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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Study period:
2018-05-25
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Qualifier:
no guideline followed
Principles of method if other than guideline:
Ready Biodegradability model (IRFMN) (version 1.0.9)
QSAR classification model for Ready Biodegradability based on fragments built by SarPy software.
Developed by Politecnico di Milano, Italy and Istituto di Ricerche Farmacologiche Mario Negri, Italy.
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable
Conclusions:
Phenyl 4-hydroxybenzoate is estimated to be readily biodegradable by VEGA QSAR model.
Executive summary:

Prediction is Possible Readily Biodegradable, but the result may be not reliable. A check of the information given in the following section should be done, paying particular attention to the following issues:

- accuracy of prediction for similar molecules found in the training set is not optimal

- similar molecules found in the training set have experimental values that disagree with the predicted value

The following relevant fragments have been found: Possible RB alert no. 11  (benzoic acid); Possible RB alert no. 19  (anisole).

Endpoint:
biodegradation in water: screening test, other
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Remarks:
Data is from peer reviewed scientific paper
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Deviations:
not specified
GLP compliance:
no
Specific details on test material used for the study:
TEST MATERIAL
- Name: benzyl 4-hydroxybenzoate
- CAS: 94-18-8
- EC: 202-311-9
- Test material form: Solid
- Purity: > 98 %
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Tamiya river
- Water filtered: yes
- Type and size of filter used, if any: Filter through 3 µm pore size membrane filters.
Duration of test (contact time):
15 h
Initial conc.:
100 µg/L
Parameter followed for biodegradation estimation:
other: Half life of chemical
Details on study design:
TEST CONDITIONS
- Test temperature: 20°C
- Other: BOD of river water: 3.4 mg/L
TOC of river water: 2.4 mg/L

TEST SYSTEM
- Culturing apparatus: Flask

SAMPLING
- Sampling frequency: 1 time

CONTROL AND BLANK SYSTEM
- Inoculum blank: Milli Q water used as blank
Reference substance:
not specified
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
10 h
Remarks on result:
other: River water sampled in OCtober 2006
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
14 h
Remarks on result:
other: River water sampled in September 2007
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
19 h
Remarks on result:
other: river water sampled in November 2007
Key result
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
14.5 h
Remarks on result:
other: Mean of th three sampling times
Validity criteria fulfilled:
not applicable
Interpretation of results:
other: Moderately persistence
Conclusions:
Benzylparaben (CAS # 94-18-8) was having half lifes of 10 to 19 hrs which indicate that the substance is moderately persistence in water.
Executive summary:

The biodegradation of benzylparaben was tested in Tamiya river water. The test was conducted based on the OECD guideline 301A. The initial concentration of benzylparaben was 100 µg/L and the solution was placed in a flask at 20 °C. After experimenting it was found that the benzylparaben ( CAS # 94-18-8) was degraded to 50 % after 10 to 19 hrs which indicates that it is moderately persistence in water. Regarding the criteria for ready biodegradability (≥ 70 % DOC removal in 28 days) it can not be concluded from the paper if the substance fullfills this criterion, because in derivation from the guideline 100 µg a.i./L were used instead of 10 to 40 mg DOC/L. Also no information on control groups are reported.

Endpoint:
biodegradation in water: screening test, other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
The source compound Benzyl 4-hydroxybenzoate (EC 202-311-9, CAS 94-18-8) is considered a suitable read across partner for the target substance Phenyl 4-hydroxybenzoate (EC 241-698-9, CAS 17696-62-7). This read-across is based on the hypothesis that source and target substances have similar toxicological properties because:
- structural similarity of the target and the source substances (the presence or absence of additional functional groups or substituents that could influence the behaviour of a chemical),
- similarity in physico-chemical profile of the source and target substances (water solubility, partitioning behaviour (log Kow value))
Both substances are structural homologues regarding the functional groups at the ester (phenyl vs benzyl group). Both esthers have similar physico-chemical properties. Both are moderately/poorly water soluble (108 g/L vs 0.05 mg/L), exhibit similar log Kow values (3.97 vs 3.21), have similar boiling points (355 °C vs 241 °C) and vapour pressure (3.37x10-6 mm Hg vs 8.17x10-6 mm Hg).
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
10 h
Remarks on result:
other: River water sampled in OCtober 2006
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
14 h
Remarks on result:
other: River water sampled in September 2007
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
19 h
Remarks on result:
other: river water sampled in November 2007
Key result
Parameter:
% degradation (DOC removal)
Value:
50
Sampling time:
14.5 h
Remarks on result:
other: Mean of th three sampling times
Validity criteria fulfilled:
not applicable
Interpretation of results:
other: Moderately persistence
Conclusions:
Benzylparaben (CAS # 94-18-8) was having half lifes of 10 to 19 hrs which indicate that the substance is moderately persistence in water.
Executive summary:

The biodegradation of benzylparaben was tested in Tamiya river water. The test was conducted based on the OECD guideline 301A. The initial concentration of benzylparaben was 100 µg/L and the solution was placed in a flask at 20 °C. After experimenting it was found that the benzylparaben ( CAS # 94-18-8) was degraded to 50 % after 10 to 19 hrs which indicates that it is moderately persistence in water. Regarding the criteria for ready biodegradability (≥ 70 % DOC removal in 28 days) it can not be concluded from the paper if the substance fullfills this criterion, because in derivation from the guideline 100 µg a.i./L were used instead of 10 to 40 mg DOC/L. Also no information on control groups are reported.

This information is used in a read-across approach in the assessment of the target substance.

For details and justification of read-across please refer to the attached report in section 13 of IUCLID.

Description of key information

The substance is classified as readily biodegradable based on two QSAR models and one scientific publication.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

The biodegradability of phenylparaben is evaluated by one key study and two QSAR estimations. A scientific paper on the biodegradability on benzyl parabane in river water is available and used as read-across source. The experimental data were interpreted by the authors by characterizing the substance as moderately persistent. The 50 % degradation of the substance was reported after 10 to 19 hours and the reaction constant was determined with 0.10 to 0.069 per hour. But the experimental conditions deviate from the guideline regarding a.o. the initial concentration and the inoculum: 100 µg a.i./L were used instead of 10 to 40 mg DOC/L as recommended) and not activated sludge was used but river water. To comprehend the presented interpretation documentation is insufficient.

Therefore, two QSAR calculation were performed for further information on the biodegradability. The prediction from VEGA is: “Prediction is Possible Readily Biodegradable, but the result may be not reliable”, because the predicted compound is outside of the Applicability Domain of the model and similar molecules found in the training set have experimental values that disagree with the predicted value.

As second QSAR source (BioWin4) reports the substance as well as readily biodegradable.

Considering all available information the substance is rated as readily biodegradable.