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

Phototransformation in water

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Administrative data

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1994

Report date:

1994

Materials and methods

Study type:

direct photolysis

Test guideline

Qualifier:

according to guideline

Guideline:

EPA Guideline Subdivision N 161-2 (Photodegradation Studies in Water)

Deviations:

yes

Remarks:

This study was conducted in natural sunlight. Deficiencies concern the extrapolation of the photolysis kinetic results to 40-65 degrees North latitude.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Test material form:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Rohm and Haas, Batch No. 724.0209

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: 97.2 %
- Specific activity: 31.61 mCi/g
- Locations of the label: 14C label was in the 4 and 5 carbons

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Not described
- Stability under test conditions: The compound is hydrolytically stable at pH 7 (25°C; DT50 >60 days)
- Solubility and stability of the test substance in the solvent/vehicle: Water solubility is greater than 1000 ppm in distilled water
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: Dilution in sterile buffer
- Preliminary purification step (if any): No
- Final dilution of a dissolved solid, stock liquid or gel: 10 ppm 14C-CMIT

FORM AS APPLIED IN THE TEST (if different from that of starting material)
Liquid

Study design

Radiolabelling:

yes

Analytical method:

gas chromatography

high-performance liquid chromatography

mass spectrometry

other: liquid scintillation counter, thin layer chromatography

Details on sampling:

- Sampling intervals for the parent/transformation products: Days 0, 1, 4, 6, 8, and 15
- Sampling method: A sample was transferred from its photolysis tube into a sample vial, the photolysis tube rinsed with 1 mL of acetonitrile and the rinse added to the test solution.
- Sampling methods for the volatile compounds, if any: NaOH and ethylene glycol trap
- Sampling intervals/times for pH measurements: Prior to the study initiation and at sampling intervals (days 0, 1, 4, 6, 8, and 15)
- Sampling intervals/times for sterility check: Not described
- Sample storage conditions before analysis: All samples were radioassayed at the time of sampling and then stored at less than 0°C
- Other observation, if any (e.g.: precipitation, color change etc.): No

Buffers:

- pH: 7
- Type and final molarity of buffer: phosphate buffer 0.01 M
- Composition of buffer: 0.3471 g of Na2HPO4•7H2O and 0.1526 g of KH2PO4 with 250 mL of water

Light source:

sunlight

Details on light source:

- Location: Richmond, CA, USA
- Latitude: 37.45N
- Longitude: 122.26 W
- Hours of daylight: 11 to 11.5 h
- Time of year/month: From 20 February 1992 to 6 March 1992
- Light intensity: Average of 5.99 ± 1.81 W•min/cm2 (ranged from 1.50-7.98 W•min/cm2)

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test apparatus/vessels: quartz photolysis tubes which had an 11 mm inside diameter and were 205 mm in height
- Sterilisation method: Autoclave
- Measures to saturate with oxygen: Air pumped with a vacuum pump
- Details of traps for volatile, if any: 10 % NaOH and ethylene glycol traps
- Indication of test material adsorbing to the walls of test apparatus: No

TEST MEDIUM
- Volume used/treatment: 10 mL
- Kind and purity of water: Phosphate buffer
- Preparation of test medium: The phosphate buffer was prepared by adding 0.3471 g of Na2HPO4•7H2O and 0.1526 g of KH2PO4 with 250 mL of water to a 500 mL volumetric flask
- Renewal of test solution: No

REPLICATION
- No. of replicates (dark): 2
- No. of replicates (irradiated): 2

Duration of test at given test condition

Duration:

15 d

Temp.:

25 °C

Initial conc. measured:

10 mg/L

Reference substance:

no

Dark controls:

yes

Results and discussion

% Degradation

% Degradation 1

% Degr.:

79.6

Sampling time:

15 d

Test condition:

Natural sunlight

% Degradation 2

% Degr.:

62.4

Sampling time:

8 d

Test condition:

Natural sunlight

% Degradation 3

% Degr.:

49.5

Sampling time:

6 d

Test condition:

Natural sunlight

% Degradation 4

% Degr.:

32.8

Sampling time:

4 d

Test condition:

Natural sunlight

% Degradation 5

% Degr.:

12.2

Sampling time:

1 d

Test condition:

Natural sunlight

% Degradation 6

% Degr.:

8.5

Sampling time:

0 d

Test condition:

Natural sunlight

% Degradation 7

% Degr.:

< 5

Sampling time:

15 d

Test condition:

Dark

Dissipation half-life of parent compound

Key result

DT50:

6.6 d

Test condition:

Natural sunlight

Predicted environmental photolytic half-life:

Not calculated since natural sunlight was used as the light source

Transformation products:

yes

Identity of transformation products

Identity of transformation products 1

No.:

#1

Identity of transformation products 2

No.:

#2

Details on results:

HALF-LIFE
6.6 days

TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS (distinguish between dark and irradiated samples)
- Range of maximum concentrations in % of the applied amount at end of study period: 30.4% (Degradate #1) and 37.6% (Degradate #2)

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT (distinguish between dark and irradiated samples): Irradiated samples, 4.8 ± 3.1 %; Dark controls, 2.5 ± 3.1 %; and Total, 3.6 ± 3.3 %.

MINERALISATION (distinguish between dark and irradiated samples)
- % of applied radioactivity present as CO2 at end of study: 0.6% volatiles at the end of the 15 day sunlight exposure, negligible in dark conditions

VOLATILIZATION (distinguish between dark and irradiated samples)
- % of the applied radioactivity present as volatile organics at end of study: 0.6% volatiles at the end of the 15 day sunlight exposure, negligible in dark conditions

TRANSFORMATION PATHWAY
- Description of biotransformation pathway: The major degradative pathway involves cleavage of the isothiazolone ring
- Figure attached: No

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

This study fulfils the requirement for determining the effect of aqueous photolysis on the fate of CMIT in the environment. The half-life in natural sunlight is 6.6 days (rate constant, 0.105 day-1). The major photodegradation products are 5-chloro-3-methyl-4-thiazolin-3-one and N-methyl malonamic acid. The major degradative pathway involves cleavage of the isothiazolone ring.

Executive summary:

Sterile pH 7 phosphate buffer was prepared and dosed at nominal 10 ppm¹⁴C CMIT. Ten mL were aseptically transferred to quartz photolysis tubes and placed on a roof top in Richmond, CA, USA in a water bath maintained at 24.8 ± 0.5°C for 15 days. Air was passed through the tubes and evolved volatiles trapped using NaOH and ethylene glycol. Replicate tubes were removed at Days 0, 1, 4, 6, 8, and 15 and analyzed by radioassay and HPLC. Test guidelines wereU.S. Environmental Protection Agency, 40 CFR § 158, Environmental Fate Assessment Guidelines, Subdivision N, Chemistry, Environmental Fate 161-2. No actinometer study was performed since this was not a requirement of the guidelines at the time the study was performed.

This study fulfils the requirement for determining the effect of aqueous photolysis on the fate of CMIT in the environment. The half-life in natural sunlight is 6.6 days (rate constant, 0.105 day-1). The major photodegradation products are 5-chloro-3-methyl-4-thiazolin-3-one and N-methyl malonamic acid. The major degradative pathway involves cleavage of the isothiazolone ring.