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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
Data is from computational model developed by USEPA
Reference:
Composition 0
Qualifier:
according to
Guideline:
other: Modeling database
Principles of method if other than guideline:
The Biodegradation Probability Program (BIOWIN) estimates the probability for the rapid aerobic biodegradation of an organic chemical in the presence of mixed populations of environmental microorganisms .The model is part of the EpiSuite program of the US-EPA. Estimations are made with BIOWIN version 4.10. Estimates are based upon fragment constants that were developed using multiple linear and non-linear regression analyses. Experimental biodegradation data for the multiple linear and non-linear regressions were obtained from Syracuse Research Corporation's (SRC) data base of evaluated biodegradation data (Howard et. al., 1987). This version (v4.10) designates the models as follows (see also Boethling et al. 2003):
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
GLP compliance:
not specified
Test material information:
Composition 1
Specific details on test material used for the study:
Name of test material : 2-hydroxy-p-toluic acid
Molecular formula :C8H8O3
Molecular weight :152.148 g/mol
Smiles notation :Cc1ccc(c(c1)O)C(=O)O
InChl :1S/C8H8O3/c1-5-2-3-6(8(10)11)7(9)4-5/h2-4,9H,1H3,(H,10,11)
Substance Type: Organic
Physical State: White solid powder
Oxygen conditions:
other: aerobic (Biowin 1-6) and anaerobic (Biowin 7)
Inoculum or test system:
other: mixed populations of environmental microorganisms
Duration of test (contact time):
2.932 wk
Details on study design:
Using the computer tool BIOWIN v4.10 by US-EPA (EPIWIN) the aerobic as well as the anaerobic biodegradability of the test material can be estimated. The follwoing seven different models are used by the tool: Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI LInear Model, MITI Non-Linear Model and Anaerobic Model (calles Biowin 1-7, respectively). Due to this results the overall prediction of readily biodegradability is done for the desired chemical.

Biowin 1 and 2, are intended to convey a general indication of biodegradability under aerobic conditions, and not for any particular medium.
Biowin 1 (Linear model)
The fast biodegradation probability for any compound is calculated by summing, for all the fragments present in that compound, the fragment coefficient multiplied by the number of instances of the fragment in the compound (for MW, the value of that parameter is multiplied by its coefficient), and then adding this summation to the equation constant which is 0.7475. The summed values for each fragment coefficient multiplied by the number of instances appear in the "VALUE" column of the linear results screen.

Biowin 2 (Non-linear model)
Calculation of the fast biodegradation probability for any compound begins by summing, for all the fragments present in that compound, the fragment coefficient multiplied by the number of instances of the fragment in the compound (for MW, the value of that parameter is multiplied by its coefficient), then adding this summation to the equation constant which is 3.0087. The summed values for each fragment coefficient multiplied by the number of instances appear in the "VALUE" column of the non-linear results screen. The non-linear fast biodegradation probability is then calculated from the logistic equation as follows, where total = 3.0087 + the summation as described above:

Biowin 3 and 4 yield estimates for the time required to achieve complete ultimate and primary biodegradation in a typical or "evaluative" aquatic environment.

Biowin 5 and 6 are predictive models for assessing a compound’s biodegradability in the Japanese MITI (Ministry of International Trade and Industry) ready biodegradation test; i.e. OECD 301C. These models use an approach similar to that used to develop Biowin1 and 2. This protocol for determining ready biodegradability is among six officially approved as ready biodegradability test guidelines of the OECD (Organization for Economic Cooperation and Development). A total dataset of 884 chemicals was compiled to derive the fragment probability values that are applied in this MITI Biodegradability method. The dataset consists of 385 chemical that were critically evaluated as "readily degradable" and 499 chemicals that were critically evaluated as "not readily biodegradable".

Biowin 7, the anaerobic biodegradation model, is the most recent. As for the other Biowin models, multiple (linear) regression against molecular fragments was used to develop the model, which predicts probability of rapid degradation in the "serum bottle" anaerobic biodegradation screening test. This endpoint is assumed to be predictive of degradation in a typical anaerobic digester. Biowin7 estimates the probability of fast biodegradation under methanogenic anaerobic conditions; specifically, under the conditions of the "serum bottle" anaerobic biodegradation screening test (Meylan et al. 2007). A total of 169 compounds with serum bottle test data were identified for use in model development.

