Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
09 Sep 1991 - 07 Apr 1992
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
very low oxygen concentrations of <5 mg/L, high application rates compared to the environment
Qualifier:
according to guideline
Guideline:
other: BBA (Biologische Bundesanstalt /Federal Biological Research Centre/) Guidelines, Part IV, Section 5-1 (December 1990): Abbaubarkeit und Verbleib von Pflanzenschutzmitteln im Wasser/Sediment-System.
Version / remarks:
1990
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems)
GLP compliance:
yes (incl. QA statement)
Remarks:
Swiss Federal Department of Interior
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
River
- Details on collection: Water was sampled down to a depth of 10 to 30 cm with a plastic container. The sampling site was located about 1 to 2 m from firm land. After reception in the laboratory, the containers were kept at room temperature until sieving.
- Temperature (°C) at time of collection: 17.1°C
- pH at time of collection: 7.8-7.9
- Redox potential (mv) initial/final: 247, 225 mV
- Hardness (CaCO3): 10


Pond
- Details on collection : Water was sampled down to a depth of 10 to 30 cm with a plastic container. The sampling site was located about 1 to 2 m from firm land. After reception in the laboratory, the containers were kept at room temperature until sieving.
- Temperature (°C) at time of collection: 12.8°C
- pH at time of collection: 7.0-7.53
- Redox potential (mv) initial/final: 215, 59 mV
- Hardness (CaCO3): 21

Details on source and properties of sediment:
River sediment

- Details on collection: The sediment was collected with a plastic shovel from the top 5 to 10 cm of each system (river, pond)
- Textural classification (i.e. %sand/silt/clay):
Clay: 4.5%
Sand: 79.3%
Silt: 16.2%
- pH at laboratory: 7.39
- Redox potential (mv) initial/final: -114 (sampling site), -158 mV (end)
- CEC: 4.48 mVal N/100 g soil
- Biomass: 26.8 mg microbial C/100 mg dry soil

Pond sediment

- Details on collection: The sediment was collected with a plastic shovel from the top 5 to 10 cm of each system (river, pond)
- Textural classification (i.e. %sand/silt/clay):
Clay: 18.4%
Sand: 40.8%
Silt: 33.6%
- pH at laboratory: 7.08
- Redox potential (mv) initial/final: -417 (sampling site), -255 mV (end)
- CEC: 13.73 mVal N/100 g soil
- Biomass: 173.1 mg microbial C/100 mg dry soil
Duration of test (contact time):
101 d
Initial conc.:
1.195 other: mg 14C Thiram/L water
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Test solutions: The maximal recommended field rate for THIRAM application was 3.2 kg a.i./ha. The target application rate was then 1.1 mg 14C-THIRAM per litre water. Two application solutions were prepared, because the samplings at 0 and 6 hours were performed at the same day and the additional sampling was performed after 4 days. The labelled test item was dissolved in 5 mL acetone to prepare the first application solution and in 4 mL acetone to prepare the second application solution. The content of radioactivity was determined by LSC to be 1.295 x 109 and 1.062 x 109 dpm for the first and the second application, respectively. Based on the specific radioactivity of 71 µCi/mg, the amount of 14C-THIRAM was found to be 8.22 mg in 5 mL acetone (1st application) and 6.74 mg in 4 mL acetone (2nd application). 160 µL of application solution I and 180 µL of application solution II corresponding to 0.263 mg/flask (1.195 mg/L) and 0.3032 mg/flask (1.378 mg/L), respectively, were applied per each metabolism flask.
In the first application 1.195 mg of test item per litre water were added to both systems in duplicate for sampling days 0.25, 1, 2, 7, 14, 30 and 57. The second application was performed for sampling days 0, 4 and 101 with 1.378 mg 14C-THIRAM/L water. The results obtained for the samples of the second application were normalised to achieve the first application rate.
- Sample preparation: Water-sediment samples were prepared for the study by sieving (2 mm mesh, sediment), filtering (0.2 mm, water) and pre-incubation under humidified air at 20 ± 2.0°C in the dark to establish aerobic conditions. For each time interval duplicate test system flasks were prepared.
- Test temperature: Aerobic incubation at 20 ± 2 °C, darkness

TEST SYSTEM
Before used, the water was filtered through a 0.2 mm sieve and the sediment was sieved through a 2.0 mm screen. The sieved sediments were stored overnight at 4°C, whereas the prepared water was kept at room temperature and aerated above the surface. Thereafter 220 mL of river water as well as of pond water, 140 g of wet river sediment and 158 g of wet pond sediment corresponding to 93.8 g and 91.6 g dry weight, respectively, were filled into 500 mL all-glass metabolism flasks (please see also Figure A7_1_2_2_2-3).
The study was run in duplicate. The flasks for each sampling interval were incubated in an air-conditioned room at 20 ± 2°C in the dark.
Each water-sediment test system was aerated on the water surface using a CO2-free and moistened air stream. During the acclimation period oxygen concentration, pH and redox potential of the water were measured at appropriate intervals. An equilibrium based on measured values was reached after about 18-20 days of incubation.
The target application rate was 1.1 mg 14C-THIRAM per litre water.
A pre-test was conducted to evaluate the trapping solvents, sampling methods as well as to assure an appropriate balance of radioactivity.

