log Kow information indicates that none of the parent constituents would be considered to be bioaccumulative and therefore are not PBT. This evaluation is fully reported in the PBT report for the category which is attached to Section 13 of the IUCLID dossier. Two metabolites were considered to be readily biodegradable and 30 not readily biodegradable. However, the primary half-lives indicate that the constituents have a range of half-lives from less than one day to 21 days and only three metabolites had half-lives of over one year. Predicted metabolite structures and abundance are contained in full in the file attached in background material.

Details on results:

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).

Conclusions:

The soil half-lives of measured parent constituents of this category range from 1.56 to 55.38 days. Of the 46 parent constituents, five have a half-life of greater equal or greater than 40 days. The five constituents with half-lives of >40 days were not considered to be persistent in soil because they would preferentially reside in air where abiotic processes would degrade them within six days. Finally, most of the parent constituents have a log Koc of < 3 which indicates that they will not adsorb to soil particles and are therefore not considered to be persistent in soils. The primary half-lives of metabolites have a range of half-lives from less than one day to 22 days and only five metabolites had half-lives of over one year. All the metabolies have log Kow values well below the B threshold and as such are not expected to be PBT or vPvB.

Executive summary:

The soil half-lives of measured constituents (at equal or above 0.1% w/w) of this category have been extrapolated from measured (Concawe report, 2019) and predicted (EPISUITE v4.11 BioHCwin model, 2017) freshwater half-lives using an extrapolation factor of 1:1 (Boethling et al., 1995). The soil half-lives of measured parent constituents of this category range from 1.56 to 55.38 days. Of the 46 parent constituents, five have a half-life of greater equal or greater than 40 days. The five constituents with half-lives of >40 days were not considered to be persistent in soil because they would preferentially reside in air where abiotic processes would degrade them within six days. Finally, most of the parent constituents have a log Koc of < 3 which indicates that they will not adsorb to soil particles and are therefore not considered to be persistent in soil.

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 one day to 22 days and only three metabolites had half-lives of over one year. All the metabolies have log Kow values well below the B threshold and as such are not expected to be PBT or vPvB.

Reference 2

Endpoint:

biodegradation in soil: simulation testing

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Combination of experimental data and QSAR calculations

Justification for type of information:

Several lines of evidence are used to evaluate the degradation potential of the constituents reported in UVCBs. This includes any experimental degradation data available, degradation QSARs, and any other data that would influence the ultimate fate of the constituents in the environment including the log Kow for bioaccumulation potential and the log Koc to evaluate the potential of the constituents to adsorb to sediment and soil particles. See cross-reference.

Reason / purpose for cross-reference:

assessment report

Principles of method if other than guideline:

Several lines of evidence are used to evaluate the degradation potential of the constituents reported in UVCBs. This includes any experimental degradation data available, degradation QSARs, and any other data that would influence the ultimate fate of the constituents in the environment including the log Kow for bioaccumulation potential and the log Koc to evaluate the potential of the constituents to adsorb to sediment and soil particles. See cross-reference.

DT50:

>= 1.56 - <= 55.38 d

Remarks on result:

other: Result from 1:1 extrapolation from experimental and QSAR predicted freshwater half-lives. Range based on the measured constituents in the streams.

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:

All 46 parent constituents were evaluated using the model and this resulted in the prediction of 101 metabolites of which 32 were unique metabolites/degradation products. Review of the log Kow information indicates that none of the parent constituents would be considered to be bioaccumulative and therefore are not PBT. This evaluation is fully reported in the PBT report for the category which is attached to Section 13 of the IUCLID dossier. Two metabolites were considered to be readily biodegradable and 30 not readily biodegradable. However, the primary half-lives indicate that the constituents have a range of half-lives from less than one day to 21 days and only three metabolites had half-lives of over one year. Predicted metabolite structures and abundance are contained in full in the file attached in background material.

