Registration Dossier

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
calculation (if not (Q)SAR)
Remarks:
calculation using EAWAG-BBD Pathway Prediction System
Adequacy of study:
weight of evidence
Study period:
2020
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a (Q)SAR model, with limited documentation / justification, but validity of model and reliability of prediction considered adequate based on a generally acknowledged source
Justification for type of information:
1. SOFTWARE
The EAWAG-BBD Pathway Prediction System predicts microbial catabolic reactions using substructure searching, a rule-base, and atom-to-atom mapping. The system is able to recognize organic functional groups found in a compound and predict transformations based on biotransformation rules. The biotransformation rules are based on reactions found in the EAWAG-BBD database or in the scientific literature.

2. MODEL
The pathway prediction system can be accessed at the EAWAG-BBD Pathway Prediction page, which can be reached from the "Pathway Prediction" link on the EAWAG-BBD home page, or by using the following URL: http://umbbd.ethz.ch/predict/.

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
Substance name: dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated
Molecular formula: C30H20N4O3S
Molecular weight: 516.57 g/mol
Smiles notation: O=S(=O)(O)c1ccc(cc1)N4c7ccccc7N=C3C=C5N(c2ccccc2)c6ccccc6N=C5C=C34


4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint:
likelyhood of reaction

1. Very likely reaction.
This is to be reserved for reactions that will almost certainly occur and occur with the highest priority. For example, if an acid chloride is generated, these compounds almost invariably undergo spontaneous hydrolysis in water very rapidly. So this would likely occur as the next step in any metabolic pathway in any bacterium. EAWAG-BBD btrule bt0026, Acid chloride -> Carboxylate is an example of this type of rule.
2. Likely reaction.
This is to be used when almost all bacteria can catalyze a given reaction with a functional group present in a molecule. For example, if the substrate has an ester linkage, it is often hydrolyzed by very common esterases, found both extracellularly and intracellularly. So giving an ester hydrolysis rule a score of 2 would give it a high priority but after an acid chloride hydrolysis reaction. You should also use 2 for a reaction that is significantly likely to occur once a certain intermediate has been generated. For example, aromatic ring cis-dihydrodiols are likely to be dehydrogenated to form catechols. Most organisms that make cis-dihydrodiols will also catalyze their dehydrogenation, thus the latter reaction is likely due to the linkage. EAWAG-BBD btrule bt0255, Dihydrodihydroxyaromatic -> 1,2-Dihydroxyaromatic is an example of this type of rule.
3. Possible reaction (neutral).
This applies to reactions that are common but not certain to occur in every system. For example, hydrocarbon oxygenation reactions are quite possible, but may or may not be likely to occur depending on what the substrate is. These must be looked at individually. Some may be likely, some may be possible and some may be unlikely based on current knowledge (an example of the latter may be oxygenases that work on 5-ring polycyclic aromatic hydrocarbons). EAWAG-BBD btrule bt0002, secondary Alcohol -> Ketone is an example of this type of rule.
4. Unlikely reaction.
This would be the case for reactions that clearly might occur, but are either very rarely catalyzed in bacterial and fungal populations, or that don't seem likely to occur because of the initial conditions we are using or other chemical/biochemical reason. EAWAG-BBD btrule bt0029, organoHalide -> RH, which is unlikely to occur under aerobic conditions, is an example of this type of rule.
5. Very unlikely reaction.
These reactions are ones, for example, that have never been observed under aerobic conditions and the enzymes are oxygen sensitive. Thus, given our initial conditions, we would expect that these reactions are highly unlikely. EAWAG-BBD btrule bt0270, Toluene -> Benzylsuccinate is an example of this type of rule.
6. No decision.
- Defined domain of applicability:
Chemicals that are out of the scope of the model
1. Readily Degraded and Selected Other Compounds
PPS predictions will terminate when they reach certain small, readily degraded compounds. If one of these is entered, its biodegradation will not be predicted, and, if possible, the user will be given a link to a KEGG pathway that includes this compound. These compounds also include dead-end compounds that are not degraded and accumulate in the environment. A list of termination compounds in the current system is available. The PPS will not display many small molecules with few or no carbon atoms, and certain common enzyme cofactors and derivates, produced in a prediction. This limits the list of predicted compounds to the more important ones.
2. Inorganic Chemicals
The rules used for the PPS were designed and developed for organic chemicals. Results for inorganic chemicals will be unreliable and their biodegradation should not be predicted using the PPS. This class of chemicals includes all chemicals that do not contain carbon. It includes neutral species such as titanium dioxide (TiO2) and inorganic salts, such as sodium chloride (NaCl) or potassium permanganate (KMnO4). This class of chemicals also includes organo-metallic chemicals (chemicals that contain carbon bonded to a metal species).
3. High Molecular Weight Compounds
Polymers and chemicals with a molecular weight greater than 1,000 should not have their biodegradation predicted as the PPS was not developed for these types of compounds. However, many polymers may be made up of dimers, trimers, and oligomers that have a molecular weight of less than 1,000. These smaller molecules may contain the same components as the larger polymers, and, therefore, could be run through the PPS. The results should be interpreted with due caution, however, as the biodegradation characteristics of chemicals with a molecular weight of >1,000 are likely to be significantly different from that of much smaller compounds, even if they have similar structures. This is due at least in part to the greatly reduced bioavailability of high molecular weight compounds.
4. Chemicals with Unknown or Variable Composition
The PPS was developed for discrete organic chemicals. That is, organic chemicals that can be represented by a single, precisely known chemical structure. If the compound has a variable composition (such as oligomers, natural fats, or a product mixture that changes composition depending on environmental conditions), a representative structure may be entered. However, in that case, it is possible that PPS results do not reflect the true nature of the biodegradation products.
5. Mixtures
Mixtures cannot be run through the PPS because it uses a single, discrete chemical structure as its input. If the chemical whose biodegradation you want to predict is a mixture of discrete organic substances, then each substance can be run through the PPS separately. Results should be interpreted with caution, as the biodegradation pathways predicted for substances separately will possibly be very different if they were degraded together.
6. Highly Fluorinated Compounds
Many highly fluorinated chemicals (those that have more fluorines than non-fluorine atoms bonded to carbon), including fully fluorinated organics (those that have all hydrogens on carbon replaced with fluorine), possess biodegradation properties that are vastly different than their non-substituted analogs. The rules used by the PPS do not accurately predict the unique characteristics of these materials. All per- and highly- fluorinated chemicals should not have their biodegradation predicted.

