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EC number: 210-762-8 | CAS number: 622-97-9
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data

Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
- Endpoint:
- biodegradation in water: ready biodegradability
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- From November 9, 1979 to November 28, 1979
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- test procedure in accordance with generally accepted scientific standards and described in sufficient detail
- Qualifier:
- according to guideline
- Guideline:
- other: Standard Methods for the Examination of Water and Wastewater, 14th edition (1976)
- Principles of method if other than guideline:
- The method was designed to determine biological oxygen demand (BOD) and chemical oxygen demand (COD). Modifications to the study guideline included the use of a carbon standard and extension of the usual test period from 5 to 20 d. In addition, re-oxygenation was conducted at intervals to maintain a concentration of >2mg/L dissolved oxygen.
- GLP compliance:
- not specified
- Remarks:
- At the time this study was conducted GLP was not required for chemical testing.
- Oxygen conditions:
- aerobic
- Remarks:
- >2mg/L
- Inoculum or test system:
- sewage, domestic, non-adapted
- Details on inoculum:
- no information is provided on the innoculum used.
- Duration of test (contact time):
- 20 d
- Initial conc.:
- > 2 - < 4 other: uL/300ml
- Based on:
- test mat.
- Parameter followed for biodegradation estimation:
- other: BOD
- Parameter followed for biodegradation estimation:
- other: COD
- Details on study design:
- The study it was conducted in 300 ml BOD bottles. The test substance was evaluated at two concentrations 2 and 4 uL/300 ml and analysed at 5, 10, 15 and 20 days. The results were compare with results obtained from the glucose and the glucose/glutamic acid control. Re-aeration was conducted as necessary to maintain dissolved oxygen concentrations at levels >2 mg/L.
- Key result
- Parameter:
- % degradation (O2 consumption)
- Value:
- > 3
- Sampling time:
- 5 d
- Key result
- Parameter:
- % degradation (O2 consumption)
- Value:
- 6
- Sampling time:
- 10 d
- Key result
- Parameter:
- % degradation (O2 consumption)
- Value:
- 13
- Sampling time:
- 15 d
- Key result
- Parameter:
- % degradation (O2 consumption)
- Value:
- 32
- Sampling time:
- 20 d
- Details on results:
- The BOD showed initial slow by bio-oxidation that increased through time to 32 % after 20 days indicating that the unadapted microbial population in the domestic sewage sample used in the study required time to adapt to degrade the test substance.
The COD expressed as mg oxygen/mg was measured at 2.24 which compared well with a calculated value of 3.1. - Key result
- Parameter:
- COD
- Value:
- 2.24 g O2/g test mat.
- Remarks on result:
- other: measured
- Results with reference substance:
- The glucose/glutamic acid control analysed after five days gave 99.1% of the theoretical oxygen demand indicating that the sewage sample used was performing effectively.
- Validity criteria fulfilled:
- not specified
- Interpretation of results:
- under test conditions no biodegradation observed
- Conclusions:
- Under the study conditions, unadapted microorganisms therefore could not degrade the test substance within a 28 d period to a level allowing identification as readily biodegradable. Nevertheless, adapted microorganisms present where continuous exposure to the test substance occurs will readily remove the test substance from sewage systems.
- Executive summary:
A study was conducted to determine the Biological Oxygen Demand (BOD) and the Chemical Oxygen Demand (COD) of the test substance according to US Standard Methods for the Examination of Water and Wastewater (1976). The method was modified to include analyses at additional time points after inoculation with domestic sewage sludge (10, 15 and 20 d) in order to determine whether the microorganisms required a time interval to adapt to the new food source (test substance). Exposure to the test substance occurred at a concentration of 2 to 4 µL/300 ml. The control groups confirmed that the inoculum was active and the results indicated that adaptation was necessary in order for domestic sludge microorganisms to utilise the test substance as a substrate. Under the study conditions, 13% of test substance was removed in the first 15 d of the sampling period and 32% was degraded from 15 to 20 d. Under the study conditions, unadapted microorganisms therefore could not degrade the test substance within a 28 d period to a level allowing identification as readily biodegradable. Nevertheless, adapted microorganisms present where continuous exposure to the test substance occurs will readily remove the substance from sewage systems (Gezo, 1980).