SAMPLING
- Sampling frequency: 0, 0.25, 1, 2, 4, 7, 14, 30, 57 and 101 days
Compartment:
other: river
DT50:
1.9 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: r2=0.98812, DT90= 6.2 d
Remarks:
Transformaion of the parent compound in the River System
Compartment:
other: river
DT50:
4.03 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C
Compartment:
other: pond
DT50:
1.9 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: r2=0.99253, DT90=6.3 d
Remarks:
Transformaion of the parent compound in the Pond System
Compartment:
other: pond
DT50:
4.03 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C
Details on transformation products:
The parent substance disappeared very rapidly from both river and pond systems. 14C-THIRAM represented less then 6% after only 7 days of incubation. The parent substance was not detected in any of the later sampling intervals, showing that 14C-THIRAM is rapidly degraded or adsorbed to the sediment.
14C-THIRAM was degraded mainly to 14CO2 and 14CS2, which reached 65.8% and 60.8% of the applied RA for river and pond systems, respectively, over the incubation period of 101 days.
Additional amounts of 14CO2 and 14CS2 were also detected in the water phase and in the sediment extracts. The maximal amount of 14CO2 detected in the water phase reached 18.1% (river, on day 7) and 19.2% (pond, on day 14) of the applied RA.
Additionally to the volatile compounds, the parent substance was degraded to a very high number of metabolites detected by HPLC. Radioactive fraction M1 represented the major metabolite and was mainly detected in the water phase. This very polar fraction showed the same retention time as the dissolved CS2 in water. The fraction M1 behaved also similarly to the formation of 14CS2 and reached in the river and pond systems a maximum concentration of 21.0% (20.6% in water and 0.4% in sediment) and 19.9% (19.2% in water and 0.7% in sediment) of the applied RA, respectively.
One radioactive fraction found mainly in water and two radioactive fractions found mainly in sediment extracts were identified as DMDTC-ME, TMTM and DMDTC, respectively, based on chromatographic comparison to the authentic reference substances. Each of these fractions did not exceed 5.5% of the applied RA.
In addition up to 12 unknown radioactive fractions were detected, but non of these fractions exceeded 10% of the applied RA. The main fractions M18 and M19 reached the maximum values of 7.5% and 9.7% of the applied RA in the river system and 6.3% and 7.2% in the pond system, respectively. These fractions disappeared very rapidly and represent less than 0.1% of the applied RA from day 14 to study termination for both systems.

14C-Thiram is very rapidly degraded, mainly to 14CS2, 14CO2 and to at least 20 minor metabolites, which were further degraded to CO2, other small fractions and disappeared by adsorption to sediment. The continuous formation of 14CO2 and the decrease of the amount of the bound residues in sediment, show that the non-extractable radioactivity is slowly released and further degraded and mineralised. The half-life of Thiram in the river as well as in the pond system was 1.9 days and the DT90 was 6.2 and 6.3 days for river and pond system, respectively.

The rapid conversion to 14CS2 and 14CO2 indicated that Thiram will not persist in aquatic environments.

Validity criteria fulfilled:
yes
Conclusions:
From the results of this study it can be concluded that 14C-THIRAM is very rapidly degraded, mainly to 14CS2, 14CO2 and to at least 20 minor metabolites, which were further degraded to CO2, other small fractions and disappeared by adsorption to sediment.
The continuous formation of 14CO2 and the decrease of the amount of the bound residues in sediment, show that the non-extractable radioactivity is slowly released and further degraded and mineralised.
The half-live of THIRAM in the river as well as in the pond system was 1.9 days and the DT90 was 6.2 and 6.3 days for river and pond system, respectively.
The rapid conversion to 14CS2 and 14CO2 indicated that THIRAM will not persist in aquatic environments.

Executive summary:

Materials and methods: The objective of the study was to provide information on the distribution and metabolism of 14C-THIRAM in two different water/sediment systems under aerobic conditions according to BBA (Biologische Bundesanstalt /Federal Biological Research Centre/) Guidelines, Part IV, Section 5-1 (December 1990): Abbaubarkeit und Verbleib von Pflanzenschutzmitteln im Wasser/Sediment-System.

A water-sediment test systems was sampled from the river Rhine (Mumpf Zeltplatz, Aargau/Switzerland) and from the pond Judenweiher (Rheinfelden near Görbelhof, Aargau/Switzerland).
The study was performed in 0,5 L all-glass metabolism flasks. The water was filtered through a 0.2 mm sieve and the sediment was sieved through a 2.0 mm screen. The study was run in duplicate. The treated samples as well as the controls were prepared and incubated at 20 ± 2°C in the dark under aerobic conditions.

Each river and pond water-sediment system prepared for sampling on days 0.25, 1, 2, 7, 14, 30 and 57 was treated with 14C-THIRAM in concentration of 1.195 mg/L water. The test systems prepared for sampling on days 0, 4 and 101 were treated with 1.378 mg 14C-THIRAM/L water.
The results obtained for the samples of the second application were normalised to achieve the first application rate.

Water, sediment and volatile substances were worked up and analysed by High Performance Liquid Chromatography (HPLC).

Results and discussion: Radioactivity (RA) in the river and pond test system:

After treatment, the radioactivity (RA) in the river water as well as in the pond water decreased steadily from 107.5% of the applied RA on day 0 to 6.5% and 6.1% on day 101, respectively.

In the sediment the RA first increased up to a maximum of 29.6% (river) and 34.7% of the applied RA (pond) on day 14 and on day 30, respectively, then slowly decreased to 15.6% in the river system and to 23.9% of the applied RA in the pond system at the end of the incubation period.

The sediments were extracted with chloroform and with methanol. The extractable RA from sediments was low and increased continuously reaching maximum values of 3.9% for river and 7.5% for pond at days 14 and 30, respectively. Thereafter the extractable RA decreased to values of 1.8% at day 101 of incubation for both systems.

The degradation of 14C-THIRAM to volatile compounds (14CO2and 14CS2), which were trapped in the volatile traps, was very high and reached 65.8% and 60.8% of the applied RA for river and pond system, respectively, at study termination. In the river system the highest volatilisation rate was observed between days 7 and 30. The highest volatilisation rate for pond system was between days 7 and 14.

In the river system 56.1% of the RA applied was detected as 14CO2and 9.6% as 14CS2 in the river at the study termination. Concurrently in the pond system 36.6% and 24.2% of the applied RA were detected as 14CO2and 14CS2, respectively.