Reactions the EAWAG-PPS does not predict:
Some known environmental reactions are not predicted. Some reactions are too complex to predict. Important classes of these reactions contain, but are not limited to:

- Detoxification reactions. These include, but are not limited to, conjugation with xylose, glucuronate and sulfate.
- Dimerizations. These include, but are not limited to, disulfides formed from sulfide (-SH) groups, or azo compounds formed from primary amide (-NH2) groups.
- Methylation of hydroxyl groups.
- Acetylation of primary amines.
- Formation of intramolecular rings.
- Hydroxylation of aliphatic carbon atoms at positions where pure cultures of organisms that metabolize similar compounds do not hydroxylate, though environmental non-specific monooxygenases may.

- unambigous algorithm:
The PPS predicts plausible pathways for microbial degradation of chemical compounds. Predictions use biotransformation rules, based on reactions found in the EAWAG-BBD database or in the scientific literature.

- Mechanistic interpretation:
The EAWAG-BBD contains 332 biotransformation descriptions for 249 biotransformation rules. These include 46 descriptions (*) for 25 super rules, and 39 rules subsumed by them (status June 29, 2017). The reaction rules to be evaluated are considered for biodegradation under aerobic conditions, in soil (moderate moisture) or water, at neutral pH, 25°C, with no competing or toxic other compounds. Biotransformation rules are prioritized using a five-point Likkert scoring scale.

5. APPLICABILITY DOMAIN
This molecule represents a group of isomers, which differ in the positions of the SO3 and C6H5 moieties. These isomers are the major constituent (42 %) of the registered substance and can thus be regarded as representative for it. The molecule is suitable for the model, as none of the criteria laid out for chemicals being out of scope are met.

- Similarity with analogues in the training set:
- Other considerations (as appropriate):

6. ADEQUACY OF THE RESULT
[Explain how the prediction fits the purpose of classification and labelling and/or risk assessment]
Reason / purpose:
reference to other study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: REACH Guidance on QSARs R.6
Version / remarks:
2008; R. 6.1.8.6
Principles of method if other than guideline:
Gao J, Ellis LBM, Wackett LP (2010) "The University of Minnesota Biocatalysis/Biodegradation Database: improving public access" Nucleic Acids Research 38: D488-D491.
GLP compliance:
no
Specific details on test material used for the study:
Substance name: dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated
Molecular formula: C30H20N4O3S
Molecular weight: 516.57 g/mol
Smiles notation: O=S(=O)(O)c1ccc(cc1)N4c7ccccc7N=C3C=C5N(c2ccccc2)c6ccccc6N=C5C=C34