- Endpoint:
- biodegradation in water: screening test, other
- Type of information:
- (Q)SAR
- Adequacy of study:
- supporting 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:
- QSAR prediction from an well known and acknowledged tool. See below under 'Overall remarks, attachments' for applicability domain and 'attached background material section' for methodology.
- Qualifier:
- according to guideline
- Guideline:
- other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals
- GLP compliance:
- no
- Key result
- Parameter:
- half-life in days (QSAR/QSPR)
- Value:
- ca. 3.897
- Remarks on result:
- readily biodegradable based on QSAR/QSPR prediction
- Validity criteria fulfilled:
- not applicable
- Interpretation of results:
- readily biodegradable
- Conclusions:
- Based on the BioHCwin model result, the primary biodegradation half-life for the test substance was determined to be 3.897 days and it was considered to be readily biodegradable.
- Executive summary:
The biodegradation potential of the test substance, p-methylstyrene, was estimated using the BioHCwin v1.01 program of EPI Suite v4.11. BioHCwin is a new predictive model within EPI Suite, which determines quantitative primary biodegradation half-lives of individual petroleum hydrocarbons. This model uses a fragment-based approach similar to BioWin. Using SMILES code as the input parameter the primary biodegradation half-life for the test substance was determined to be 3.897 days; indicating that the substance can be considered to be readily biodegradable (US EPA, 2018). The prediction for the substance is considered to be reliable, as it falls within of the applicability domain.
- Endpoint:
- biodegradation in water: screening test, other
- Type of information:
- (Q)SAR
- Adequacy of study:
- supporting 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:
- QSAR prediction from an well known and acknowledged tool. See below under 'Overall remarks, attachments' for applicability domain and 'attached background material section' for methodology.
- Qualifier:
- according to guideline
- Guideline:
- other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals
- GLP compliance:
- no
- Key result
- Parameter:
- other: Biowin1 (Linear Model Prediction)
- Remarks on result:
- other: Biodegrades fast
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin2 (Non-Linear Model Prediction)
- Remarks on result:
- other: Biodegrades fast
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin3 (Ultimate Biodegradation Timeframe):
- Remarks on result:
- other: Weeks
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin4 (Primary Biodegradation Timeframe):
- Remarks on result:
- other: Days-Weeks
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin5 (MITI Linear Model Prediction)
- Remarks on result:
- other: Not readily degradable
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin6 (MITI Non-Linear Model Prediction):
- Remarks on result:
- other: Not readily degradable
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Biowin7 (Anaerobic Model Prediction):
- Remarks on result:
- other: Does not biodegrade fast
- Remarks:
- (prediction as per EPISuite BioWin 4.11)
- Key result
- Parameter:
- other: Ready Biodegradability Prediction
- Remarks on result:
- other: No
- Remarks:
- (prediction as per EPISuite BioWin v 4.11)
- Validity criteria fulfilled:
- not applicable
- Interpretation of results:
- not readily biodegradable
- Conclusions:
- Based on the BIOWIN v4.11 model estimation, the test substance is predicted to be not readily biodegradable. The individual submodules (i.e., BioWin 2 and 3 or BioWin 3 and 6) however suggest that the substance do not meet the persistence criteria as per Annex XIII criteria as set out in the REACH Technical Guidance Document Chapter R.11 (Table R.11—4).
- Executive summary:
The biodegradation potential of the test substance, p-methylstyrene, was estimated using the BioWin v4.11 program of EPI Suite v4.11. BIOWIN contains seven separate models.This version (v4.11) designates the models as Biowin1 (linear probability model), Biowin2 (nonlinear probability model), Biowin3 (expert survey ultimate biodegradation model), Biowin4 (expert survey primary biodegradation model), Biowin5 (MITI linear model), Biowin6 (MITI nonlinear model), Biowin7 (anaerobic biodegradation model). Using SMILES or CAS number as the input parameter, the biodegradability estimates are based upon fragment constants that were developed using multiple linear or non-linear regression analyses, depending upon the model. For p-methylstyrene, the Biowin 1 and Biowin 2 models both predicted 'biodegrades fast, Biowin3 and Biowin 4 predicted 'weeks' and 'days-weeks' respectively, Biowin 5 and Biowin 6 both predicted 'not readily biodegradable' (with probability of biodegradation as 0.36 and 0.387 respectively) and Biowin 7 predicted 'does not biodegrade fast'. As the criteria for overall 'yes' ready biodegradability prediction is based on the 'weeks' or faster and biodegradation probability of >=0.5 predictions by Biowin 3 and Biowin 5 respectively, the overall ready biodegradability prediction for the substance was 'No' (US EPA, 2018). The individual submodules (i.e., BioWin 2 and 3 or BioWin 3 and 6), however suggest that the substance do not meet the persistence criteria as per Annex XIII criteria as set out in the REACH Technical Guidance Document Chapter R.11 (Table R.11—4). Overall, the prediction for the substance is considered to be reliable, as it falls within of the applicability domain.
