2-tetradecyloxirane, reaction products with boric acid

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 May 2020 to 25 May 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)

Version / remarks:

April 2002 (aerobic part)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: SANTE/2020/12830 Guidance Document on Pesticide Analytical Methods for Risk Assessment and Post-approval Control and Monitoring Purposes.

Version / remarks:

Rev.1; February 2021:

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

natural sediment: freshwater

Details on source and properties of sediment:

See below.

Duration of test (contact time):

ca. 50 h

Initial conc.:

0.325 other: μg/mL

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

STUDY DESIGN
- Test item was applied to the water layer of samples of two aquatic sediment types at a nominal rate of 0.325 μg/mL.
- The volume ratio of wet sediment to water in each sample was between 1:3 and 1:4.
- Aquatic sediment systems were acclimatised under aerobic conditions prior to test item application until reasonable stability had been established with respect to the pH, oxygen concentration and redox potential in the water and the pH and redox potential in the sediment.
- Samples were arranged in flow-through systems. The systems were incubated in darkness at 12 ± 2 °C for periods of up to 20 days prior to analysis.
- At appropriate time intervals, samples were taken for analysis. An aliquot of water was removed and after the addition of a saturated solution of borax was partitioned into ethyl acetate. The entire sediment sample was extracted with ethyl acetate prior to an ENVI Carb clean up. Quantitation was performed using liquid chromatography with tandem mass spectrometric detection (LC-MS/MS).
- Additional samples were established for the determination of the microbiological activity at the start and end of the incubation period and the measurement of the pH and redox potential in both phases and oxygen content in the water phase.

Reference substance:

not required

Compartment:

natural water: freshwater

DT50:

13.3 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Calwich Abbey Lake.

Compartment:

natural water: freshwater

DT50:

15 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Lumsdale Middle Pond

Compartment:

natural sediment: freshwater

DT50:

10.8 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Calwich Abbey Lake

Compartment:

natural sediment: freshwater

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Lumsdale Middle Pond

Remarks:

< 0.06 μg/mL (LOQ)

Compartment:

entire system

DT50:

14.5 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Calwich Abbey Lake

Compartment:

entire system

DT50:

15 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: Lumsdale Middle Pond

Transformation products:

yes

No.:

#1

No.:

#2

Details on transformation products:

Refer to the document 'Expert opinion on degradation pathways of EC 701-392-2' attached to this robust study summary.

Details on results:

CHARACTERISATION OF THE TEST SYSTEM
- The sampling details for each aquatic sediment were shown in Appendix 3 of the full study report. This table also contained the results of various measurements (pH and oxygen saturation) made at the sampling sites.
- Details of the sediment and water analyses subsequently carried out on sieved portions of each sediment and water were given in Appendix 4 of the full study report.
- Appendix 5 contained the results of the microbiological analyses of sediment and water, at the start and end of the incubation period in the main experiment. Both aquatic sediments were microbiologically active throughout the incubation period and there were no appreciable differences in levels of the various organisms at the end of the incubation period between untreated samples and samples treated with solvent.

INCUBATION CONDITIONS
- Results of measurements of water and sediment redox potential, water and sediment pH and water oxygen content were shown in Appendix 6 of the full study report.
- For Calwich Abbey Lake aquatic sediment, oxygen levels in the water (in the range 82.9 to 121.8 % saturation) and corrected redox potentials in the water (greater than +200 mV) and sediment (less than -200 mV) were indicative of an aerobic, oxidising water phase and a reducing sediment phase.
- For Lumsdale Middle Pond aquatic sediment, oxygen levels in the water (in the range 82.5 to 93.5 % saturation) and corrected redox potentials in the water (greater than +200 mV) and one of the sediments (less than -200 mV) were indicative of an aerobic, oxidising water phase and a reducing sediment phase.
- The temperature of the room generally remained within the range 12 ± 2 °C throughout the incubation period except on one occasion where a maximum temperature of 15.1 °C was recorded. The temperature deviation from this range occurred for approximately 1 hour. This was considered not to have affected the outcome or integrity of the study.