This molecule represents a group of isomers, which differ in the positions of the SO3 and C6H5 moieties. These isomers are the major constituent (42 %) of the registered substance and can thus be regarded as representative for it. The molecule is suitable for the model, as none of the criteria laid out for chemicals being out of scope are met.
Although the sulfonic acid moieties within the registered substance are present as sodium salts, the protonated sulfonic acid moiety was used, due to the fact that the model does not allow the application of salts. However, the impact on the outcome of the model is of minor importance and can thus be neglected.
Radiolabelling:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: EAWAG-PPS used
Remarks:
Standard conditions assumed for aerobic biotransformations are: exposed to air, in moist soil or water, at neutral pH, 25°C, with no competing or toxic other compounds.
Details on source and properties of surface water:
The reaction rules to be evaluated are considered for biodegradation under aerobic conditions, in soil (moderate moisture) or water, at neutral pH, 25°C.
Parameter followed for biodegradation estimation:
other: likelyhood of reaction
Details on study design:
EAWAG-BBD Pathway Prediction System (PPS)

1. Purpose and Scope
The PPS predicts plausible pathways for microbial degradation of chemical compounds. Predictions use biotransformation rules, based on reactions found in the EAWAG-BBD database or in the scientific literature.
PPS predictions are most accurate for compounds that are:
1.1. similar to compounds whose biodegradation pathways are reported in the scientific literature
1.2. in environments exposed to air, in moist soil or water, at moderate temperatures and pH, with no competing chemicals or toxins; and
1.3. the sole source of energy, carbon, nitrogen, or other essential element for the microbes in these environments, rather than present in trace amounts


2. Biotransformation Rules
The EAWAG-BBD contains 332 biotransformation descriptions for 249 biotransformation rules. These include 46 descriptions (*) for 25 super rules, and 39 rules subsumed by them (status June 29, 2017). The reaction rules to be evaluated are considered for biodegradation under aerobic conditions, in soil (moderate moisture) or water, at neutral pH, 25°C, with no competing or toxic other compounds. Biotransformation rules are prioritized using a five-point Likkert scoring scale; instructions for its use are:
1. Very likely reaction.
This is to be reserved for reactions that will almost certainly occur and occur with the highest priority. For example, if an acid chloride is generated, these compounds almost invariably undergo spontaneous hydrolysis in water very rapidly. So this would likely occur as the next step in any metabolic pathway in any bacterium. EAWAG-BBD btrule bt0026, Acid chloride -> Carboxylate is an example of this type of rule.
2. Likely reaction.
This is to be used when almost all bacteria can catalyze a given reaction with a functional group present in a molecule. For example, if the substrate has an ester linkage, it is often hydrolyzed by very common esterases, found both extracellularly and intracellularly. So giving an ester hydrolysis rule a score of 2 would give it a high priority but after an acid chloride hydrolysis reaction. You should also use 2 for a reaction that is significantly likely to occur once a certain intermediate has been generated. For example, aromatic ring cis-dihydrodiols are likely to be dehydrogenated to form catechols. Most organisms that make cis-dihydrodiols will also catalyze their dehydrogenation, thus the latter reaction is likely due to the linkage. EAWAG-BBD btrule bt0255, Dihydrodihydroxyaromatic -> 1,2-Dihydroxyaromatic is an example of this type of rule.
3. Possible reaction (neutral).
This applies to reactions that are common but not certain to occur in every system. For example, hydrocarbon oxygenation reactions are quite possible, but may or may not be likely to occur depending on what the substrate is. These must be looked at individually. Some may be likely, some may be possible and some may be unlikely based on current knowledge (an example of the latter may be oxygenases that work on 5-ring polycyclic aromatic hydrocarbons). EAWAG-BBD btrule bt0002, secondary Alcohol -> Ketone is an example of this type of rule.
4. Unlikely reaction.
This would be the case for reactions that clearly might occur, but are either very rarely catalyzed in bacterial and fungal populations, or that don't seem likely to occur because of the initial conditions we are using or other chemical/biochemical reason. EAWAG-BBD btrule bt0029, organoHalide -> RH, which is unlikely to occur under aerobic conditions, is an example of this type of rule.
5. Very unlikely reaction.
These reactions are ones, for example, that have never been observed under aerobic conditions and the enzymes are oxygen sensitive. Thus, given our initial conditions, we would expect that these reactions are highly unlikely. EAWAG-BBD btrule bt0270, Toluene -> Benzylsuccinate is an example of this type of rule.
6. No decision.
This is reserved for cases where you cannot assign a number for whatever reason.