Referenceopen allclose all
Test substance |
COD mg oxygen/mg compound |
|
Measured |
Calculated |
|
purity 97% |
2.24 |
3.1 |
Test substance |
Bio-oxidation (BOD x100) ThOD |
|||
Day 5 |
Day 10 |
Day 15 |
Day 20 |
|
purity 97% |
3.0 |
6.0 |
13.0 |
32.0 |
The results from an earlier study gave the following data.
Test substance |
Bio-oxidation (BOD x100) ThOD |
|||
Day 5 |
Day 10 |
Day 15 |
Day 20 |
|
purity 97% |
3.0 |
24.0 |
26.0 |
34.0 |
Results
Chemical | SMILES | Molecular weight | BioHCwin results (Half life - days) | domain evaluation |
p-methylstyrene | CC1=CC=C(C=C1)C=C | 118.18 | 3.897 | In domain - molecular weight and molecular fragments |
BioHCwin |
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SMILES : Cc1ccc(cc1)C=C |
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CHEM : |
Domain |
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MOL FOR: C9 H10 |
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MOL WT : 118.18 |
ID |
70.14 |
478.94 |
-------------------------- BioHCwin v1.01 Results --------------------------- |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | LOG Hydrocarbon FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
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|
Frag | 1 | Aromatic-CH3 | 0.0369 | 0.0369 |
ID |
4 |
|
Frag | 4 | Aromatic-H | 0.0419 | 0.1678 |
ID |
14 |
|
Frag | 3 | -C=CH [alkenyl hydrogen] | -0.0066 | -0.0199 |
ID |
6 |
|
Frag | 1 | Benzene | -0.0838 | -0.0838 |
ID |
1 |
|
Const| * | Equation Constant | | 0.4898 |
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============+============================================+=========+========= |
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RESULT | LOG BioHC Half-Life (days) | | 0.5907 |
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RESULT | BioHC Half-Life (days) | | 3.897 |
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============+============================================+=========+========= |
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Results
Chemical |
SMILES |
Molecular weight |
Biowin results |
domain evaluation |
p -methylstyrene |
Cc1cccc(c1)C=C |
118.18 |
Biowin1 (Linear Model Prediction): Biodegrades Fast |
In domain - molecular weight and molecular fragments |
BIOWIN |
|||
SMILES : Cc1cccc(c1)C=C |
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CHEM : |
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MOL FOR: C9 H10 |
|
Training set |
|
MOL WT : 118.18 |
ID |
30.02 |
697.65 |
--------------------------- BIOWIN v4.10 Results ---------------------------- |
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Biowin1 (Linear Model Prediction) : Biodegrades Fast |
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Biowin2 (Non-Linear Model Prediction): Biodegrades Fast |
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Biowin3 (Ultimate Biodegradation Timeframe): Weeks |
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Biowin4 (Primary Biodegradation Timeframe): Days-Weeks |
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Biowin5 (MITI Linear Model Prediction) : Not Readily Degradable |
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Biowin6 (MITI Non-Linear Model Prediction): Not Readily Degradable |
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Biowin7 (Anaerobic Model Prediction): Does Not Biodegrade Fast |
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Ready Biodegradability Prediction: NO |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin1 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Alkyl substituent on aromatic ring | 0.0547 | 0.0547 |
ID |
3 |
|
MolWt| * | Molecular Weight Parameter | | -0.0563 |
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Const| * | Equation Constant | | 0.7475 |
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============+============================================+=========+========= |
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RESULT | Biowin1 (Linear Biodeg Probability) | | 0.7460 |
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============+============================================+=========+========= |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin2 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Alkyl substituent on aromatic ring | 0.5771 | 0.5771 |
ID |
3 |
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MolWt| * | Molecular Weight Parameter | | -1.6782 |
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============+============================================+=========+========= |
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RESULT | Biowin2 (Non-Linear Biodeg Probability) | | 0.8708 |
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============+============================================+=========+========= |
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A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast |
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A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin3 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
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Training set |
|
Frag | 1 | Alkyl substituent on aromatic ring | -0.0749 | -0.0749 |
ID |
3 |
|
MolWt| * | Molecular Weight Parameter | | -0.2612 |
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Const| * | Equation Constant | | 3.1992 |
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============+============================================+=========+========= |
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RESULT | Biowin3 (Survey Model - Ultimate Biodeg) | | 2.8632 |
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============+============================================+=========+========= |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin4 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Alkyl substituent on aromatic ring | -0.0685 | -0.0685 |