PRELIMINARY EXPERIMENT
- Test item was applied at a rate of 0.325 μg/mL to Calwich Abbey Lake aquatic sediment samples.
- Single sediment/water samples from Calwich Abbey Lake were taken for analysis immediately after test substance application and at 6 and 30 hours after treatment in order to determine appropriate sampling occasions for the main experiment. The results indicated that test item had degraded to approximately 68 % of T0 after 30 hours in the Calwich Abbey aquatic sediment samples.
- Based on the preliminary results a main experiment was conducted for both Calwich Abbey Lake and Lumsdale Middle Pond aquatic sediment systems. Duplicate vessels were analysed at zero-time and after 24 hours and 48 hours of incubation. The results indicated that test item had degraded to approximately < 5% of T0 after 48 hours in
both aquatic sediment samples. Based on these results proposed sampling intervals were determined.

MAIN EXPERIMENT
- Test item was applied at a rate of 0.325 μg/mL to Calwich Abbey Lake and Lumsdale Middle Pond aquatic sediment samples.
- Duplicate sediment/water samples from each aquatic sediment were taken for analysis immediately after test substance application and after test item application and at 4, 8, 12, 26, 38 and 50 hours after treatment. The concentrations of test item in sediment, water and sediment and water were summarised in Tables 5 to 10 of the full study report. Example chromatograms of rate of degradation sediment/water sample extracts are presented in Figures 11 to 13, 16 to 18, 21 to 23 and 26 to 28 of the full study report.
- In Calwich Abbey Lake aquatic sediment, the concentration in the water layer declined from a mean of 0.342 μg/mL at time zero to < LOQ after 38 hours of incubation. In sediment, the concentration increased to a mean of 0.447 μg/g after 12 hours and then decreased to < LOQ after 38 hours of incubation.
- In Lumsdale Middle Pond aquatic sediment, the concentration in the water layer declined from a mean of 0.319 μg/mL at time zero to 0.0152 μg/mL after 50 hours of incubation. In sediment, the concentration remained at < LOQ.
- There were forty-five batches in total performed during the study and twenty-two were reported. The batches that were not reported did not meet the acceptance criteria.

PROCEDURAL RECOVERIES
- Rate of degradation samples were analysed in suitably sized batches together with an untreated sample (control) and an untreated sample fortified with the test item, which acted as a procedural recovery sample to ensure the validity of the method on the day of analysis. Batch analysis performed and the associated procedural recovery results were presented in Tables 11 to 14 of the full study report.
- The mean procedural recovery results obtained for each batch of sample analysis were within the acceptable range of 70 to 120 %, demonstrating the methodology to be working within its requirements. Example chromatograms of control (untreated) samples and procedural recovery samples werepresented in Figures 9, 10, 14, 15, 19, 20, 24 and 25 of the full study report.

KINETIC ANALYSIS
- DT50 and DT90 values for the decline of test item from the water, the sediment and from the total aquatic sediment system were calculated on the results obtained using Single First Order (SFO) kinetic models as described in Appendix 7 of the full study report and summarised below and in Table 16 (below).

VALIDATION OF ANALYTICAL METHODOLOGY
- Calibration (linearity): The response of the LC-MS/MS system to the test item was shown to give a quadratic response over the range of concentrations 0.01 μg/mL to 1 μg/mL. Typical calibration data were presented in Figures 1 and 2 of the full study report. Typical chromatograms of the calibration standards were presented in Figures 3 to 8 of the full study report.
- Limit of detection (LOD): The LOD of the method is defined as the value of the lowest calibration standard giving rise to a measurable chromatographic response. The LOD of the analytical system was confirmed as 0.01 μg/mL (equivalent to 0.02 μg/g in sediment and 0.005μg/mL in water).
- Accuracy and precision: The analytical method was validated at 0.06 and 1.3 μg/g in sediment. The mean recoveries for the analytical method validation were within the acceptable range of 70 to 120 %, demonstrating accuracy (recovery) of the method. The relative standard deviation (RSD) obtained at each fortification level was within the acceptable range of ≤ 20%, demonstrating precision of the method. The validation data were presented in Tables 1 and 3 of the full study report and the accuracy and precision data obtained are summarised in the table below.
- The analytical method was validated at 0.015 and 0.325 μg/mL in water. The mean recoveries for the analytical method validation were within the acceptable range of 70 to 120 %, demonstrating accuracy (recovery) of the method. The relative standard deviation (RSD) obtained at each fortification level was within the acceptable range of ≤ 20 %, demonstrating precision of the method. The validation data were presented in Tables 2 and 4 of the full study report and the accuracy and precision data obtained are summarised in the table below.