3. Chemicals that are out of the scope of the model

3.1. Readily Degraded and Selected Other Compounds
PPS predictions will terminate when they reach certain small, readily degraded compounds. If one of these is entered, its biodegradation will not be predicted, and, if possible, the user will be given a link to a KEGG pathway that includes this compound. These compounds also include dead-end compounds that are not degraded and accumulate in the environment. A list of termination compounds in the current system is available. The PPS will not display many small molecules with few or no carbon atoms, and certain common enzyme cofactors and derivates, produced in a prediction. This limits the list of predicted compounds to the more important ones.
3.2. Inorganic Chemicals
The rules used for the PPS were designed and developed for organic chemicals. Results for inorganic chemicals will be unreliable and their biodegradation should not be predicted using the PPS. This class of chemicals includes all chemicals that do not contain carbon. It includes neutral species such as titanium dioxide (TiO2) and inorganic salts, such as sodium chloride (NaCl) or potassium permanganate (KMnO4). This class of chemicals also includes organo-metallic chemicals (chemicals that contain carbon bonded to a metal species).
3.3. High Molecular Weight Compounds
Polymers and chemicals with a molecular weight greater than 1,000 should not have their biodegradation predicted as the PPS was not developed for these types of compounds. However, many polymers may be made up of dimers, trimers, and oligomers that have a molecular weight of less than 1,000. These smaller molecules may contain the same components as the larger polymers, and, therefore, could be run through the PPS. The results should be interpreted with due caution, however, as the biodegradation characteristics of chemicals with a molecular weight of >1,000 are likely to be significantly different from that of much smaller compounds, even if they have similar structures. This is due at least in part to the greatly reduced bioavailability of high molecular weight compounds.
3.4. Chemicals with Unknown or Variable Composition
The PPS was developed for discrete organic chemicals. That is, organic chemicals that can be represented by a single, precisely known chemical structure. If the compound has a variable composition (such as oligomers, natural fats, or a product mixture that changes composition depending on environmental conditions), a representative structure may be entered. However, in that case, it is possible that PPS results do not reflect the true nature of the biodegradation products.
3.5. Mixtures
Mixtures cannot be run through the PPS because it uses a single, discrete chemical structure as its input. If the chemical whose biodegradation you want to predict is a mixture of discrete organic substances, then each substance can be run through the PPS separately. Results should be interpreted with caution, as the biodegradation pathways predicted for substances separately will possibly be very different if they were degraded together.
3.6. Highly Fluorinated Compounds
Many highly fluorinated chemicals (those that have more fluorines than non-fluorine atoms bonded to carbon), including fully fluorinated organics (those that have all hydrogens on carbon replaced with fluorine), possess biodegradation properties that are vastly different than their non-substituted analogs. The rules used by the PPS do not accurately predict the unique characteristics of these materials. All per- and highly- fluorinated chemicals should not have their biodegradation predicted.
Compartment:
natural water
Remarks on result:
not determinable
Remarks:
calculation of likelihood
Parameter:
other:
Remarks on result:
not determinable
Remarks:
calculation of likelyhood
Remarks on result:
not determinable
Transformation products:
not measured
Evaporation of parent compound:
no
Remarks:
due to high water solubility
Volatile metabolites:
not measured
Residues:
not measured
Details on results:
First transformation step
In a first transformation step four different possible biotransformations were found. Only one of these transformation processes (bt0353) is to be considered as likely (score 2). This rule handles the 2,3-dioxygenation of mono-substituted aromatics (bt0369) and subsequent oxidation to form the catechol derivative (bt0255). The formed product was used as the starting point for the second transformation step.

Second transformation step
In the second transformation step two possible biotransformations were found, only one of which (bt0351) is to be considered as likely (score 2). This rule handles extradiol (meta) ring cleavage for vic-dihydroxybenzenoids forming 2-hydroxymuconate semialdehyde derivatives, respectively. Hydrolysis of the C5-C6 bond (bt0040), or oxidation of the aldehyde to a carboxylate (bt0003), followed by decarboxylation (bt0051), produces a 2-amino-2,4-dienoate derivative or an enol product, which quickly tautomerizes to a 2-oxopent-4-enoate derivative. However, the remaining part of the molecule is structurally still very similar to the initial educt and the model does not reveal any further biotransformation processes, which are likely to occur.