ID |
3 |
|
MolWt| * | Molecular Weight Parameter | | -0.1705 |
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Const| * | Equation Constant | | 3.8477 |
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============+============================================+=========+========= |
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RESULT | Biowin4 (Survey Model - Primary Biodeg) | | 3.6087 |
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============+============================================+=========+========= |
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Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks |
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(Primary & Ultimate) 2.00 -> months 1.00 -> longer |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin5 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Aromatic-CH3 | 0.0415 | 0.0415 |
ID |
3 |
|
Frag | 4 | Aromatic-H | 0.0082 | 0.0329 |
ID |
15 |
|
Frag | 3 | -C=CH [alkenyl hydrogen] | 0.0062 | 0.0186 |
ID |
9 |
|
MolWt| * | Molecular Weight Parameter | | -0.3516 |
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Const| * | Equation Constant | | 0.7121 |
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============+============================================+=========+========= |
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RESULT | Biowin5 (MITI Linear Biodeg Probability) | | 0.4535 |
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============+============================================+=========+========= |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin6 FRAGMENT DESCRIPTION | COEFF | VALUE |
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Aromatic-CH3 | 0.3072 | 0.3072 |
ID |
3 |
|
Frag | 4 | Aromatic-H | 0.1201 | 0.4806 |
ID |
15 |
|
Frag | 3 | -C=CH [alkenyl hydrogen] | 0.0285 | 0.0855 |
ID |
9 |
|
MolWt| * | Molecular Weight Parameter | | -3.4117 |
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============+============================================+=========+========= |
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RESULT |Biowin6 (MITI Non-Linear Biodeg Probability)| | 0.4968 |
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============+============================================+=========+========= |
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A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable |
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A Probability Less Than 0.5 indicates --> NOT Readily Degradable |
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------+-----+--------------------------------------------+---------+--------- |
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TYPE | NUM | Biowin7 FRAGMENT DESCRIPTION | COEFF | VALUE |
|
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------+-----+--------------------------------------------+---------+--------- |
|
Training set |
|
Frag | 1 | Alkyl substituent on aromatic ring | -0.1145 | -0.1145 |
ID |
3 |
|
Frag | 1 | Aromatic-CH3 | -0.2573 | -0.2573 |
ID |
3 |
|
Frag | 4 | Aromatic-H | -0.0954 | -0.3817 |
ID |
13 |
|
Frag | 3 | -C=CH [alkenyl hydrogen] | -0.0735 | -0.2206 |
ID |
11 |
|
Const| * | Equation Constant | | 0.8361 |
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============+============================================+=========+========= |
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RESULT | Biowin7 (Anaerobic Linear Biodeg Prob) | | -0.1380 |
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============+============================================+=========+========= |
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A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast |
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A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast |
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Ready Biodegradability Prediction: (YES or NO) |
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---------------------------------------------- |
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Criteria for the YES or NO prediction: If the Biowin3 (ultimate survey |
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model) result is "weeks" or faster (i.e. "days", "days to weeks", or |
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"weeks" AND the Biowin5 (MITI linear model) probability is >= 0.5, then |
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the prediction is YES (readily biodegradable). If this condition is not |
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satisfied, the prediction is NO (not readily biodegradable). This method |
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is based on application of Bayesian analysis to ready biodegradation data |
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(see Help). Biowin5 and 6 also predict ready biodegradability, but for |
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degradation in the OECD301C test only; using data from the Chemicals |
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Evaluation and Research Institute Japan (CERIJ) database. |
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Description of key information
In accordance with the restricted definition of readily biodegradable in screening tests used in the context of the REACH directive the substance must be considered to be not readily biodegradable as preconditioning of the microorganisms is required as per the experimental study with the test substance. However, the individual submodule prediction from BioWin as well as half-life prediction from BioHCwin model of EPI Suite QSAR program, indicate that the substance is biodegradable and will not be persistent in the environment.
