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Environmental fate & pathways

Phototransformation in water

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Reference
Endpoint:
phototransformation in water
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Study type:
direct photolysis
Qualifier:
no guideline followed
Principles of method if other than guideline:
The 14C-test substance at 1 ppm in circulated river water was exposed to sunlight and ambient temperatures for 8 weeks. Two 50 µL aliquots were counted in Fluoralloy DXA® to determine total radioactivity.
GLP compliance:
no
Specific details on test material used for the study:
- Substance name: 14C-Methomyl
- Purity: Not reported
Radiolabelling:
yes
Analytical method:
other: thin layer chromatography
Light source:
sunlight
Duration:
8 wk
Initial conc. measured:
1 other: ppm
Reference substance:
yes
Dark controls:
no
Key result
DT50:
> 1 wk
Test condition:
Ambient temperature
Transformation products:
yes
Remarks:
S-methyl N-hydroxythioacetimidate (12%); CO2 (65%)
Conclusions:
The 14C-test substance at 1 ppm in circulated river water was exposed to sunlight and ambient temperatures for 8 weeks. The test substance degraded rapidly with a half-life of slightly more than 1 week.
Executive summary:

The 14C-test substance at 1 ppm in circulated river water was exposed to sunlight and ambient temperatures for 8 weeks. The test substance degraded rapidly with a half-life of slightly more than 1 week. The first degradation product was S-methyl N-hydroxythioacetimidate, followed by extensive breakdown to 14CO2 which accounted for 65% of the original test substance after 8 weeks. After 2 weeks, the S-oxide of S-hydroxythioacetimidate was also detected and small amounts were still present at the conclusion of the experiment. In addition, traces of a polar fraction appeared which has not been further characterized. At the conclusion of the experiment, 9% of the original treatment was recovered by combustion of the sediment and biological film found on the walls of the container.

Description of key information

Study Type

 Study Details Value  Guideline Reliability 
 Phototransformation in water

Exposure to artifical sunlight at 10 and 100 ppm

DT50 = 5.5 days at 10 ppm

DT50 = 2 days at pH = 100 ppm

EPA 63-13

Key value for chemical safety assessment

Half-life in water:
2 d

Additional information