First transformation step

In a first transformation step four different possible biotransformations were found. Only one of these transformation processes (bt0353) is to be considered as likely (score 2). This rule handles the 2,3-dioxygenation of mono-substituted aromatics (bt0369) and subsequent oxidation to form the catechol derivative (bt0255). The formed product was used as the starting point for the second transformation step.

Second transformation step

In the second transformation step two possible biotransformations were found, only one of which (bt0351) is to be considered as likely (score 2). This rule handles extradiol (meta) ring cleavage for vic-dihydroxybenzenoids forming 2-hydroxymuconate semialdehyde derivatives, respectively. Hydrolysis of the C5-C6 bond (bt0040), or oxidation of the aldehyde to a carboxylate (bt0003), followed by decarboxylation (bt0051), produces a 2-amino-2,4-dienoate derivative or an enol product, which quickly tautomerizes to a 2-oxopent-4-enoate derivative. However, the remaining part of the molecule is structurally still very similar to the initial educt and the model does not reveal any further biotransformation processes, which are likely to occur.

Validity criteria fulfilled:
not applicable
Conclusions:
Applying the EAWAG-BBD Pathway Prediction System (PPS) to the molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” not a single biotransformation pathway could be found, which can be considered as very likely (score 1) to occur. For the applied molecule most of the possible biotransformations are rated neutral (score 3) and only one transformation path way can be considered as likely to occur. Thus, the model does not predict a significant potential for biodegradation. Instead, only minor changes of the molecular structure, limited to the phenylic moiety, can be expected. The arising transformation products are therefore structurally very similar to the initial educt. Taking this into account the obtained model data strongly point at a low potential for biodegradation for the representative molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” and as a consequence also for the registered substance “Hydrochloric acid, reaction products with aniline and nitrobenzene, sulfonated, sodium salts” CAS no.: 90411-76-0”.
Executive summary:

Applying the EAWAG-BBD Pathway Prediction System (PPS) to the molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” yields valuable information about the putative environmental fate of the substance. From the vast amount of possible biotransformation processes not a single one could be found, which can be considered as very likely (score 1) to occur. For the applied molecule most of the possible biotransformations are rated neutral (score 3) and only one transformation path way can be considered as likely to occur. However, this pathway only affects the phenylic moiety of the molecule, while the rest of the molecule does not undergo any further  structural changes. Thus, the model does not predict a significant potential for biodegradation. Instead, only minor changes of the molecular structure, limited to the phenylic moiety, can be expected.  The arising transformation products are therefore structurally very similar to the initial educt. It has to be noted that the investigated molecule acts only as a representative candidate for the registered substance. Taking this into account the obtained model data strongly point at a low potential for biodegradation for the representative molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” and as a consequence also for the registered substance “Hydrochloric acid, reaction products with aniline and nitrobenzene, sulfonated, sodium salts” CAS no.: 90411-76-0”.

Description of key information

Weight-of-evidence approach

Applying a weight-of-evidence approach the results derived from QSAR calculations employing

dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated and experimental data from the test on inherent biodegradation of the substance are evaluated.

QSAR employing EAWAG-BBD Pathway Prediction System

Applying the EAWAG-BBD Pathway Prediction System (PPS) to the molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” yields valuable information about the putative environmental fate of the substance. The found pathway only affects the phenylic moiety of the molecule, while the rest of the molecule does not undergo any further structural changes. Thus, the model does not predict a significant potential for biodegradation.

The investigated molecule acts only as a representative candidate for the registered substance. However, it's isomers are the major constituent (42 %). Taking this into account the obtained model data strongly point at a low potential for biodegradation for the representative molecule “dihydro-5,7,12,14-tetraazapentacene, diphenylated, monosulfonated” and as a consequence also for the registered substance “Hydrochloric acid, reaction products with aniline and nitrobenzene, sulfonated, sodium salts” CAS no.: 90411-76-0”.

Data from screening tests

In addition a study by Kanne (1987) could find only a degradation of 30 % after 28 days, this study is referenced under Endpoint 5.2.1 Biodegradation in water: screening tests in this dossier. The substance is therefore neither inherently nor rapidly biodegradable in water.

In conclusion the substance can be regarded as not biodegradable in sediment or surface water as well. The performance of simulation tests would not provide additional information for the hazard, risk and persistency assessment. As the substance neither fulfills the B, nor the T criterion, no further information is required for the PBT assessment (Guidance Document R.7b, ECHA, 2014; Guidance Document R.11, ECHA, 2014).

Key value for chemical safety assessment

Additional information