LIMIT OF QUANTIFICATION (LOQ)
- The LOQ of the method is defined as the lowest fortification level at which acceptable recovery data are obtained.
- The validation of the methodology for the determination of test item demonstrated that it can be accurately determined at a LOQ of 0.06 μg/g in sediment and 0.015 μg/mL in water.

SPECIFICITY
- No significant interferences (greater than the equivalent of 30% of the LOQ) were found when the method was applied to control samples, thus assuring the specificity of the method.

SAMPLE FINAL EXTRACT STABILITY
- The sample final extract stability samples indicated that the test item was stable in the final extracts of the two water and two sediment types for a period of at least 5 days when stored at approximately –20 °C.
- The results of the sample final extract stability tests were presented in Table 15 of the full study report.

TABLE 16 – KINETIC DATA FOR TEST ITEM IN AQUATIC SEDIMENT SYSTEMS

Aquatic sediment	Compartment	Kinetic model	DT50 (hours)	DT90 (hours)
Calwich Abbey Lake	Water	SFO	13.3	44.3
Lumsdale Middle Pond	Water	SFO	15	49.9
Calwich Abbey Lake	Sediment	SFO	10.8	35.9
Lumsdale Middle Pond	Sediment	SFO	No decline (< LOQ)	No decline (< LOQ)
Calwich Abbey Lake	Total system	SFO	14.5	48.3
Lumsdale Middle Pond	Total system	SFO	15	49.9

 

ACCURACY AND PRECISION DATA SUMMARY FOR SEDIMENT

Sediment	Fortification level (μg/g)	Number of replicates	Recovery range (%)	Mean recovery (%)	Relative standard deviation
Calwich Abbey Lake	0.06	5	78 to 94	83	7.6
Calwich Abbey Lake	1.3	5	85 to 95	88	4.4
Lumsdale Middle Pond	0.06	5	79 to 100	90	10.9
Lumsdale Middle Pond	1.3	5	88 to 102	93	5.7

 

ACCURACY AND PRECISION DATA SUMMARY FOR WATER

Sediment	Fortification level (μg/g)	Number of replicates	Recovery range (%)	Mean recovery (%)	Relative standard deviation
Calwich Abbey Lake	0.015	5	81 to 87	85	2.6
Calwich Abbey Lake	0.325	5	89 to 95	91	2.6
Lumsdale Middle Pond	0.015	5	85 to 88	87	1.3
Lumsdale Middle Pond	0.325	5	93 to 94	94	0.5

Conclusions:

The test item degraded rapidly in both aquatic sediment systems. The estimated DT50 values in sediment were determined to be 10.8 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond). The estimated DT90 values in sediment were 35.9 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond).

Executive summary:

GUIDELINE

The study was performed in compliance with OECD Guideline for the Testing of Chemicals No. 308: Aerobic and

Anaerobic Transformation in Aquatic Sediment Systems (April 2002) (aerobic part) and SANTE/2020/12830, Rev.1 of 24 February 2021: Guidance Document on Pesticide Analytical Methods for Risk Assessment and Post-approval Control and Monitoring Purposes.

