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Diss Factsheets

Environmental fate & pathways

Phototransformation in air

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Link to relevant study record(s)

Reference
Endpoint:
phototransformation in air
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The US EPA EPISUITE modelling programme is adequately validated and therefore suitable for use.
Qualifier:
no guideline required
Principles of method if other than guideline:
QSAR calculation addressing degradation through the 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.
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
not applicable
Estimation method (if used):
AOPWIN v1.92
Key result
DT50:
>= 4.162 - <= 13.097 h
Test condition:
Qsar calculation
Transformation products:
no

OVERALL OH Rate Constant = 30.8405 E-12 cm3/molecule-sec  

HALF-LIFE =    0.347 Days (12-hr day; 1.5E6 OH/cm3)   

HALF-LIFE =    4.162 Hrs

OVERALL OZONE Rate Constant =    2.100000 E-17 cm3/molecule-sec   

HALF-LIFE =     0.546 Days (at 7E11 mol/cm3)   

HALF-LIFE =    13.097 Hrs

Validity criteria fulfilled:
not applicable
Conclusions:
The primary route of removal from the atmosphere is through the gas-phase reaction between ozone or photochemically produced hydroxyl radicals and the test substance. The model shows that removal from the atmosphere is rapid, therefore the material is not expected to accumulate in this compartment.
Executive summary:

The AOPWIN v1.92 model indicates that the test substance is rapidly removed from the atmosphere by both the gas-phase reaction with photochemically produced hydroxyl radicals and with ozone. The DT50 via the OH route is 4.162 h and via the ozone route 13.097 h.

Description of key information

Phototransformation in air was estimated using the AOPWIN v1.92 model, which indicated that the substance is rapidly removed from the atmosphere by both the gas-phase reaction with photochemically produced hydroxyl radicals and with ozone. The DT50 via the OH route was 4.162 h and via the ozone route 13.097 h. The mean half-life was 8.629 h.

Key value for chemical safety assessment

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

Additional information