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Environmental fate & pathways

Phototransformation in air

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Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
January 31, 2012
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Estimation method using accepted and valid (Q)SAR method.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Guideline:
other: ECHA Guidance on information requirements and chemical safety assessment - Chapter R.06: QSARs and grouping of chemicals - May2008
Principles of method if other than guideline:
The Atmospheric Oxidation Program for Microsoft Windows (AOPWIN) estimates the rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals.  It also estimates the rate constant for the gas-phase reaction between ozone and olefinic/acetylenic compounds. 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 and ozone.
The estimation methods used by AOPWIN are based upon the structure-activity relationship (SAR) methods developed by Dr. Roger Atkinson and co-workers (Atkinson, 1985, 1986, 1987, 1991; Atkinson and Carter, 1984; Biermann et al, 1985; Kwok et al, 1992, Kwok and Atkinson, 1995; Kwok et al, 1996).
AOPWIN incorporates updated fragment and reaction values as cited in Kwok and Atkinson (1995).  In addition, Syracuse Research Corporation has derived some additional fragment and reaction values from new experimental data. A journal article that discusses the Atmospheric Oxidation Program has been published (Meylan and Howard, 1993).
AOPWIN requires only a chemical structure to make these predictions.
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 1.5E+06 OH radicals/cm3; Half-life: 12 h/day
- Concentration of OH radicals: 0.5E+06 OH radicals/cm3; Half-life: 24 h/day
- Degradation rate constant: 0.00000265 cm³ molecule-1 d-1
- Temperature for which rate constant was calculated: 25 deg C
- Computer programme: EPIWIN v.4.1, part AOPWIN v.1.92. (2011)
DT50:
12.5 h
Test condition:
OH concentration: 0.5E+06 OH radicals/cm3; Half-life: 24 h/day (EU std. conditions)
DT50:
4.2 h
Test condition:
OH concentration: 1.5E+06 OH radicals/cm3; Half-life: 12 h/day (USA std. conditions)
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1

Compound Being Estimated:

SMILES:O=C(OCCCCCCCC)c1cc(ccc1C(=O)OCCCCCCCC)C(=O)OCCCCCCCC

CHEM:trioctyl benzene-1,2,4-tricarboxylate

MOL FOR: C33 H54 O6

MOL WT: 546.79

European settings

OH radical concentration: 0.5E+06 OH radicals/cm3Half-life: 24 h/day

---------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) ----------

 

Hydrogen Abstraction=  30.6584 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= 0.0461 E-12 cm3/molecule-sec

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

 

 OVERALL OH Rate Constant = 30.7044 E-12 cm3/molecule-sec= 2.65 E-06 cm3/molecule-day

 

  HALF-LIFE= 0.523 Days (24-hr day; 0.5E6 OH/cm3)

  HALF-LIFE= 12.541 Hrs

 

 

---------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) ----------

              ****** NO OZONE REACTION ESTIMATION ******

              (ONLY Olefins and Acetylenes are Estimated)

 

Experimental Database: NO Structure Matches

American settings

OH radical concentration: 1.5E+06 OH radicals/cm3Half-life: 12 h/day

---------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) ----------

 

Hydrogen Abstraction=  30.6584 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= 0.0461 E-12 cm3/molecule-sec

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

 

 OVERALL OH Rate Constant = 30.7044 E-12 cm3/molecule-sec = 2.65 E-06 cm3/molecule-day

  HALF-LIFE= 0.348 Days (12-hr day; 1.5E6 OH/cm3)

  HALF-LIFE= 4.180 Hrs

 

---------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) ----------

              ****** NO OZONE REACTION ESTIMATION ******

              (ONLY Olefins and Acetylenes are Estimated)

 

Experimental Database: NO Structure Matches

Conclusions:
In the atmosphere the substance is degraded by reaction with photochemically-produced hydroxyl radicals with a half-life between 4.2 and 12.5 hours, at different test conditions.
Executive summary:

Stability of the substance in the atmosphere was calculated using the software AOPWIN (v 1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals. The half-life for this reaction in air is estimated to be between 4.2 and 12.5 hours, at different test conditions.

Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
January 31, 2012
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:
See the attached justification.
Guideline:
other: ECHA Guidance on information requirements and chemical safety assessment - Chapter R.06: QSARs and grouping of chemicals
Principles of method if other than guideline:
See the justification for type of information.
Estimation method (if used):
PHOTOCHEMICAL REACTION WITH OH RADICALS

Standard European settings
- Concentration of OH radicals: 0.5E+06 OH/cm3
- Half life: 24 hr/day

Standard American settings
- Concentration of OH radicals: 1.5 E6 OH/cm3
- Half life: 12 hr/day

- Temperature for which rate constant was calculated: 25°C

- Software: AOPWIN v 1.92
Key result
DT50:
12.5 h
Test condition:
OH concentration: 0.5E+06 OH radicals/cm3; Half-life: 24 h/day (EU std conditions)
DT50:
4.2 h
Test condition:
OH concentration: 1.5E+06 OH radicals/cm3; Half-life: 12 h/day (USA std conditions)
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 d-1

Compound Being Estimated:

SMILES:O=C(OCCCCCCCC)c1cc(ccc1C(=O)OCCCCCCCC)C(=O)OCCCCCCCC

CHEM:trioctyl benzene-1,2,4-tricarboxylate

MOL FOR: C33 H54 O6

MOL WT: 546.79

European settings

OH radical concentration: 0.5E+06 OH radicals/cm3Half-life: 24 h/day

---------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) ----------

 

Hydrogen Abstraction= 30.6584 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= 0.0461 E-12 cm3/molecule-sec

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

 

 OVERALL OH Rate Constant = 30.7044 E-12 cm3/molecule-sec= 2.65 E-06 cm3/molecule-day

 

  HALF-LIFE= 0.523 Days (24-hr day; 0.5E6 OH/cm3)

  HALF-LIFE= 12.541 Hrs

 

 

---------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) ----------

              ****** NO OZONE REACTION ESTIMATION ******

              (ONLY Olefins and Acetylenes are Estimated)

 

Experimental Database: NO Structure Matches

American settings

OH radical concentration: 1.5E+06 OH radicals/cm3Half-life: 12 h/day

---------- SUMMARY (AOP v1.92): HYDROXYL RADICALS (25 deg C) ----------

 

Hydrogen Abstraction= 30.6584 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= 0.0461 E-12 cm3/molecule-sec

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

 

 OVERALL OH Rate Constant = 30.7044 E-12 cm3/molecule-sec= 2.65 E-06 cm3/molecule-day

  HALF-LIFE= 0.348 Days (12-hr day; 1.5E6 OH/cm3)

  HALF-LIFE=4.180 Hrs

 

---------- SUMMARY (AOP v1.91): OZONE REACTION (25 deg C) ----------

              ****** NO OZONE REACTION ESTIMATION ******

              (ONLY Olefins and Acetylenes are Estimated)

 

Experimental Database: NO Structure Matches

Validity criteria fulfilled:
yes
Conclusions:
The stability of the test material in the atmosphere was calculated using the software AOPWIN (v1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, with a half-life ranged from 4.2 to 12.5 hours, at different test conditions. The most conservative value was selected.
The overall degradation rate constant with OH radicals is estimated to be equal to 2.65E-6 cm3/(molecule-day).
Executive summary:

The stability of the test material in the atmosphere was calculated using the software AOPWIN (v1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, with a half-life ranged from 4.2 to 12.5 hours, at different test conditions. The most conservative value was selected.

The overall degradation rate constant with OH radicals is estimated to be equal to 2.65E-6 cm3/(molecule-day).

Description of key information

Half-life for reaction with photochemically-produced hydroxyl radicals estimated to be between 4.2 and 12.5 hours.
Overall OH Radicals Rate Constant = 2.65E-06 cm3/(molecule-day).

Key value for chemical safety assessment

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

Additional information

Stability of the substance in the atmosphere was calculated using the software AOPWIN (v 1.92). It is predicted that the substance will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals. The half-life for this reaction in air is estimated to be between 4.2 and 12.5 hours, at different test conditions.

The most conservative value (european settings) was selected.