The amount of 14CO2 in the NaOH trap was determined after precipitation with aqueous Ba(OH)2 solution. The amount of 14CO2increased with the incubation time and ranged from about 18% to 56% of the RA in the volatile traps of the river system, between days 4 and 14. At the study termination the value of 96% RA was reached. The corresponding values for the pond system ranged from 9% to 23%, respectively. On the last incubation day 97% of the RA was detected. The remaining volatile RA in the NaOH traps was considered to be  14CO2.

Also in the water phase as well as in sediment extracts from both systems volatiles compounds were observed. After precipitation with Ba(OH)2 up to 57.5% (river) and 43.9% (pond) of the initial RA was detected in water as 14CO2.
Total volatiles (in volatile traps and dissolved in water and sediment extracts) amounted to 70.6% and 67.3% of the RA applied at the study termination in the river and pond systems, respectively.

The total mean recoveries of radioactivity obtained during the whole incubation time were 95.6 ± 6.2% and 99.1% ± 6.1% of RA applied for the river and pond systems, respectively.

Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
22 June 1995 - 05 October 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: BBA (Biologische Bundesanstalt /Federal Biological Research Centre/) Guidelines, Part IV, Section 5-1 (December 1990): Abbaubarkeit und Verbleib von Pflanzenschutzmitteln im Wasser/Sediment-System.
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Swiss Department of Home Affairs
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment
Details on source and properties of surface water:
- Details on collection: The water/sediment system was collected from the Rhine river (Sisseln, AG Switzerland). The water was sampled at a depth between 10 to 30 cm, and was transported in containers to the laboratory where it was stored at about 4°C until it was used.
- Temperature (°C) at time of collection: 15.8°C
- pH at time of collection: 8.03
- Redox potential (mv) initial/final: 215,202 mV
- Oxygen concentration initial/final: 10.3-10.1, 5.6-5.1 mg/L
- Hardness (CaCO3): 12
Details on source and properties of sediment:
- Details on collection: The water/sediment system was collected from the Rhine river (Sisseln, AG Switzerland). The sediment was sampled from the top 5 to 10 cm, and was transported in containers to the laboratory where it was stored at about 4°C until it was used.
- Textural classification (i.e. %sand/silt/clay):
Clay: 2.8%
Silt: 5.6%
Sand: 91.6%
- pH at time of collection: 7.35
- Organic carbon (%):
- Redox potential (mv) initial/final: -180, -199- - 275 mV
- CEC : 24.6 mVal N/100 g dry sediment
Duration of test (contact time):
10 d
Initial conc.:
16.26 µg/L
Based on:
act. ingr.
Remarks:
concentration selected based on experience from previous study.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution: A volume of 530 ml of water and 300 g of sediment (wet) were filled into 1 liter metabolism flasks.
- Test solutions: The labelled 14C-THIRAM containing 75 MBq was dissolved in 1 mL acetone. To prepare the application solution, 30 µL were transferred into volumetric flask and diluted with acetone to 10 mL. The content of radioactivity in the application solution was assayed in triplicate by LSC. For this purpose 3 x 50 µL were diluted to 10 mL with acetone and then 1.0 mL per flask was used to determine the radioactivity. Based on this LSC-value (118583556 dpm/10 mL) an application volume of 460 µL was calculated, which correspond to 16.26 µg a.i./L water. The two control flasks were applied with the same volume (460µL) of pure acetone.
- Sample preparation: Water-sediment samples were prepared for the study by sieving (2 mm mesh, sediment), filtering (0.2 mm, water) and pre-incubation under humidified air at 20 ± 2.0°C in the dark to establish aerobic conditions. For each time interval duplicate test systems (30 flasks in total) were prepared. 14 flasks were treated with radiolabeled THIRAM in acetone at a concentration of 16.26 µg a.i./L water, other 14 flasks were used as reserves and the last two as controls.
For sampling at time 0 hour each replicate test system was treated and immediately processed. For further sampling intervals, the test systems were incubated at 20 ± 2.0°C. The flasks were ventilated with CO2-free air directly after treatment. The outgoing stream was passed through three traps containing one empty trap followed by one with 50 ml 1M KOH dissolved in methanol and one ethylene glycol trap (50 ml).
- Test conditions: aerobic incubation at 20 ± 2 °C, darkness
- Other: The system was aerated and the oxygen concentration, pH and redox potential of the water was measured until an equilibration in the system was achieved after about 27 days.

TEST SYSTEM
- Test system: The study was performed in 1 L all-glass metabolism flasks. They were filled with the sediment to a height of about 2.5 cm and with 530 ml water to achieve a water column of about 6 cm.
- Test concentration: The target value was calculated to be 16.0 µg 14C-THIRAM/L water or 8.48 µg active ingredient / 530 mL water (0.0895 MBq/sample, 5367840 dpm/sample, 10.55 MBq/mg specific radioactivity). The test item was applied in acetone (460µL per flask) at actual concentration of 16.26 µg a.i./L water or 8.62 µg a.i. per flask (5454844 dpm/flask)
- Details of trap for CO2 and volatile organics if used: The metabolism apparatus of the aquatic model systems was equipped with a trap containing 1M KOH in methanol (for trapping CO2) and a trap containing ethylene glycol (for trapping volatile organic compounds).