 

METHODS

The rate of degradation (DT50, DT90) of test item was studied in two aquatic sediment systems incubated under aerobic conditions in the laboratory. The sediment from Calwich Abbey Lake was a silt loam with a higher organic carbon content while that from Lumsdale Middle Pond was a sand with a lower organic carbon content. Samples of each aquatic sediment system were allowed to acclimatise before being treated with test item at a nominal rate of 0.325 μg/mL based on the amount of water in the test vessel including that present within the sediment. The samples were incubated under aerobic conditions at about 12 °C in darkness for periods of up to 50 hours. At each sampling occasion, the amounts of test item in the sediment/water samples were determined using validated analytical methodologies. Duplicate samples from each aquatic sediment system were taken for analysis immediately after test item application and at intervals of up to 50 hours.

 

RESULTS

In Calwich Abbey Lake aquatic sediment, the concentration in the water layer declined from a mean of 0.342 μg/mL at time zero to < LOQ after 38 hours of incubation. In sediment, the concentration increased to a mean of 0.447 μg/g after 12 hours and then decreased to < LOQ after 38 hours of incubation.

 

In Lumsdale Middle Pond aquatic sediment, the concentration in the water layer declined from a mean of 0.319 μg/mL at time zero to 0.0152 μg/mL after 50 hours of incubation. In sediment, the concentration remained at < LOQ, therefore no decline was observed.

 

DT50 and DT90 values for the decline of test item from the water, the sediment and from the total aquatic sediment system were calculated on the results obtained using Single First Order (SFO) kinetic models are shown below.

Assessment	Calwich Abbey Lake DT50 (hours)	Calwich Abbey Lake DT90 (hours)	Lumsdale Middle Pond DT50 (hours)	Lumsdale Middle Pond DT90 (hours)
Water	13.3	44.3	15	49.9
Sediment	10.8	35.9	No decline (< LOQ)	ND
Total system	14.5	48.3	15	49.9

 

CONCLUSION

The test item degraded rapidly in both aquatic sediment systems. The estimated DT50 values in sediment were determined to be 10.8 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond). The estimated DT90 values in sediment were 35.9 hours (Calwich Abbey Lake) and < LOQ (Lumsdale Middle Pond).

Reference 2

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 May 2020 to 01 December 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)

Version / remarks:

April 2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Commission Regulation (EU) No 283/2013 in accordance with Regulation (EC) No 1107/2009.

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: SANCO/3029/99

Version / remarks:

Rev 4

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on source and properties of surface water:

- Origin: River Dove, Eye, Suffolk, UK
- Geographic coordinates (longitude/latitude): 52.319907/1.155036
- Date of sampling: 16 November 2020
- Water body type: River
- Appearance: Pale brown, moderately turbid
- Sampling depth: 25 cm
- Temperature just below water surface: 9.47 °C
- pH: 7.735
- Oxygen saturation just below water surface: 77.8 %

Duration of test (contact time):

ca. 24 h

Initial conc.:

0.325 other: μg/mL

Based on:

test mat.

Initial conc.:

0.065 other: μg/mL

Based on:

test mat.

Parameter followed for biodegradation estimation:

test mat. analysis

Details on study design:

STUDY DESIGN
- Test item was applied to surface water at two nominal concentrations of 0.325 μg/L and 0.065 μg/L in duplicate. The test vessels were incubated with continuous stirring in the dark at 12 ± 2 °C and samples of treated surface water were taken for analysis at appropriate time intervals.
- Additional samples were established for the determination of the microbiological activity at the start and end of the incubation period and the measurement of the pH and oxygen content of the surface water.

Reference substance:

not required

Compartment:

natural water: freshwater

DT50:

4.9 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: concentration 0.325 μg/mL

Compartment:

natural water: freshwater

DT50:

3.4 h

Type:

other: single first order (SFO) model

Temp.:

12 °C

Remarks on result:

other: concentration 0.065 μg/mL

Transformation products:

yes

No.:

#1

No.:

#2

Details on transformation products:

Refer to the document 'Expert opinion on degradation pathways of EC 701-392-2' attached to this robust study summary.

