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Environmental fate & pathways

Phototransformation in air

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phototransformation in air
Type of information:
Adequacy of study:
other information
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
no guideline followed
Principles of method if other than guideline:
Calculation using AOPWIN v1.92
GLP compliance:
Estimation method (if used):
- Concentration of OH radicals: 500000
- Degradation rate constant: XXX cm³/molecule-sec
- Temperature for which rate constant was calculated: 25 °C
- Computer programme: SRC AOP v1.92
- Calculated t 1/2 is based on a 24 h day
Key result
101.446 h
Test condition:
half-life calculated for the following conditions: sensitizer for indirect photolysis: OH; 0.5 E06 OH/cm³, 24h day; substance presumably within applicability domain

Estimate refers to the uncharged molecule.

Hydrogen Abstraction = 0.4909 E-12 cm3/molecule-sec

Reaction with N, S and -OH = 0.0000 E-12 cm3/molecule-sec

Addition to Triple Bonds = 0.0000 E-12 cm3/molecule-sec

Addition to Olefinic Bonds = 0.0000 E-12 cm3/molecule-sec

Addition to Aromatic Rings = 3.3048 E-12 cm3/molecule-sec

Addition to Fused Rings = 0.0000 E-12 cm3/molecule-sec

OVERALL OH Rate Constant = 3.7957 E-12 cm3/molecule-sec

HALF-LIFE = 4.227 Days (24-hr day; 0.5E6 OH/cm3)

HALF-LIFE = 101.446 Hrs

Validity criteria fulfilled:
not applicable
Executive summary:

1. Substance See "Test material identity
2.  General
2.1 Date of QPRF See “Data Source (Reference)”
2.2 QPRF author and
contact details
See “Data Source (Reference)”
3. Prediction
3.1 Endpoint
(OECD Principle 1)
Endpoint Phototransformation in air
Dependent variable Hydroxyl reaction rate
constant (cm3/molecule*sec)
3.2 Modul or submodel name AOPWIN
Model version 1.92
Reference to QMRF QMRF: Estimation of
Atmospheric Degradation Using AOPWIN v1.92 (EPI Suite v4.11): Hydroxyl Radical Reaction
Predicted value (modul result)  See “Results and discussion”
Input for prediction Chemical structure via
CAS number or SMILES
Descriptor values structure fragments
3.3 Algorithm
(OECD Principle 2)
Domain (On-Line AOPWIN User’s Guide):
As the complete training sets for AOPWIN's estimation methodology are not available, describing a precise estimation domain for this methodology is not possible. There is no information on the number of instances of fragments in the training dataset.
If the substance is a member of one of the following chemical classes, the substance is probably within the applicability domain of the model (based on information by other authors, e.g. Posthumus and Slooff, 2001):
alkanes, haloalkanes, alkenes, haloalkenes, polyenes, terpenes, alkynes, aldehydes, ketones, alcohols, glycols, ethers, esters, epoxides, thiols, thioethers, aliphatic amines, hydrazines, nitrites, nitrates, nitriles, P-containing organics, aromatic compounds (alkylbenzenes, halobenzenes, phenols, PAHs, styrene, methoxybenzene, aniline, nitrobenzene, biphenyl, dibenzofurans, dibenzodioxins)
The substance is not within the applicability domain of the model
if it is a perhalogenated alkanes.
Not fulfilled
Substance is a secondary, tertiary and heterocyclic amine. Estimated values highly uncertain. Not Fulfilled
3.4 The uncertainty of the prediction
(OECD principle 4)
- n = 667
-correlationcoefficient r2= 0.963
- standarddeviation= 0.218
- absolute mean error = 0.127
- 90% of the estimated rate constants within a factor of two of the experimental data
- 95% of the estimated rate constants within a factor of three of the experimental data
3.5 The chemical mechanisms according to the model underpinning the predicted result
(OECD principle 5)
Reaction rate constants for hydroxyl radicals are the summation of the following mechanisms:
(1) Hydrogen abstraction
(2) Reaction with specific nitrogen and sulphur fragments and reaction with hydroxyl (OH) fragments such as alcohols and phenols
(3) Addition to triple bonds
(4) Addition toolefinicbonds
(5) Addition to aromatic rings
(6) Addition to fused rings
The model works according to the group contribution method which uses fragments and the corresponding reaction values to estimate the reaction rate constant of a given substance.

References - Posthumus and Slooff(2001).Implementation of QSARs in ecotoxicological risk assessments.RIVM report 601516 003.Online:

- US EPA (2012).On-Line AOPWIN User’s Guide.

Description of key information

The half-life in air of the test substance was determined to be 101.446 hours.

Key value for chemical safety assessment

Half-life in air:
101.446 h
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information



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 phototransformation in air. 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 phototransformation in air are not provided.