SAMPLING
- Sampling frequency: 0.0, 0.25, 0.75, 2.0, 7.0 and 10.0 days
Compartment:
natural water / sediment: freshwater
DT50:
0.7 d
Type:
(pseudo-)first order (= half-life)
Temp.:
20 °C
Remarks on result:
other: R2=0.9979, DT90= 2.5 d
Compartment:
natural water / sediment: freshwater
DT50:
1.5 d
Type:
(pseudo-)first order (= half-life)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C
Transformation products:
yes
Remarks:
refer to field "Details on transformation products"
Details on transformation products:
Partition of the water-phase indicated that with increasing incubation time more polar fractions appeared and remained in the water phase. Due to the low application rate, a special effort was given to characterize the polar fraction in the water phase labelled as MW. The radioactive fraction MW increased to 42.5% of the initial RA (6.9 µg/L) within 2 days and then decreased to 34.0% (5.5 µg/L) on day 10. This fraction was subsequently separated into at least 9 different unknown radioactive fractions, labelled as MW1 to MW9. None of these fractions could be identified by co-chromatography with a known reference compounds.
The main fraction was MW2, the only fraction which increased to 11.7% of RA applied on day 10. Other fractions reached their maximum value (≤ 8% of RA applied) before or at day 2 of incubation period and either decreased until day 10 or were not detectable.
DMDTC-ME was the only reference compound which was detected on day 7 and 10 with 1.2% and 0.8%, respectively. Another unknown, less polar fraction U was detected once on day 2 in the organic partition by HPLC and reached 1.2% of RA applied.
Evaporation of parent compound:
no
Volatile metabolites:
no
Remarks:
CO2 and CS2
Residues:
not specified

RECOVERY OF RADIOACTIVITY

The mean recovery of radioactivity applied was 94.9 ± 2.9%.The individual recoveries were all between 92 and 101.5%.

- Radioactivity in water: The level of radioactivity decreased very fast from 99.7% of applied radioactivity on day 0 to 35.2% on day 10.

- Radioactivity in sediment: The level of radioactivity first increased from 0.6% on day 0 to 33.4% on day 7. It decreased slightly to 32.6% on day 10.

- Volatile substances: No measurement was performed on day 0. Volatile radioactivity (including the 14CO2 dissolved in the water-phase) increased within the first day to 13.1% on day 2, to 23.6% on day 7 and to 25.7% at the end of the study. Non-14CO2 radioactivity resulted in 4.7% of the radioactivity applied, whereas 14CO2 accounted for 9.6%. The non-14CO2 radioactivity was considered to consist mainly of 14CS2 in analogy with the former study (RCC project number 303456), but could not be confirmed in this study because of the low concentration of the substance tested. Mineralisation started after day 2. The amount of 14CO2 in the test system at the end of the study was 21.0%.

DEGRADATION

In the main test thiram degraded fast in water from 96.7% on day 0 to 0.5% on day 10, which was just above the determination limit in this study. The degradation rate of thiram was calculated using a first order kinetic model and the optimum fit found. The DT-50 value was 0.7 days and the DT-90 (90% degradation) value was 2.5 days. The calculted level of Thiram was 0.01% er 0.0016 µg/L on day 10.

METABOLITES

Refer to section "Details on transformation products" and attachment.

For more details on distribution and recovery of radioactivity, pattern of radioactive fractions and mineralization refer to the attachment.


In a pre-test two flasks were treated with 14C-thiram to test the application and the extraction procedures. The results confirmed the applicability of the methods and showed that a sampling interval of 18 hours would be closer to the DT50 value than 24 hours and it was changed accordingly for the main study.

Validity criteria fulfilled:
yes
Conclusions:
From the results of this study it can be concluded that under aerobic conditions THIRAM is very fast degraded to several polar minor metabolites and then mineralised to CO2.
The half-life of THIRAM was 0.7 days and the DT90 was 2.5 days.
Executive summary:

Materials and methods: The objective of the study was to provide information on the distribution and metabolism of 14C-THIRAM in water/sediment systems according to BBA (Biologische Bundesanstalt /Federal Biological Research Centre/) Guidelines, Part IV, Section 5-1 (December 1990): Abbaubarkeit und Verbleib von Pflanzenschutzmitteln im Wasser/Sediment-System.

A water-sediment test system was sampled from the river Rhine (Sisseln, AG / Switzerland).
The study was performed in an open gas-flow-system in 1.0 L all-glass metabolism flasks. The water was filtered through a 0.2 mm sieve and the sediment was sieved through a 2.0 mm screen. The study was run in duplicate. 14 flasks with treated samples, 14 untreated flasks as reserves and 2 controls were prepared and incubated at 20 ± 2°C in the dark. Each water/sediment test system was treated with 460 µL of the radiolabelled 14C-THIRAM in acetone. The actual radioactivity of the application solution was 5454844 dpm per flask. The test item was applicated at actual concentration of 16.26 µg a.i./L water or 8.62 µg a.i. per flask. Water, sediment and volatile substances were worked up and analysed by HPLC and TLC.

Results and discussion: 14C-THIRAM was detected with 96.7% of the radioactivity applied (15.7 µg a.i./L) in the river water directly after treatment on day 0. This amount rapidly decreased to 51.6% (8.4 µg/L) on day 0.75 and was just slightly above the determination limit of 0.3% on day 10. Only 0.5% of applied RA (0.08 µg/L) was detected at the study termination.

The rate of degradation was calculated according to 1st-order kinetic model. 0.7 and 2.5 days were obtained for DT50 and DT90, respectively. In water phase the level of radioactivity decreased very fast from 99.7% of applied radioactivity (16.2 µg parent equivalents per litre water) on day 0 to 25.2% (5.7 µg/L) on day 10. In sediment samples the radioactivity first increased from 0.6% (0.1 µg/L) on day 0 to 33.4% (5.4 µg/L) on day 7. Afterwards a slight decrease of RA up to 32.6% (5.3 µg/L) on day 10 was observed. The water phase was partitioned twice with dichloromethane. The RA in the dichloromethane phase decreased steadily to 5% at the end of the study. The radioactivity remaining in the water phase increased until day 2 to > 40% of the RA applied, but decreased thereafter until day 10 to about 30%. Volatile RA, including the 14CO2 dissolved in the water phase increased continuously during the incubation time. Within the first day the RA increased to 13.1% (2.1 µg parent equivalents per litre). Afterwards 23.6% of applied RA (correspond to 3.8 µg/L) were detected on day 2 and at the study termination 25.7% (4.2 µg/L).
No RA was found in the ethylene glycol traps. The radioactivity was retained in the 1M KOH in methanol and consisted mainly of 14CO2. The amount of 14CO2 in the test system at the end of the study was 21.0% of the RA applied. At the same time other volatile substances reached only 4.7% (due to information of a former study probably 14CS2). The mean recovery of radioactivity was 94.9 ± 2.9% of RA applied (15.4 ± 0.5 µg parent equivalents per L water). The individual recoveries were all between 92.0 and 101.5%.

