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Environmental fate & pathways

Phototransformation in air

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Reference
Endpoint:
phototransformation in air
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method.
Principles of method if other than guideline:
Method: other (calculated): Tropospheric lifetime of DMF was calculated according to the method of Atkinson (1988).
GLP compliance:
no
Estimation method (if used):
Method of achieving rate constant by regarding each functional groups of molecules, according to Atkinson (see: Atkinson, R. (1988): Estimation of gas-phase hydroxyl radical rate constants for organic chemicals. Environ. Tox. Chem. 7, 435-442)
Light source:
other: calculation
Details on test conditions:
Sensitiser (for indirect photolysis): OH
Sensitiser concentration: 500000 molecule/cm³
% Degr.:
50
Sampling time:
2 h
Test condition:
24h day
Reaction with:
OH radicals
Rate constant:
0 cm³ molecule-1 s-1
Transformation products:
not measured

Rate constant (for indirect photolysis): = 0.00000000021 cm³/(molecule*sec)
Degradation in % (for indirect photolysis): = 50 after 2 hour(s)

Validity criteria fulfilled:
yes
Conclusions:
DT50 = 2h
Executive summary:

Tropospheric lifetime of DMF was calculated according to the method of Atkinson (1988). For calculation of half-life, a 24 hour day was assumed. Sensitiser (for indirect photolysis): OH Sensitiser concentration: 500000 molecule/cm³

Results: DT50 = 2h. Rate constant (for indirect photolysis): = 0.00000000021 cm³/(molecule*sec)

Description of key information

Phototransformation in air; tropospheric lifetime of DMF was calculated according to the method of Atkinson (1988); non-GLP. For calculation of half-life, a 24 hour day was assumed. Results: DT50 = 2h.

Rate constant (for indirect photolysis): = 0.00000000021 cm³/(molecule*sec)

Key value for chemical safety assessment

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

Additional information

Based on the key study, the test substance is expected to rapidly photodegrade in air under the influence of OH- radicals. The rate constant was calculated to be 0.00000000021 cm³/(molecule*sec), resulting in a half-life of 2 hours. The calculation parameters were 500000 OH-radicals/cm³ and a 24 -hour day.

Further study (Chemservice, 2020): 24 h day - Rate constant (for indirect photolysis): = 0.0000000000175926 cm³/(molecule*sec) Degradation in % (for indirect photolysis): = 50 after 22 hour(s); 12 h day - Rate constant (for indirect photolysis): = 0.0000000000175926 cm³/(molecule*sec) Degradation in % (for indirect photolysis): = 50 after 7.3 hour(s)

The calculation indicates a rapid degradation of DMF when potentially entering the atmosphere. It is not to be expected that DMF will accumulate in the air or be transported in the gaseous phase over long distances. Hence, air will not be an environmental compartment of concern for the compound.