Out of seven different Biowin models, Biowin model 3 and 4 will help in estimating biodgeradability of the test chemical which was described as below-

Ultimate Biodegradation Timeframe and Primary Biodegradation Timeframe (Biowin 3 and 4)
These two models estimate the time required for "complete" ultimate and primary biodegradation.  Primary biodegradation is the transformation of a parent compound to an initial metabolite.  Ultimate biodegradation is the transformation of a parent compound to carbon dioxide and water, mineral oxides of any other elements present in the test compound, and new cell material. Then the rating was given to each model, which indicates the time required to achieve ultimate and primary biodegradation in a typical or "evaluative" aquatic environment. The ratings for each compound were averaged to obtain a single value for modeling.  The ultimate or primary rating of a compound is calculated by summing, for all the fragments present in that compound.
Key result
Parameter:
other: Half life
Value:
50
Sampling time:
2.932 wk
Remarks on result:
other: readily biodegradable as estimated by BIOWIN model
Details on results:
Biowin1 (Linear Model Prediction) : Biodegrades Fast
Biowin2 (Non-Linear Model Prediction): Biodegrades Fast
Biowin3 (Ultimate Biodegradation Timeframe): Weeks
Biowin4 (Primary Biodegradation Timeframe): Days-Weeks
Biowin5 (MITI Linear Model Prediction) : Biodegrades Fast
Biowin6 (MITI Non-Linear Model Prediction): Biodegrades Fast
Biowin7 (Anaerobic Model Prediction): Biodegrades Fast
Ready Biodegradability Prediction: YES

BIOWIN (v4.10) Program Results:

==============================

SMILES : Cc1ccc(C(=O)(O))c(O)c1

CHEM : Benzoic acid, 2-hydroxy-4-methyl-

MOL FOR: C8 H8 O3

MOL WT : 152.15

--------------------------- BIOWIN v4.10 Results ----------------------------

Biowin1 (Linear Model Prediction) : Biodegrades Fast

Biowin2 (Non-Linear Model Prediction): Biodegrades Fast

Biowin3 (Ultimate Biodegradation Timeframe): Weeks

Biowin4 (Primary Biodegradation Timeframe): Days-Weeks

Biowin5 (MITI Linear Model Prediction) : Biodegrades Fast

Biowin6 (MITI Non-Linear Model Prediction): Biodegrades Fast

Biowin7 (Anaerobic Model Prediction): Biodegrades Fast

Ready Biodegradability Prediction: YES

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin1 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.1158 | 0.1158

Frag | 1 | Aromatic acid [-C(=O)-OH] | 0.1769 | 0.1769

Frag | 1 | Alkyl substituent on aromatic ring | 0.0547 | 0.0547

MolWt| * | Molecular Weight Parameter | | -0.0724

Const| * | Equation Constant | | 0.7475

============+============================================+=========+=========

RESULT | Biowin1 (Linear Biodeg Probability) | | 1.0225

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin2 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.9086 | 0.9086

Frag | 1 | Aromatic acid [-C(=O)-OH] | 2.4224 | 2.4224

Frag | 1 | Alkyl substituent on aromatic ring | 0.5771 | 0.5771

MolWt| * | Molecular Weight Parameter | | -2.1605

============+============================================+=========+=========

RESULT | Biowin2 (Non-Linear Biodeg Probability) | | 0.9915

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin3 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.0564 | 0.0564

Frag | 1 | Aromatic acid [-C(=O)-OH] | 0.0879 | 0.0879

Frag | 1 | Alkyl substituent on aromatic ring | -0.0749 | -0.0749

MolWt| * | Molecular Weight Parameter | | -0.3362

Const| * | Equation Constant | | 3.1992

============+============================================+=========+=========

RESULT | Biowin3 (Survey Model - Ultimate Biodeg) | | 2.9323

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin4 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.0397 | 0.0397

