Registration Dossier

Administrative data

Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
28-May-2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Structurally, MeDONA contains moieties that have experimental group rate constants utilized by the software (AOPWIN) to calculate the OH radical reaction rate constants. Comparative evaluation of predicted and experimental values of analogous compounds (fluorinated ethers, fluorinated carboxylic acid esters and fluorinated alkyls) in the training set indicate that MeDONA is within the domain of the AOPWIN model.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6

Data source

Reference
Reference Type:
other company data
Title:
Unnamed
Year:
2013
Report date:
2013

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: QSAR results
Deviations:
no
Principles of method if other than guideline:
AOPWIN v1.92 as implemented through EPI Suite v4.11
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
MeDONA
IUPAC Name:
MeDONA

Study design

Estimation method (if used):
EPISuite (v4.11) module AOPWIN (v1.92) utilizes experimentally determined group rate constants to estimate the overall OH radical reaction rate constant for a chemical. EPISuite is a valid QSAR and this substance is within the applicability domain since there are analogous substances in the training set.
Light source:
other: Not Applicable (QSAR)
Details on light source:
Not Applicable (QSAR)
Details on test conditions:
QSAR

Results and discussion

Dissipation half-life of parent compound
DT50:
147 d
Test condition:
QSAR simulation. hydroxyl radical rate constant = 1.095E-13 cm³ molecule-1 s-1, 5E+05 OH/cm³, 24-hour day (photoperiod).

Any other information on results incl. tables

Validity of Model (OECD 5 principles):

1) Defined endpoint: Photodegradation rate

2) Unambiguous algorithm: The predicted value of the rate constant for reaction with hydroxyl radicals is calculated through the following equation: overall OH rate const = ∑F(x)k{group} where F(x) is the substituent scale factor and k{group} is the hydroxyl radical reaction rate constant for each individual chemical group in the test species.

3) Applicability domain: the software's training set contains several fluorinated alkyl ethers, fluorinated alkyls, and a fluorinated carboxylic acid ester which are structurally related to the test substance. This is not an exhaustive list of all chemical species in the reference data, merely those which may be grouped with the test compound to evaluate the applicability domain. Comparative evaluation of predicted and experimental values of the analogous compounds in the training set indicate that MeDONA is within the domain of the AOPWIN model.

4) Statistical characterization: Statistical variation of 20 pairs of experimental and predicted photodegradation rates for fluorinated alkyl ethers, fluorinated alkyls, and a fluorinated carboxylic acid ester indicate that there is a 0.816 correlation coefficient (r-squared), a standard deviation of 0.279 and an absolute mean error of 0.229.

5) Mechanistic interpretation: The primary mechanism of photolysis is through indirect photodegradation by reaction with hydroxyl radicals which are produced during the daylight hours. Please see attached QMRF and QPRF for justification of model and applicability.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
This model conforms with the 5 principles set forth by OECD for validation of QSAR models.
Conclusions:
The half-life of MeDONA, based on hydroxyl radical concentrations in the atmosphere of 5.0E+05 OH radicals / cm3 per 24-hour day, is estimated to be 147 days. This indicates that degradation through indirect photolysis is very slow and long range transport is expected.
Executive summary:

Photolysis of MeDONA was estimated utilizing the AOPWIN v1.92 module of EPISuite v4.11.  Structurally, MeDONA contains moieties that are part of the training set of the software and is thus, within the predictive domain of the software. The half-life/DT50 (50% decline times) of the test substance, using hydroxyl radical concentrations in the atmosphere of 5.0E+05 OH radicals / cm3 per 24 hr day, was predicted to be 147 days. This indicates that the test material is expected to be very persistent in the atmosphere and long range transport is expected.   This study is classified as an acceptable QSAR and satisfies the requirements for photolysis study. It is pertinent to the fate of MeDONA and is suitable for use in Risk Assessment, Classification & Labeling, and PBT Analysis.