Key value for chemical safety assessment
- Biodegradation in water:
- under test conditions no biodegradation observed
- Type of water:
- freshwater
Additional information
Experimental study
A study was conducted to determine the Biological Oxygen Demand (BOD) and the Chemical Oxygen Demand (COD) of the test substance, p -methylstyrene according to US Standard Methods for the Examination of Water and Wastewater (1976). The method was modified to include analyses at additional time points after inoculation with domestic sewage sludge (10, 15 and 20 d) in order to determine whether the microorganisms required a time interval to adapt to the new food source (test substance). Exposure to the test substance occurred at a concentration of 2 to 4 µL/300 ml. The control groups confirmed that the inoculum was active and the results indicated that adaptation was necessary in order for domestic sludge microorganisms to utilise the test substance as a substrate. Under the study conditions, 13% of test substance was removed in the first 15 d of the sampling period and 32% was degraded from 15 to 20 d. Under the study conditions, unadapted microorganisms therefore could not degrade the test substance within a 28 d period to a level allowing identification as readily biodegradable. Nevertheless, adapted microorganisms present where continuous exposure to the test substance occurs will readily remove the substance from sewage systems (Gezo, 1980).
QSAR model predictions (BioWin and BioHCwin):
The biodegradation potential of the test substance, p-methylstyrene, was estimated using the BioWin v4.11 program of EPI Suite v4.11. BIOWIN contains seven separate models.This version (v4.11) designates the models as Biowin1 (linear probability model), Biowin2 (nonlinear probability model), Biowin3 (expert survey ultimate biodegradation model), Biowin4 (expert survey primary biodegradation model), Biowin5 (MITI linear model), Biowin6 (MITI nonlinear model), Biowin7 (anaerobic biodegradation model). Using SMILES or CAS number as the input parameter, the biodegradability estimates are based upon fragment constants that were developed using multiple linear or non-linear regression analyses, depending upon the model. For p -methylstyrene, the Biowin 1 and Biowin 2 models both predicted 'biodegrades fast, Biowin3 and Biowin 4 predicted 'weeks' and 'days-weeks' respectively, Biowin 5 and Biowin 6 both predicted 'not readily biodegradable' (with probability of biodegradation as 0.36 and 0.387 respectively) and Biowin 7 predicted 'does not biodegrade fast'. As the criteria for overall 'yes' ready biodegradability prediction is based on the 'weeks' or faster and biodegradation probability of >=0.5 predictions by Biowin 3 and Biowin 5 respectively, the overall ready biodegradability prediction for the substance was 'No' (US EPA, 2018). The individual submodules (i.e., BioWin 2 and 3 or BioWin 3 and 6) however suggest that the substance do not meet the persistence criteria as per Annex XIII criteria as set out in the REACH Technical Guidance Document Chapter R.11 (Table R.11—4). The prediction for the substance is considered to be reliable, as it falls within of the applicability domain.
The biodegradation potential of the test substance, p-methylstyrene, was also estimated using the BioHCwin v1.01 program of EPI Suite v4.11.BioHCwin is a new predictive model within EPI Suite, which determines quantitative primary biodegradation half-lives of individual petroleum hydrocarbons. This model uses a fragment-based approach similar to BioWin.Using SMILES code as the input parameter the primary biodegradation half-life for the test substance was determined to be 3.897 d; indicating that the substance can be classed as readily biodegradable (US EPA, 2018). The prediction for the substance is considered to be reliable, as it falls within of the applicability domain.
Overall,in accordance with the restricted definition of readily biodegradable in screening tests used in the context of the REACH directive, the substance must be considered to be not readily biodegradable as preconditioning of the microorganisms is required as per the experimental study with the test substance. However, the individual submodule prediction from BioWin as well as half-life prediction from BioHCwin model of EPI Suite QSAR program, indicate that the substance is biodegradable and will not be persistent in the environment.
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