Frag | 1 | Aromatic acid [-C(=O)-OH] | 0.0077 | 0.0077

Frag | 1 | Alkyl substituent on aromatic ring | -0.0685 | -0.0685

MolWt| * | Molecular Weight Parameter | | -0.2195

Const| * | Equation Constant | | 3.8477

============+============================================+=========+=========

RESULT | Biowin4 (Survey Model - Primary Biodeg) | | 3.6071

============+============================================+=========+=========

Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks

6

(Primary & Ultimate) 2.00 -> months 1.00 -> longer

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin5 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.0642 | 0.0642

Frag | 1 | Aromatic acid [-C(=O)-OH] | 0.3770 | 0.3770

Frag | 1 | Aromatic-CH3 | 0.0415 | 0.0415

Frag | 3 | Aromatic-H | 0.0082 | 0.0247

MolWt| * | Molecular Weight Parameter | | -0.4526

Const| * | Equation Constant | | 0.7121

============+============================================+=========+=========

RESULT | Biowin5 (MITI Linear Biodeg Probability) | | 0.7668

============+============================================+=========+=========

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin6 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.4884 | 0.4884

Frag | 1 | Aromatic acid [-C(=O)-OH] | 2.4449 | 2.4449

Frag | 1 | Aromatic-CH3 | 0.3072 | 0.3072

Frag | 3 | Aromatic-H | 0.1201 | 0.3604

MolWt| * | Molecular Weight Parameter | | -4.3924

============+============================================+=========+=========

RESULT |Biowin6 (MITI Non-Linear Biodeg Probability)| | 0.8500

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable

A Probability Less Than 0.5 indicates --> NOT Readily Degradable

------+-----+--------------------------------------------+---------+---------

TYPE | NUM | Biowin7 FRAGMENT DESCRIPTION | COEFF | VALUE

------+-----+--------------------------------------------+---------+---------

Frag | 1 | Aromatic alcohol [-OH] | 0.0807 | 0.0807

Frag | 1 | Aromatic acid [-C(=O)-OH] | 0.2656 | 0.2656

Frag | 1 | Alkyl substituent on aromatic ring | -0.1145 | -0.1145

Frag | 1 | Aromatic-CH3 | -0.2573 | -0.2573

Frag | 3 | Aromatic-H | -0.0954 | -0.2863

Const| * | Equation Constant | | 0.8361

============+============================================+=========+=========

RESULT | Biowin7 (Anaerobic Linear Biodeg Prob) | | 0.5243

============+============================================+=========+=========

A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast

A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Ready Biodegradability Prediction: (YES or NO)

----------------------------------------------

Criteria for the YES or NO prediction: If the Biowin3 (ultimate survey

model) result is "weeks" or faster (i.e. "days", "days to weeks", or

"weeks" AND the Biowin5 (MITI linear model) probability is >= 0.5, then

the prediction is YES (readily biodegradable). If this condition is not

satisfied, the prediction is NO (not readily biodegradable). This method

is based on application of Bayesian analysis to ready biodegradation data

(see Help). Biowin5 and 6 also predict ready biodegradability, but for

degradation in the OECD301C test only; using data from the Chemicals

Evaluation and Research Institute Japan (CERIJ) database.

Validity criteria fulfilled:
not specified
Interpretation of results:
other: readily / not readily biodegradable.
Conclusions:
The biodegradability of the substance 2-hydroxy-p-toluic acid was calculated using seven different Biowin 1-7 models of the BIOWIN v4.10 software. The results indicate that the test chemical 2-hydroxy-p-toluic acid is expected to be readily biodegradable.
Executive summary:

Estimation Programs Interface Suite (EPI suite, 2017) was run to predict the biodegradation potential of the test compound   2-hydroxy-p-toluic acid (CAS no. 50 -85 -1) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical  2-hydroxy-p-toluic acid is expected to be readily biodegradable.

Description of key information

Estimation Programs Interface Suite (EPI suite, 2017) was run to predict the biodegradation potential of the test compound 2-hydroxy-p-toluic acid (CAS no. 50 -85 -1) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical 2-hydroxy-p-toluic acid is expected to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One predicted data study and one experimental study for target chemical and five experimental studies for its structurally similar read across chemical have been conducted for biodegradation in water endpoint and results of all the studies are summarized below.

The predicted data study for target chemical was done by using Estimation Programs Interface Suite (EPI suite, 2017) to estimate the biodegradation potential of the test compound 2-hydroxy-p-toluic acid (CAS no. 50 -85 -1) in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical 2-hydroxy-p-toluic acid is expected to be readily biodegradable.

