reaction mass of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-2H -isothiazol-3-one

Phototransformation in air

Administrative data

Endpoint:

phototransformation in air

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Technical Guidance Document, Chapter 3, Section 7.3.1

Deviations:

not applicable

GLP compliance:

no

Remarks:

Not applicable

Test material

Test material information

Constituent 1

Test material form:

not specified

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Stability under test conditions: Aqueous Photolytic half-life is 11.1 days
- Solubility and stability of the test substance in the solvent/vehicle: Solubility in water is >16.3 g/L

Study design

Estimation method (if used):

PHOTOCHEMICAL REACTION WITH OH RADICALS
- Concentration of OH radicals: 6.5 x 10e5 molecules/cm3

Reference substance:

no

Results and discussion

Dissipation half-life of parent compound

Dissipation half-life of parent compound 1

Key result

DT50:

12.7 h

Test condition:

Half-life due to hydroxyl radical

Dissipation half-life of parent compound 2

Key result

DT50:

29.9 h

Test condition:

Half-life due to nitrate radical

Degradation rate constant

Degradation rate constant 1

Key result

Reaction with:

OH radicals

Rate constant:

0 cm³ molecule-1 d-1

Degradation rate constant 2

Key result

Reaction with:

other: NO3 radicals

Rate constant:

0 cm³ molecule-1 d-1

Transformation products:

not measured

Remarks:

Potential phototransformation products are hypothesized based on previously conducted environmental fate studies, i.e. aqueous photolysis, hydrolysis, and water/soil metabolism

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Daylight photolysis is the dominant phototransformation procedure for MIT and its potential metabolites. MIT photodegrades quickly with half-life of 12.7 hours and the half-lives of its metabolites range from 18.6-24.1 hours, based on a 24h day and a concentration of OH-radicals in atmosphere of 6.5 x 10e5 molecules/cm3. Based on a 24h day and a concentration of OH-radicals in atmosphere of 5 x 10e5 molecules/cm3 according to the TGD, the half life is 16.6 h. The effect from CMIT and its potential photodegradation products towards global warming is minimal. Therefore, CMIT and its photodegradation metabolites impose no effect to global warming.

Executive summary:

The guideline followed is that described in the Technical Guidance Document, Chapter 3, Section 7.3.1. The phototransformation rate constant of CMIT is calculated using SAR method. Global average OH and NO3 radical concentrations in daylight and night hours are used. Potential phototransformation products of CMIT are hypothesized based on information from previous studies. The estimation is demonstrated to be accurate by comparing the rate constant of CMIT with that of six compounds which have similar bond types.

Due to relative low vapor pressure and high water solubility, the concentration of CMIT in the troposphere is expected to be low. This ensures that the photodegradation of the radicals with CMIT follows a pseudo first-order kinetics required by SAR calculation method. Due to the presence of nitrogen and sulfur bonds, CMIT has a large phototransformation rate constant. The parent compound quickly photodegrades during the daylight with half-life of 12.7 hours. Due to the presence of nitrogen and sulfur bonds, all potential photodegradation products are expected to be very reactive to photodegradation with half-lives ranging from 18.6 -24.1 hours.

Daylight photolysis is the dominant phototransformation procedure for CMIT and its potential metabolites. CMIT photodegrades quickly with half-life of 12.7 hours and the half-lives of its metabolites range from 18.6-24.4 hours , based on a 24h day and a concentration of OH-radicals in atmosphere of 6.5 x 10e5 molecules/cm3. Based on a 24h day and a concentration of OH-radicals in atmosphere of 5 x 10e5 molecules/cm3 according to the TGD, the half life is 16.6 h. The effect from CMIT and its potential photodegradation products towards global warming is minimal. Therefore, CMIT and its photodegradation metabolites impose no effect to global warming.