Details on results:

DEGRADATION OF TEST ITEM
- For the preliminary experiment, a single aliquot of surface water was taken from the test vessel for analysis immediately after test substance application and at 6 and 12 hours after treatment in order to determine appropriate sampling occasions for the main experiment. The results indicated that there was significant degradation of test item in surface water after 12 hours. Consequently, sampling occasions for the main experiment were selected to span 24 hours.
- The concentrations of test item in surface water were summarised in Tables 2 and 3 of the full study report.
- Example chromatograms of rate of degradation surface water sample extracts were presented in Figures 8, 9, 10 and 11 of the full study report. The decline information is summarised below:
- Concentration 0.325 μg/mL: the mean test item detected declined from 0.300 μg/mL at zero-time to 0.0215 μg/mL at 24 hours.
- Concentration 0.065 μg/mL: the mean test item detected declined from 0.0538 μg/mL at zero-time to < LOQ at 24 hours.
- DT50 and DT90 values for the decline of the test item in the surface water were calculated as described in Appendix 5 of the full study report.
 
PROCEDURAL RECOVERIES
- Rate of degradation samples were analysed in suitably sized batches together with untreated samples (controls) and untreated samples fortified with the test item, which acted as procedural recovery samples to ensure the validity of the method on each occasion of analysis. Batch analysis performed and the associated procedural recovery results were presented in Table 4 of the full study report.
- The procedural recovery results obtained for each batch of sample analysis were within the acceptable range of 70 to 110 %, demonstrating the methodology to be working within its requirements.
- Example chromatograms of control (untreated) samples and procedural recovery samples were presented in Figures 5, 6 and 7 of the full study report.
 
CHARACTERISATION OF THE TEST SYSTEM
- The sampling details for the surface water were shown in Table 8 of the full study report. Additionally, this table contains the results of various measurements (pH, oxygen saturation) made at the sampling site. Table 9 of the full study report contained details of the water analyses subsequently carried out on filtered portions of surface water.
- Results of the microbiological analyses of surface water were given in Table 10 of the full study report, at the start and end of the incubation period in the main experiment. The surface water was microbiologically active throughout the incubation period and there were no appreciable differences in levels of the various organisms at the end of the incubation period between untreated samples and samples treated with solvent.
 
INCUBATION CONDITIONS
- Results of measurements of the pH and oxygen content of the surface water were shown in Appendix 4 of the full study report.
- During the incubation period, oxygen levels in the water (in the range 98.3 to 104.3 % saturation) were indicative of an aerobic surface water.
- The temperature of the room remained within the range 12 ± 2 °C throughout the incubation period.
 
KINETIC ANALYSIS
- DT50 and DT90 values for the decline of test item in the surface water for each concentration were shown in Table 11 of the full study report.
- The estimated DT50 values calculated using Single First Order (SFO) kinetic models for the decline of test item in the surface water were 4.9 hours and 3.4 hours at 0.325 μg/mL and 0.065 μg/mL concentrations, respectively.
- The estimated DT90 values calculated using Single First Order (SFO) kinetic models for the decline of test item in the surface water were 16.4 hours and 11.3 hours at 0.325 μg/mL and 0.065 μg/mL concentrations, respectively.
- More details of the kinetic analysis, including the modelled lines of best fit were shown in Appendix 5 of the full study report.
 