Endpoint:
biodegradation in water: simulation testing on ultimate degradation in surface water
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 Dec 2013 - 10 Feb 2014
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
see validity criteria
Qualifier:
according to guideline
Guideline:
OECD Guideline 309 (Aerobic Mineralisation in Surface Water - Simulation Biodegradation Test)
Version / remarks:
2004
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on source and properties of surface water:
- Details on collection: Surface water was obtained from the River Ouse on 09 December 2013.
- Storage conditions: The surface water was used within 1 day of collection.
- Temperature (°C) at time of collection: 6.3 °C
- pH at time of collection: 8.01
- Oxygen concentration (mg/l) initial/final: 7.72/9.94
- Hardness (CaCO3): 392 mg/L
- Total organic carbon (mg/L): 6.7
- Dissolved organic carbon: 6.7%
- Biological oxygen demand: 3 mg/L
- Total nitrogen: 12.6 mg/L
- Total suspended solids: < 10 mg/L
- Biomass (cfu/g) at day 0: Aerobic bacteria: 1.49 x 10³, aerobic bacterial spores: 4.05 x 10², actinomycetes: 2, fungi: 3
- Water filtered: yes
- Type and size of filter used, if any: Upon receipt at the testing facility and prior to use, the surface water was passed through a 0.2 mm sieve and a coarse filter paper (GF/A).
Duration of test (contact time):
62 d
Initial conc.:
2 µg/L
Based on:
test mat.
Initial conc.:
10 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
test mat. analysis
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment: 100 mL
- Test temperature: 20 ± 2 °C
- pH: 8.30 - 8.84
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Cylindrical 500 mL glass bottles, incubated in a dark and temperature-controlled room with 100 mL surface water.
- Number of culture flasks/concentration: Triplicate vessels (named FT) of treated surface water were taken for analysis at each sampling interval (two of the vessels were analysed by HPLC for test substance and degradation products and a single vessel was used for measurement of 14CO2 and 14CS2).
- Method used to create aerobic conditions: continuous stirring, sufficient air was drawn through each to allow gas flow
- Details of trap for CO2 and volatile organics if used: The following traps were used:
Trap 1: containing ethyl digol (to trap volatile organic compounds)
Trap 2: containing 1 M methanolic potassium hydroxide solution with phenolphthalein indicator (to trap 14CS2)
Trap 3, containing 1 M aqueous potassium hydroxide solution with phenolphthalein indicator (to trap 14CO2)
The flow-through system of the samples treated with 14C-sodium benzoate were equipped with 1x Trap 1 and 2x Trap 3.
Other: In addition one additional sample set up for mass balance determination was incorporated into an individual flow-through system equiped with 1x Trap 1, 2x Trap 3, a furnace containing catalytic convertor and then 2x Trap 3 again to trap any 14CO2 generated by the catalyst.

SAMPLING
- Sampling frequency: For each concentration of test substance, duplicate samples of surface water were taken for analysis immediately (time zero samples). Triplicate samples of surface water were analysed after 2, 4 and 6 hours and 1, 2, 3, 6, 14, 30 and 62 days of incubation.
- Sampling method used per analysis type: Two vessels were analysed by HPLC for test substance and degradation products and a single vessel was used for direct measurement of 14CO2 and 14CS2 (weighed aliquots, 1.0 mL).

DESCRIPTION OF CONTROL AND/OR BLANK TREATMENT PREPARATION
CONTROL AND BLANK SYSTEM
- Blank flasks: 2 blank flasks containing no test substance.
- Abiotic sterile control: 2 flasks sterilised by autoclaving (121 °C, 20 minutes), prior to addition of test substance.
- Positive control: 2 flasks containing the reference substance 14C-sodium benzoate at 10 μg/L.
- Other: Three vessels of surface water were set up for microbiological activity measurements and two vessels were assigned to provide background counts for liquid scintillation counting (LSC) and were used for system parameter measurements (pH and oxygen content). These vessels were not treated with the test substance.
- Other: For direct 14CO2/14CS2 determination the weight of the surface water was recorded and duplicate weighed aliquots (1.0 mL) taken for radioassay. The water was re-weighed and acidified (conc. HCl to pH 2/3) before the vessel was reconnected to a flow through system of traps (as detailed in section 2.5.1 and refilled with fresh media). After approximately 2 hours the vessel was removed and the weight of the water was recorded and duplicate weighed aliquots (1.0 mL) taken for radioassay. The volumes of trapping solutions taken before and after acidification were measured and duplicate (1.0 mL) aliquots taken for radioassay.
Reference substance:
benzoic acid, sodium salt
Remarks:
14C labelled; 10 µg/L
Compartment:
natural water: freshwater
% Recovery:
100.4
Remarks on result:
other: Timepoint 0
Remarks:
2 µg/L dose level
Compartment:
natural water: freshwater
% Recovery:
84.3
Remarks on result:
other: After 62 d
Remarks:
2 µg/L dose level
Compartment:
natural water: freshwater
% Recovery:
101.6
Remarks on result:
other: Timepoint 0
Remarks:
10 µg/L dose level
Compartment:
natural water: freshwater
% Recovery:
64.3
Remarks on result:
other: After 62 d
Remarks:
10 µg/L dose level
Compartment:
natural water: freshwater
DT50:
0.13 d
Type:
other: Double first order in parallel (DFOP)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
DT50 of parent compound; spike level 2 µg/L
Compartment:
natural water: freshwater
DT50:
0.28 d
Type:
other: Double first order in parallel (DFOP)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C, spike level 2 µg/L
Compartment:
natural water: freshwater
DT50:
0.14 d
Type:
other: Double first order in parallel (DFOP)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
DT50 of parent compound; spike level 10 µg/L
Compartment:
natural water: freshwater
DT50:
0.3 d
Type:
other: Double first order in parallel (DFOP)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C, spike level 10 µg/L
Transformation products:
yes
Remarks:
refer to field "Details on results incl. tables"
Details on transformation products:
- Pathways for transformation: The proposed pathway for the biotransformation of thiram in surface water is that the substance transforms to CS2 directly and to CO2 through unstable degradates.
- Formation and decline of each transformation product during test: refer to attachment
- Maximum occurrence of each transformation product: refer to attachment
Evaporation of parent compound:
no
Volatile metabolites:
yes
Remarks:
CO2 and CS2
Residues:
no
Details on results:
HPLC analysis of the surface water resolved up to ten unknown components in addition to thiram. The amount of thiram, after treatment at the 2 µg/L nominal concentration, in the surface water declined rapidly from a mean of 97.7% AR at time zero to a mean of 34.0% after 6 hours of incubation. The amount of thiram, after treatment at the 10 µg/L nominal concentration, in the surface water declined rapidly from a mean of 100.9% AR at time zero to a mean of 7.3% AR after 2 days of incubation.