Another study was experimental study done from peer reviewed journal Applied and Environmental Microbiology, (Kathleen L. Londry et. al; 1997) and secondary source (Kathleen Louise Londry, 1997) in this study biodegradation experiment was conducted for evaluating the percentage biodegradability of test substance 2-Hydroxy-4-methylbenzoic acid (CAS no. 50-85-1) under anaerobic conditions at a temperature of 32°C .Desulfotomaculumsp. strain Groll (bacteria) was used as a test inoculum obtained from the Deutsche Sammlung von Mikroorganismen, Braunschweig, Germany (catalog no. 7213). Initial test substance conc. used in the study was 76.07 mg/l (500µM).The organism was cultivated in an anaerobic medium but with only 1 mM sulfide as the reductant. Strain Groll was incubated at 32°C in the dark without shaking. Cultures were maintained by periodically adding substrate (250mM) and by repeated transfer. The cultures were amended by addition of substrates from neutralized, sterile, anoxic stock solutions. Test was performed in an anaerobic chamber which was sealed with butyl rubber stoppers and aluminum crimp seals. The headspace of each vessel was then changed to N2-CO2 (80 : 20). The degradation of test substance was tested in the anaerobic medium and inoculated (10% vol/vol) with a culture of strain Groll. Degradation was monitored by following the depletion of test compound over time. Sterile controls were also setup during the study. Samples of culture fluid were withdrawn under strictly anaerobic and aseptic conditions and stored frozen until analyzed. Concentrations of test compound 2 -Hydroxy-4 -methylbenzoic acid were determined by HPLC. The percentage degradation of test substance 2 -Hydroxy-4 -methylbenzoic acid was determined to be 0% by HPLC parameter. Thus, based on percentage degradation, 2 -Hydroxy-4 -methylbenzoic acid is considered to be not readily biodegradable in nature.

Next experimental study was done for read across chemical salicylic acid (CAS no. 69-72-7) from Journal of Hazardous Materials (1986) in this study the biodegradability of read across chemical salicylic acid was determined, by using electrolytic respirometer in aerobic condition. The study was calculated for 14 days, at temperature 20 °C in neutral medium (pH-7).The biodegradability of read across chemical salicylic acid was calculated, as the 50% of salicylic acid was biodegrades in 7.5 to 9.5 hrs only. Result indicated that the read across chemical salicylic acid is readily biodegradable in water.

 

Another experimental study was done from authoritative database (J check, 2016) in this study biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance Aspirin (CAS no. 50-78-2). Concentration of inoculum i.e, sludge used was 30 mg/l and initial read across substance conc. used in the study was 100 mg/l, respectively. At the beginning of the test, the pH of the test solution was adjusted. The read across substance was hydrolyzed to form Salicylic acid and Acetic acid in (Water + Test Substance) systems. The percentage degradation of read across substance was determined to 86%, 97% and 100% by BOD, TOC removal and HPLC parameter in 28 days. Thus, based on percentage degradation, Aspirin is considered to be readily biodegradable in nature.

Next experimental study was done for read across substance 2-methoxybenzoic acid (CAS no. 579-75-9) from Environmental Toxicology and Chemistry journal (2003) in this study biodegradation experiment was conducted for 5 days for evaluating the percentage biodegradability of read across substance 2-methoxybenzoic acid(CAS no. 579-75-9).The study was performed using the standard iodometric titration method. River water was used as a test inoculum obtained from Jilin section in the Songhua river. Temperature of the water sample was 15-20°C, pH 6.8 – 7.0 and dissolved oxygen was ranged between 7.8 – 9.0 mg/l. Initial read across substance conc. used in the study was 2 mg/l on the basis of ThOD. The test chemical was added to 250 ml BOD bottles. One milliliter of diluted water sample was cultivated in 15 ml of medium at 31°C for 24 h, and the number of colonies was enumerated as the bacterial counts. The bottles were then filled to capacity with the water sample, sealed and incubated for 5 days at 20 ± 1°C.Two replicates were conducted for read across chemical and read across control (inoculum only).The DO concentrations were determined by the iodometric titration method. Biodegradability was assessed by measuring the BOD values in milligrams per liter (oxygen uptake values of test compound minus control).Biodegradability was expressed as the first-order kinetic rate constant (K) according to the traditional Monod equation (on the assumption that the bacterial counts were invariable during the experimental period).The total surface area of molecules, the heat of formation (Hf), and the energy of the highest occupied molecular orbital (EHOMO) of read across chemical was calculated by the quantum chemical method Mopac Program. The linear regression analyses were performed with the SPSS® statistical package (Ver 10.0, SPSS, Chicago, IL, USA).An obvious negative correlation apparently exists between Hf and K, that is, the lower the Hf value (-422.08 kj/M), the higher the K value (1.06/d), and thus based on this relationship, read across chemical was considered to be readily biodegradable by river bacteria.