VALIDATION OF ANALYTICAL METHODOLOGY
- Calibration (linearity): The response of the LC-MS/MS system to test item was shown to give a quadratic response over the range of concentrations 0.025 to 2.5 μg/mL. Typical calibration data was presented in Figure 1 of the full study report. Typical chromatograms of the calibration standards were presented in Figures 2, 3 and 4 of the full study report.
- Limit of Detection (LOD): The LOD of the method is defined as the value of the lowest calibration standard giving rise to a measurable chromatographic response. The LOD of the analytical system was confirmed as 0.025 μg/mL, equivalent to 0.001 μg/mL in surface water.
- Accuracy and precision: The analytical method was validated at 0.00325 μg/mL and 0.325 μg/mL in surface water. The mean recoveries for the analytical method validation were within the acceptable range of 70 to 110 %, demonstrating accuracy (recovery) of the method. The relative standard deviation (RSD) obtained at each fortification level was within the acceptable range of≤20 %, demonstrating precision of the method. The validation data was presented in Table 1 of the full study report the accuracy and precision data are summarised in the table below.
- Limit of Quantification (LOQ): The LOQ of the method is defined as the lowest fortification level at which acceptable recovery data are obtained. The validation of the methodology for the determination of test item demonstrated that it can be accurately determined at a LOQ of 0.00325 μg/mL in surface water.
- Specificity: No significant interferences (greater than the equivalent of 30 % of the LOQ) were found when the method was applied to control samples, thus assuring the specificity of the method.
- Sample final extract stability: The sample final extract stability samples indicated that test item was stable in the final extracts of surface water for a period of at least 7 days when stored at approximately–20 °C. The results of the sample extract stability test were presented in Table 5 of the full study report.
- Analytical standard solutions storage stability: The analytical standard solutions storage stability test indicated that a 1 mg/mL stock solution was stable in tetrahydrofuran:methanol for a period of at least 11 days when stored at approximately +4°C in the dark. The analytical standard solutions storage stability test indicated that a 10 μg/mL intermediate calibration solution was stable in methanol:tetrahydrofuran:1% borax in water (25:25:50 v:v:v) for a period of at least 10 days when stored at approximately +4 °C in the dark. The stability data were summarised in Tables 6 and 7 of the full study report.

ACCURACY AND PRECISION DATA SUMMARY

Fortification level (μg/mL)	Number of replicates	Recovery range (%)	Mean recovery (%)	Relative standard deviation (%)
0.00325	5	104 to 110	106	2.1
0.325	5	91 to 94	93	1.5

Conclusions:

The test item degraded rapidly in surface water with an estimated DT50 value of 4.9 hours (at 0.325 μg/mL) and 3.4 hours (at 0.065 μg/mL) and an estimated DT90 value of 16.4 hours (at 0.325 μg/mL) and 11.3 hours (at 0.065 μg/mL).

Executive summary:

GUIDELINE

The study was performed in compliance with OECD Guideline for the Testing of Chemicals 309: Aerobic Mineralisation in Surface Water–Simulation Biodegradation Test (April 2004), Commission Regulation (EU) No 283/2013 in accordance with Regulation (EC) No 1107/2009 and SANCO/3029/99 (Rev.4).

 

METHODS

The rate of degradation (DT50, DT90) of test item was studied in surface water under aerobic conditions in the laboratory. Surface water vessels were set up and allowed to acclimatise at 12 ± 2 °C in the dark overnight before being treated with test item (in duplicate at each concentration) at nominal application rates of 0.325 μg/mL and 0.065 μg/mL. The surface water samples were incubated with continuous stirring to maintain aerobic conditions at 12 ± 2 °C in darkness for periods of up to 24 hours. At each sampling occasion, the amounts of test item in the surface water vessels were determined using validated analytical methodology. Aliquots of surface water samples were taken for analysis immediately after test item application and at intervals up to 24 hours.

 

RESULTS

The concentration of test item declined at both concentrations and is summarised below:

(a) Concentration 0.325 μg/mL: the mean test item detected declined from 0.300 μg/mL at zero-time to 0.0215 μg/mL at 24 hours.

(b) Concentration 0.065 μg/mL: the mean test item detected declined from 0.0538 μg/mL at zero-time to < LOQ at 24 hours.

 

DT50 and DT90 values for the decline of the test item in surface water were calculated using Single First Order (SFO) kinetic models and values are shown in the table below:

Concentration	Kinetic Model	DT50 (hours)	DT90 (hours)
0.325 μg/mL	SFO	4.9	16.4
0.0605 μg/mL	SFO	3.4	11.3

 

CONCLUSION

The test item degraded rapidly in surface water with an estimated DT50 value of 4.9 hours (at 0.325 μg/mL) and 3.4 hours (at 0.065 μg/mL) and an estimated DT90 value of 16.4 hours (at 0.325 μg/mL) and 11.3 hours (at 0.065 μg/mL).

Key value for chemical safety assessment

Half-life in freshwater:

4.9 h

at the temperature of:

12 °C

Half-life in freshwater sediment:

10.8 h

at the temperature of:

12 °C