α-chloro-o-xylene

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Version / remarks:

January 1986

Deviations:

not specified

Qualifier:

according to guideline

Guideline:

other: DIN 38.412, Teil 25: Bestimmung der biologischen Abbaubarkeit, statischer Test

Version / remarks:

January 1984

Deviations:

not specified

GLP compliance:

not specified

Specific details on test material used for the study:

Not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial (adaptation not specified)

Details on inoculum:

- Source of Inoculum: Activated sludge from an industrial sewage treatment plant at Höchst factory, HOECHST AG
- Inoculum Concentration in Stock Solutions: 1.1 +/- 0.1 g/L dry substance

Duration of test (contact time):

9 d

Initial conc.:

>= 50 - <= 400 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

not specified

Reference substance:

not specified

Preliminary study:

Not specified

Test performance:

Not specified

Key result

Parameter:

% degradation (O2 consumption)

Value:

95

Sampling time:

9 d

Results with reference substance:

Not specified

Validity criteria fulfilled:

not specified

Interpretation of results:

readily biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

key 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

Principles of method if other than guideline:

The model is based on the OECD TG 301C - modified MITI -I test data and provides a qualitative evaluation (binary classification) of ready biodegradability properties.
The applicability domain of predictions is assessed using an Applicability Domain Index (ADI) that has values from 0 (worst case) to 1 (best case). The ADI is calculated by grouping several other indices, each one taking into account a particular issue of the applicability domain. Most of the indices are based on the calculation of the most similar compounds found in the training and test set of the model, calculated by a similarity index that consider molecule's fingerprint and structural aspects (count of atoms, rings and relevant fragments).

Remarks on result:

other: Ready biodegradability prediction: The compound is classified as possible ready biodegradable

Remarks on result:

other: According to the model's global AD index, the predicted substance could be out of the Applicability Domain.

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Executive summary:

Biodegradation – The Ready Biodegradability model v1.0.8 implemented in the VEGA platform v1.0.8:Estimation Domain (QPRF)

 

The applicability domain of predictions is assessed using an Applicability Domain Index (ADI) that has values from 0 (worst case) to 1 (best case). The ADI is calculated by grouping several other indices, each one taking into account a particular issue of the applicability domain. Most of the indices are based on the calculation of the most similar compounds found in the training and test set of the model, calculated by a similarity index that consider molecule's fingerprint and structural aspects (count of atoms, rings and relevant fragments).

 

For each index, including the final ADI, three intervals for its values are defined, such that the first interval corresponds to a positive evaluation, the second one corresponds to a suspicious evaluation and the last one corresponds to a negative evaluation.

 

Following, all applicability domain components are reported along with their explanation and the intervals used. Furthermore, the specific index of the substance is given. Note that for purpose of evaluating accuracy and concordance indices, prediction of "possible ready biodegradable" and "possible non ready biodegradable" are considered as "ready biodegradable" and "non ready biodegradable".

 

 

-Similar molecules with known experimental value.

This index takes into account how similar are the first two most similar compounds found. Values near 1 mean that the predicted compound is well represented in the dataset used to build the model, otherwise the prediction could be an extrapolation.

 

Defined intervals are:

1 >= index > 0.85	strongly similar compounds with known experimental value in the training set have been found
0.85 >= index > 0.7	only moderately similar compounds with known experimental value in the training set have been found
index <= 0.7	no similar compounds with known experimental value in the training set have been found

 

The subsatnce has a similarity index of 0.906.

 

 

-Accuracy of prediction for similar molecules.

This index takes into account the error in prediction for the three most similar compounds found. Values near 0 mean that the predicted compounds falls in an area of the model's space where the model gives reliable predictions, otherwise the greater is the value, the worse the model behaves.

 

Defined intervals are:

1 >= index > 0.8	accuracy of prediction for similar molecules found in the training set is good
0.8 >= index > 0.5	accuracy of prediction for similar molecules found in the training set is not optimal
index < 0.5	accuracy of prediction for similar molecules found in the training set is not adequate

 

 The substance has an accuracy index of 1.

