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Environmental fate & pathways

Phototransformation in air

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Reference
Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Study period:
2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Qualifier:
no guideline followed
Principles of method if other than guideline:
Calculation using AOPWIN v.1.92 included in EPISuite v 4.11, 2000 - 2012
EPI Suite was developed by the EPA's Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC), Coyright 2000-2012 U.S. Environmental Protection Agency
GLP compliance:
no
Estimation method (if used):
Calculated using AOPWIN v.1.92 included in EPISuite v 4.11, 2000 - 2012
Light source:
other: Not applicable - Calculation method
Details on light source:
Not applicable - Calculation method
Details on test conditions:
Sensitiser (for indirect photolysis): OH
Sensitiser concentration: 500,000 molecule/cm³, 24 h/d
Reference substance:
no
% Degr.:
50
Sampling time:
35.5 h

1) Defined Endpoint: Rate constant for the atmospheric, gas-phase reaction between photochemically produced hydroxyl radicals and organic chemicals at 25°C.

2) Unambiguous algorithm: The molecule is separated into distinct fragments. The reaction rate constant for hydroxyl radicals are the summation of the following mechanisms:

Hydrogen Abstraction = 0.0000 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 =10.8423 E-12 cm3/molecule-sec

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

** Designates Estimation(s) Using ASSUMED Value(s)

As depending on the structure of the substance, OH-radicals generally react by one or more of the above mentioned pathways, the result of 0.0000 E-12 cm3/molecule-sec for each mechanism indicate that these mechanisms are not relevant for the substance of interest. An "assumed value" is applied, showing that a structure fragment that has not been assigned a numeric value by the developer of the estimation methods used by AOPWIN or derived explicitly from experimental values.

OH Addition to Aromatic Rings Calculation:

Most negative Es+ = -0 .200

Log Kar = -11.71 - 1.34(Es+) cm3/molecule-sec

Ring #1 Kar = 3.6141 E-12 cm3/molecule-sec

Ring #2 Kar = 3.6141 E-12 cm3/molecule-sec

Ring #3 Kar = 3.6141 E-12 cm3/molecule-sec

TOTAL Kar = 10.8423 E-12 cm3/molecule-sec

Note: The bimolecular rate constant karom is expressed as Kar by the program

Validity criteria fulfilled:
yes
Remarks:
accepted calculation method
Conclusions:
Based on the assumption of a 24h-day and a concentration of 0.5x10E6 OH/cm3 the calculated half-life of TPP is 35.5 hours
Executive summary:

Using the AOP Program v.1.92 implemented in EPI Suite the half-life of TPP was estimated to be 35.5 h related to the atmospheric oxidation (based on the assumption of a 24h-day and a concentration of 5x10E5 OH/cm3).

Description of key information

A calculation based on a 24 hour-day and a concentration of 5x10E5 OH/cm3 gave a half-life of TPP of 35.5 hours

Key value for chemical safety assessment

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

Additional information