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Diss Factsheets

Administrative data

Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2022
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

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Unnamed
Year:
1993
Reference Type:
publication
Title:
Kinetics and mechanisms of the gas-phase reactions of the hydroxyl radical with organic compounds
Author:
Atkinson R
Year:
1989
Bibliographic source:
J Chem Phys Ref Data Monographs 1, 103.
Reference Type:
publication
Title:
Unnamed
Year:
1988
Reference Type:
other: computer program
Title:
Unnamed
Year:
2010
Reference Type:
other: Computer QSAR model
Title:
Episuite V 4.11
Author:
US EPA
Year:
2021
Bibliographic source:
EPA
Report date:
2021

Materials and methods

Principles of method if other than guideline:
Software tool(s) used including version: EPISuite v4.10
Model(s) used: Aopwin v1.92a
Model description: see field 'Attached justification'

Test material

Constituent 1
Chemical structure
Reference substance name:
1,2-Benzenedicarboxylic acid, di-C9-11-branched alkyl esters, C10-rich
EC Number:
271-091-4
EC Name:
1,2-Benzenedicarboxylic acid, di-C9-11-branched alkyl esters, C10-rich
Cas Number:
68515-49-1
Molecular formula:
C28 H46 O4
IUPAC Name:
1,2-Benzenedicarboxylic acid, di-C9-11-branched alkyl esters, C10 rich
Constituent 2
Reference substance name:
1,2-benzenedicarboxylic acid, di-C9,C10 and C11 branched alkyl ester, C10 Rich
IUPAC Name:
1,2-benzenedicarboxylic acid, di-C9,C10 and C11 branched alkyl ester, C10 Rich
Details on test material:
SMILES notation used: O=C(c1ccccc1C(=O)OCCCCCCCC(C)C)OCCCCCCCC(C)C

Study design

Light source:
sunlight
Details on test conditions:
Temperature: 25°C.
Sensitizer: OH radical.
Concentration of Sensitizer: 1.5 E6 OH radicals/cm3.

Results and discussion

Dissipation half-life of parent compound
DT50:
>= 4.3 - <= 5.2 h
Test condition:
Estimated value
Transformation products:
not specified

Any other information on results incl. tables

In the environment, organic chemicals emitted into the troposphere are degraded by several important transformation processes. The dominant transformation process for most compounds is the daylight reaction with hydroxyl (OH-) radicals (Atkinson, 1988, 1989). The rate at which an organic compound reacts with OH- radicals is a direct measure of its atmospheric persistence (Meylan and Howard, 1993). AOPWIN estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals.  The rate constants estimated by the program are then used to calculate atmospheric half-lives for organic compounds based upon average atmospheric concentrations of hydroxyl radicals. Since the reactions only take place in the presence of sunlight, the atmospheric half-lives are normalized for a 12-hour day.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The photodegradation half-life as mediated by OH- attack is estimated as 0.355 to 0.434 days or 4.3 to 5.2 hours based on a 12-hour sunlight day, a degradation rate of 30.1645 E-12 to 24.6469 E-12 cm³/molecule*sec, and an average OH-concentration of 1.5E6 OH-/cm3.
Executive summary:

Indirect photochemical degradation of DIDP as mediated by OH- attack is estimated to have a half-life <0.43 days or 5.2 hours based on a 12-hour sunlight day, a rate <24.6E-12 cm3/molecule*sec, and an average OH- concentration of 1.5E6 OH-/cm3. A 12-hour day half-life value normalizes degradation to a standard day light period during which hydroxyl radicals needed for photolysis are generated in the atmosphere. Although DIDP has the potential to degrade rapidly by OH- attack, multimedia distribution modeling indicates DIDP is predicted to partition negligibly (0.1%) to the air compartment because it has a low vapor pressure (0.000051 Pa). Although DIDP has a relatively short atmospheric oxidation half-life (<5.2 hours), this process is unlikely to contribute significantly to the loss of DIDP from the environment.