MAJOR TRANSFORMATION PRODUCTS
- 2 µg/L concentration: One unknown degradate was present at levels greater than 10% in one or more samples. Due to the unstable nature of these components identification was not achieved.
- 10 µg/L concentration: Six unknown degradates were present at levels greater than 10% in one or more samples. Due to the unstable nature of these components identification was not achieved.

Based on the HPLC results obtained, it was concluded that thiram and other degradation products degraded to form the major degradate, component 2. Extensive efforts were made to isolate and identify component 2. This work was not successful within the scope of this study.

Microbiology:

The total recoveries of radioactivity in the surface water treated with the reference substance 14C sodium benzoate were 94.0 – 102.6% applied radioactivity after 14 days. The volatile radioactivity, was all associated with 14CO2, accounted for 84.3 to 91.2% of the applied radioactivity after 14 days. Since the reference substance was degraded within the expected time frame, it was concluded that the surface water was microbilogically active and the test is valid. For more details see respective table under attachments.

 

Incubation Conditions:

The oxygen content was between 6.4 and 9.94 mg/L (69 and 97% of saturation). The pH was between 8.3 and 8.84. 

 

Recoveries:

1. Samples for chromatographic analysis: The total recoveries of radioactivity from the samples were 63.2 – 102.9% applied radioactivity (AR).

2. Samples for direct 14CO2/14CS2 determination:

- The initial total recoveries of radioactivity from the 2 µg/L nominal concentration samples in the main experiment declined from 101.0% AR at 2 hours to 41.3% AR at day 62. Volatile radioactivity, probably associated with both 14CO2 and 14CS2 (captured in the methanolic potassium hydroxide traps) was detected from day 14 onwards and accounted for a maximum of 27.4% AR at day 62. After stripping off volatile radioactivity (14CO2/14CS2) at the 2 µg/L nominal concentration, total radioactivity in the surface water declined from 87.6% AR at 2 hours to a mean of 15.5% AR after 62 days. Direct volatile radioactivity (14CO2/14CS2, captured in the methanolic potassium hydroxide traps) accounted for a maximum of 13.0% AR after 6 days. 

- The initial total recoveries of radioactivity from the 10 µg/L nominal concentration samples in the main experiment declined from 98.0% AR at 2 hours to 39.3% AR at day 62. Volatile radioactivity, probably associated with both 14CO2 and 14CS2 (captured in the methanolic potassium hydroxide traps), was detected from day 1 onwards and accounted for a maximum of 15.1% AR at day 3. After stripping off volatile radioactivity (14CO2/14CS2) at the 10 µg/L nominal concentration samples, total radioactivity in the surface water declined from 88.1% AR at 2 hours to a mean of 20.8% AR after 62 days. Direct volatile radioactivity (14CO2/14CS2, captured in the methanolic potassium hydroxide traps) accounted for a maximum of 10.4% AR after 6 days.

 

Setup with catalytic converter:

It was considered that the low recovery of radioactivity was due to losses of volatile radioactivity, primarily 14CS2. One sample was connected to a catalytic converter in order to improve the recovery.

Transformation products:

Refer to field "Details on transformation products" and to attached document.

The initial total recovery was 80.1% AR, with volatile radioactivity (14CO2, captured in the aqueous potassium hydroxide traps) accounting for 42.4% AR. Additionally 15.5% AR was recovered as 14CO2 after conversion of 14CS2 on the catalyst. After stripping off volatile radioactivity (14CO2/14CS2) the initial total recovery in the surface water was 22.4% AR, with no further volatile radioactivity detected. The presence of CS2 was confirmed by GC/MS chromatography in samples set up specifically for this analysis. The presence of14CO2in the traps associated with the catalytic converter was confirmed by precipitation with barium chloride. It is considered that both 14CO2 and 14CS2 were captured in the methanolic potassium hydroxide traps. Although no radioactivity was captured in the aqueous potassium hydroxide traps attached to the test vessels, the production of both 14CO2 and 14CS2 were confirmed. The low recoveries were probably due to loss of 14CS2. 

 

For further details on surface water sampling information, physical and chemical characteristics of the surface water, microbiological characterisation of surface water, recoveries and distribution of radioactivity from incubated surface water treated with the test substance [14C]-thiram and with the reference substance 14C-sodium benzoate and kinetic data see attachment.

Table 1: Validity criteria for OECD 309

Criterion from the guideline

Outcome

Validity criterion fulfilled

Reference substance should be degraded within the expected time interval (for

sodium benzoate, usually less than two weeks).