 

-Concordance for similar molecules.

This index takes into account the difference between the predicted value and the experimental values of the three most similar compounds. Values near 0 mean that the prediction made disagrees with the values found in the model's space, thus the prediction could be unreliable.

 

Defined intervals are:

1 >= index > 0.8	similar molecules found in the training set have experimental values that agree with the target compound predicted value
0.8 >= index > 0.5	some similar molecules found in the training set have experimental values that disagree with the target compound predicted value
index <= 0.5	similar molecules found in the training set have experimental values that disagree with the target compound predicted value

 

The substance has a conccordance index of 0.673 .

 

-Atom Centered Fragments similarity check.

This index takes into account the presence of one or more fragments that aren't found in the training set, or that are rare fragments. First order atom centered fragments from all molecules in the training set are calculated, then compared with the first order atom centered fragments from the predicted compound; then the index is calculated as following: a first index RARE takes into account rare fragments (those who occur less than three times in the training set), having value of 1 if no such fragments are found, 0.85 if up to 2 fragments are found, 0.7 if more than 2 fragments are found; a second index NOTFOUND takes into account not found fragments, having value of 1 if no such fragments are found, 0.6 if a fragments is found, 0.4 if more than 1 fragment is found. Then, the final index is given as the product RARE * NOTFOUND.

 

Defined intervals are:

index = 1	all atom centered fragment of the compound have been found in the compounds of the training set
1 > index >= 0.7	some atom centered fragment of the compound have not been found in the compounds of the training set or are rare fragments
index < 0.7	a prominent number of atom centered fragments of the compound have not been found in the compounds of the training set or are rare fragments

 

The substance has an ACF matching index of 0.85. 

-Global AD Index.

The final global index takes into account all the previous indices, in order to give a general global assessment on the applicability domain for the predicted compound.

 

Defined intervals are:

1 >= index >= 0.8	predicted substance is into the Applicability Domain of the model
0.8 > index >= 0.65	predicted substance could be out of the Applicability Domain of the model
index < 0.65	predicted substance is out of the Applicability Domain of the model

 

The substance has a global AD index of 0.733. 

 

References:

VEGA Guide to Ready Biodegradability Model version 1.0.8 implemented in the VEGA tool v1.0.8

 

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

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

Principles of method if other than guideline:

OASIS CATALOGIC Kinetic 301F v.13.16 (June 2016)

GLP compliance:

no

Parameter:

half-life in days (QSAR/QSPR)

Value:

11.79

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Parameter:

half-life in days (QSAR/QSPR)

Remarks:

Ultimate Half Life

Value:

17.74

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Parameter:

% degradation (O2 consumption)

Value:

>= 0.461 - <= 0.879

Sampling time:

28 d

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Description of key information

The test substance is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Discussion

The inherent biodegradability of the test substance was investigated in an respirometric test according to the OECD guideline 302 B and DIN 38412 (L12) (Wellens, 1990). The biodegradation of the test substance was followed by exposure to microorganisms from an industrial sewage treatment plant. The inoculum concentration in the stock solutions was 1.1 ± 0.1 g/L dry substance.The test item concentration selected as appropriate corresponded to an DOC concentration of 50 -400 mg/L. In result, after 9 days a biodegradation rate of 95 % was already reached. The acclimation phase was about 3 days and the logarithmic phase was about 4 days (70% of test duration). Based on the very high degradation rate passing the threshold value for inherent biodegradability of 70% degradation after less than 9 days, the test item is considered to be readily biodegradable.

This result is supported by QSAR predictions with VEGA v1.0.8 Ready Biodegradability model v1.0.9 and OASIS CATALOGIC Kinetic 301F v.13.16, since the test item was determined as readily biodegradable by these models, too.

Overall Conclusion

In conclusion, the test substance is regarded as readily biodegradable.

QSAR Disclaimer

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

For the assessment of 2 -Methylbenzylchloride(Q)SAR results were used for aerobic biodegradability in water.The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

 

Therefore, further experimental studies on aerobic biodegradability in water are not provided.