Details on results:

The persistence assessment for this category was conducted by evaluating the individual constituents reported by the registrants (co- and lead) at a concentration of = 0.1% (w/w). The degradation potential in surface water indicated that the constituents would not be persistent if released to water. The category constituents’ degradation evaluation indicated that when physico-chemical properties (e.g., volatilization), abiotic and biotic processes are addressed collectively none of the constituents would persist in surface water. Therefore, simulation testing on ultimate degradation in surface water does not appear to be scientifically necessary. The adsorption/desorption potential evaluated for the category constituents using the log Koc screening criterion value of 3 indicates that the constituents do not have significant adsorption potential. Therefore, sediment and soil biodegradation simulation tests do not appear to be scientifically necessary as the category constituents degrade rapidly in the environment and there is very low potential for them to adsorb to sediment and soil particles.

Conclusions:

In accordance to REACH Annex XI, Section 1.2 the surface water, sediment and soil biodegradation simulation studies are not required because the weight of evidence indicates that the constituents in the category would degrade rapidly in the environment and because their potential for adsorption to sediment and soil particles is considered to be low based on the log Koc criteria of 3.

Executive summary:

The persistence assessment for this category was conducted by evaluating the individual constituents reported by the registrants (co- and lead) at a concentration of = 0.1% (w/w).

The degradation potential in surface water indicated that the constituents would not be persistent if released to water. The category constituents’ degradation evaluation indicated that when physico-chemical properties (e.g., volatilisation), abiotic and biotic processes are addressed collectively none of the constituents would persist in surface water. Therefore, simulation testing on ultimate degradation in surface water does not appear to be scientifically necessary.

The adsorption/desorption potential evaluated for the category constituents using the log Koc screening criterion value of 3 indicates that the constituents do not have significant adsorption potential. Therefore, sediment and soil biodegradation simulation tests do not appear to be scientifically necessary as the category constituents degrade rapidly in the environment and there is very low potential for them to adsorb to sediment and soil particles.

In accordance to REACH Annex XI, Section 1.2 the surface water, sediment and soil biodegradation simulation studies are not required because the weight of evidence indicates that the constituents in the category would degrade rapidly in the environment and because their potential for adsorption to sediment and soil particles is considered to be low based on the log Koc criteria of 3.

Description of key information

It is not technically feasible to perform simulation testing on ultimate degradation in sediment, surface water or soil 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. For this reason, the persistence assessment for this category was conducted by evaluating the individual constituents reported by the registrants (co- and lead) at a concentration of = 0.1% (w/w).

The degradation potential in surface water indicated that the constituents would not be persistent if released to water. The category constituents’ degradation evaluation indicated that when physico-chemical properties (e.g., volatilization), abiotic and biotic processes are addressed collectively none of the constituents would persist in surface water. Therefore, simulation testing on ultimate degradation in surface water does not appear to be scientifically necessary.

The adsorption/desorption potential evaluated for the category constituents using the log Koc screening criterion value of 3 indicates that the constituents do not have significant adsorption potential. Therefore, sediment and soil biodegradation simulation tests do not appear to be scientifically necessary as the category constituents degrade rapidly in the environment and there is very low potential for them to adsorb to sediment and soil particles.

Additional information

The soil half-lives of measured constituents (at equal or above 0.1% w/w) of this category have been extrapolated from measured (Concawe report, 2019) and predicted (EPISUITE v4.11 BioHCwin model, 2017) freshwater half-lives using an extrapolation factor of 1:1 (Boethling et al., 1995). The soil half-lives of measured parent constituents of this category range from 1.56 to 55.38 days. Of the 46 parent constituents, five have a half-life of greater equal or greater than 40 days. The five constituents with half-lives of >40 days were not considered to be persistent in soil because they would preferentially reside in air where abiotic processes would degrade them within six days. Finally, most of the parent constituents have a log Koc of < 3 which indicates that they will not adsorb to soil particles and are therefore not considered to be persistent in soil.

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 one day to 22 days and only three metabolites had half-lives of over one year. All the metabolies have log Kow values well below the B threshold and as such are not expected to be PBT or vPvB.