84.3 – 91.2% volatile 14CO2 after 14 d

yes

The total recovery (mass balance) at the end of the experiment should be between 90% and 110%

for radiolabelled substances.

64.3 - 84.3 after 62 d

No

It was considered that the low recovery of radioactivity was due to losses of volatile radioactivity, primarily 14CS2. In order to try to improve the recovery one additional sample treated at 10 µg/L was connected to a catalytic converter, which confirmed the hypothesis. Therefore the study is considered acceptable.

Validity criteria fulfilled:
yes
Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
05 Dec 2013 - 24 Jun 2014
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:
2002
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.4300 (Aerobic Aquatic Metabolism)
Version / remarks:
2008
Qualifier:
according to guideline
Guideline:
other: FOCUS: Guidance document on estimating persistence and degradation kinetics from environmental fate studies on pesticides in EU registration. Report of the FOCUS Work Group on Degradation Kinetics, EC Document Reference Sanco/10058/2005, version 2.0
Version / remarks:
2006
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water / sediment: freshwater
Details on source and properties of surface water:
- Storage conditions: 4°C
- pH at time of collection: Abbey Lake: 8.2, Swiss Lake: 7.2
- Organic carbon (ppm): Abbey Lake: 9.2, Swiss Lake: 6.2
- Electrical conductivity (mmhos/cm): Abbey Lake: 0.32, Swiss Lake: 0.09
- Hardness (mg equivalent CaCO3/L): Abbey Lake: 158, Swiss Lake: 24
- Total Suspended Solids (ppm): Abbey Lake: 10, Swiss Lake: 8
- Alkalinity (mg CaCO3/L): Abbey Lake: 122, Swiss Lake: 7
Details on source and properties of sediment:
- Storage conditions: 4°C
- Textural classification (i.e. %sand/silt/clay): Abbey Lake: silt loam, Swiss Lake: sand
- pH at time of collection: Abbey Lake: 7.6, Swiss Lake: 6.6
- Organic carbon (%): Abbey Lake: 5.1, Swiss Lake: 0.9
- Biomass (in μg C/g at start): Abbey Lake: 1336.9, Swiss Lake: 475.0
- Sediment samples sieved: yes, using a 2 mm mesh sieve prior to analyses and acclimation.
- Bulk Density (disturbed), g/cc: Abbey Lake: 0.62, Swiss Lake: 1.08
- Cation exchange capacity, meq/100 g: Abbey Lake: 9.1, Swiss Lake: 3.1

Duration of test (contact time):
60 d
Initial conc.:
100 µg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Details on study design:
TEST CONDITIONS
- Volume of test solution/treatment: 50 g dw sediment
- Test temperature: 20°C ±2°C
- Continuous darkness: yes
- Other: <0.1% of co-solvent per sample (mL/g X 100%)
- Acclimation: The water/sediment systems were acclimated and incubated at 20°C + 2°C under darkness for 21 d.

TEST SYSTEM
- Culturing apparatus: 250 or 500 mL size glass bottles set-up in series
- Number of culture flasks/concentration and sampling interval: 2
- Method used to control oxygen conditions: moist air flow through system under vacuum
- Details of trap for CO2 and volatile organics if used: One trap of ethylene glycol (for organic volatiles) followed by two 1N NaOH traps through a catalytic converter into two 1N NaOH traps (for CO2) were used.

SAMPLING
- Sampling frequency: 0, 0.04, 0.08, 0.21, 1, 6, 13, 39 and 60 Days

DESCRIPTION OF CONTROL AND/OR BLANK TREATMENT PREPARATION
CONTROL AND BLANK SYSTEM
- Other: Abbey Lake and Swiss Lake control samples without test item