Next study was done from peer reviewed journal “The Science of the Total Environment,” (1995) in this study Biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance Benzoic acid by bacteria as a test inoculum. Seeding bacteria was used as a test inoculum. The seeding bacteria had been cultured in a continuous anaerobic bioreactor at 37 + 1°C. Synthetic sewage, composed of glucose, peptone and corn steap liquor (carbon ratio = 1:1:2), is supplied into the reactor (3.0 g-C/l, 8.0 g-CS./.d). In this culture, > 95% acidic decomposition and > 90% methanogenic decomposition are achieved. A standard test using 50 ml vials (total capacity: 68 ml) was employed. Ten test vials were prepared under the same conditions, and they were set in a water bath at 37°C ± 0.5”C. The original solution was added to the test inoculum and organic medium in oxygen-free water. At the starting time and after every week, two vials were opened simultaneously, and the concentration of organic compound was analyzed. The concentration of organic compound was determined by dissolved organic carbon (DOC).Biodegradation ratio is determined by analyzing the decrease of DOC in the standard test. The percentage degradation of the read across compound was determined to be 101% in 14 days by using standard test. Thus, based on the percentage degradation, the read across chemical Benzoic acid (CAS no.65-85-0) was considered to be readily biodegradable in nature.

Last experimental study was done from Water Pollution Control Federation journal (1976) in this study , Biodegradation experiment was conducted for 30 days for evaluating the percentage biodegradability of read across substance 1,2-Benzenedicarboxylic acid, monopotassium salt (CAS no.877-24-7) . Glucose-glutamic acid mixture was used as a reference substance for the biodegradation study. The results are compared with the chemical oxygen demand (COD) of the read across chemical, which measures its maximum oxygen combining power; the results are also compared with the BOD test performed on a standard glucose-glutamic acid reference solution used for BOD calibration. Reference substance i.e; glucose-glutamic acid mixture consumes 75 percent of its maximum oxygen requirement (COD) within 5 days and almost 100 percent in 30 days. Thus, based on this result, the reference substance is considered to be readily biodegradable. The percentage degradation of read across substance was determined to be 92% by BOD parameter in 30 days. Thus, based on percentage degradation, read across chemical 1,2-Benzenedicarboxylic acid, monopotassium salt was considered to be readily biodegradable in nature.

Thus by considering all the studies mentioned above for target chemical 2-hydroxy-p-toluic acid (CAS no. 50 -85 -1) and its various structurally similar read across chemicals it is observed that predicted data study for target chemical interpret that target chemical is readily degradable but experimental study shows that it is not readily degradable but this result is obtained by using bacteria Desulfotomaculumsp. strain Groll and this bacteria is Gram positive anaerobic bacteria and uses sulfate as terminal electron acceptor which is reduced to sulfide. It is generally found in subsurface biosphere 10-100M below ground or sea bed. Therefore maybe because of all this criteria of this bacteria test chemical is not degraded by using this bacteria and this experiment was also conducted in anerobic condition. It can be possible that target chemical is readily degradable by aerobic condition by different bacteria. This possibility of degradation is supported by various studies of structurally similar read across chemicals as mentioned above from different sources all studies of read across chemical are showing that it is readily degradable. Further according to OECD guidelines degradability of target chemical should be analyzed by using activated sludge or bacteria from soil or water which are easily available in nature and has many different types of bacteria. Therefore on the basis of predicted data of target chemical and its structurally similar read across chemicals it is concluded that target chemical is readily biodegradable in nature.