Compartment:
natural water / sediment: freshwater
% Non extractable:
56.17
% CO2:
24.12
% Other volatiles:
1.35
% Recovery:
93.89
Remarks on result:
other: Abbey Lake, Day 60
Remarks:
Other volatiles: CS2 and VOC
Compartment:
natural water / sediment: freshwater
% Non extractable:
45.2
% CO2:
32.21
% Other volatiles:
8.64
% Recovery:
99.06
Remarks on result:
other: Swiss Lake, Day 60
Remarks:
Other volatiles: CS2 and VOC
Parent/product:
parent
Compartment:
sediment
% Degr.:
99.44
Parameter:
test mat. analysis
Sampling time:
60 d
Remarks on result:
other: Abbey Lake
Parent/product:
parent
Compartment:
water
% Degr.:
100
Parameter:
test mat. analysis
Sampling time:
60 d
Remarks on result:
other: Abbey Lake
Parent/product:
parent
Compartment:
sediment
% Degr.:
100
Parameter:
test mat. analysis
Sampling time:
60 d
Remarks on result:
other: Swiss Lake
Parent/product:
parent
Compartment:
water
% Degr.:
100
Parameter:
test mat. analysis
Sampling time:
60 d
Remarks on result:
other: Swiss Lake
Key result
Compartment:
natural water / sediment: freshwater
DT50:
0.14 d
Type:
other: Modified first order multi-compartment (FOMC)
Temp.:
20 °C
Remarks on result:
other: Abbey Lake, total system persistence endpoint
Remarks:
Best fit after reevaluation based on FOCUS
Key result
Compartment:
natural water / sediment: freshwater
DT50:
0.3 d
Type:
other: Modified first order multi-compartment (FOMC)
Temp.:
12 °C
Remarks on result:
other: Abbey Lake, total system persistence endpoint
Remarks:
Best fit after reevaluation based on FOCUS; Calculated DT50 of the parent compound, based on results at 20 °C
Key result
Compartment:
natural water / sediment: freshwater
DT50:
0.129 d
Type:
other: Single First Order kinetics (SFO)
Temp.:
20 °C
Remarks on result:
other: Swiss Lake, total system persistence endpoint
Remarks:
Best fit after reevaluation based on FOCUS
Key result
Compartment:
natural water / sediment: freshwater
DT50:
0.27 d
Type:
other: Single First Order kinetics (SFO)
Temp.:
12 °C
Remarks on result:
other: Swiss Lake, total system persistence endpoint
Remarks:
Best fit after reevaluation based on FOCUS; Calculated DT50 of the parent compound, based on results at 20 °C
Compartment:
natural water / sediment: freshwater
DT50:
0.16 d
Type:
other: double first order kinetics (DFOP)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Transformation of parent compound in the Abbey Lake System; kinetic model with best fit
Compartment:
natural water / sediment: freshwater
DT50:
0.34 d
Type:
other: double first order kinetics (DFOP)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound in the Abbey Lake System, based on results at 20 °C
Compartment:
natural water / sediment: freshwater
DT50:
0.14 d
Type:
other: Modified first order multi-compartment (FOMC)
Temp.:
20 °C
Remarks on result:
other:
Remarks:
Transformation of parent compound in the Swiss Lake System; kinetic model with best fit
Compartment:
natural water / sediment: freshwater
DT50:
0.3 d
Type:
other: Modified first order multi-compartment (FOMC)
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound in the Swiss Lake System, based on results at 20 °C
Transformation products:
yes
Remarks:
For further details refer to "Details on transformation products" and attachment
No.:
#1
Details on transformation products:
- Formation and decline of each transformation product during test: Only one major radioactive component detected by HPLC exceeded 5% AR and was identified as DMCS in the total system and all other components detected in the water fraction were minor residues. CS2 was a minor volatile metabolite in both systems, reaching a maximum of 1.3 and 5.5 % of the applied dose for Abbey Lake and Swiss Lake, respectively. For both the Abbey Lake and Swiss Lake systems, carbon dioxide was a major volatile metabolite, reaching maximums of 24.1 and 32.2% of the applied dose by the end of the incubation, respectively.
- Pathways for transformation: 14C-Thiram was rapidly degraded (completely degraded by Day 6 in both systems) to the metabolite DMCS as well as other minor components. In addition, 14CO2 and 14CS2 were observed along with a significant amount of bound residues during the study period.
- Maximum occurrence of each transformation product: DMCS accounted for a maximum of 39.9% AR and 61.8% AR for Abbey Lake and Swiss Lake, respectively.
Evaporation of parent compound:
no
Volatile metabolites:
yes
Remarks:
CS2, CO2
Residues:
yes
Details on results:
TEST CONDITIONS
- Aerobicity (or anaerobicity), moisture, temperature and other experimental conditions maintained throughout the study: yes, Abbay Lake: pH: 6.89 - 7.36, Dissolved Oxygen: 6.01 - 7.18 mg/L, Oxidation-Reduction Potential: 201.4 - 213.8 mV (water) and 166.8 - 184.8 mV (Sediment); Swiss Lake: pH: 6.81 - 7.17, Dissolved Oxygen: 6.45 - 9.3 mg/L, Oxidation- Reduction Potential: 214.5 - 223.9 mV (water) and 135.6 - 171.5 mV (sediment)

MAJOR TRANSFORMATION PRODUCTS
- Maximum concentrations in % of the applied amount and day(s) of incubation when observed: Abbey Lake: 39.88% DMCS on Day 1 in the water fraction, Swiss Lake: 61.8% on Day 6 in the water fraction
- Range of maximum concentrations in % of the applied amount at end of study period: Abbey Lake: 5.95% on Day 60 in the water fraction, Swiss Lake: 9.2% on Day 60 in the water fraction

MINOR TRANSFORMATION PRODUCTS
- Range of maximum concentrations in % of the applied amount and day(s) of incubation when observed: please refer to attached document
- Range of maximum concentrations in % of the applied amount at end of study period: please refer to attached document

TOTAL IDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT: 93.89% in Abbey Lake on Day 60, 99.06% in Swiss Lake on Day 60

NON-EXTRACTABLE RESIDUES
- % of applied amount at day 0: 0.74% - 1.8%
- % of applied amount at end of study period: 45.2% - 56.17%

MINERALISATION
- % of applied radioactivity present as CO2 and CS2 at end of study: Abbey Lake: 25.42%, Swiss Lake: 37.67%

VOLATILIZATION
- % of the applied radioactivity present as volatile organics at end of study: 0.05% - 3.18%

After the final sampling interval, the microbial biomass were determined to be 1336.9 and 259.6 µg/g for the Abbey Lake and Swiss Lake sediments, respectively. These results confirmed that the both sediments were microbially viable during the course of the study.

Further kinetic results are provided in the attachment below.

Table 1: Quality criteria for OECD 308

Criterion from the guideline

Outcome

quality criterion fulfilled

Recoveries should

range from 90% to 110% for labelled chemicals and from 70% to 110% for non-labelled chemicals.

 90.6 - 104%

 yes

The reevaluation of the results based on FOCUS (2006) with respect to persistence showed for Thiram that the FOMC model was more appropriate for the data of Abbay Lake and the SFO kinetics described better the degradation of the substance based on the data of the Swiss Lake. Therefore the key DT50 values were 0.14 d for Abbey Lake and 0.129 d for the Swiss Lake. Further results and details of the retrospective kinetic assessment are presented in the attachment provided below.


Validity criteria fulfilled:
yes
Remarks:
For details refer to field "Any other information on results incl. tables"
Endpoint:
biodegradation in water: sediment simulation testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
15 Feb 1993 - 18 Feb 1994
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EPA Subdivision N Pesticide Guideline 162-3 (Anaerobic Aquatic Metabolism)
Version / remarks:
1982
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
yes
Oxygen conditions:
anaerobic
Inoculum or test system:
natural water / sediment: freshwater
Duration of test (contact time):
252 d
Initial conc.:
12.254 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
radiochem. meas.
Compartment:
natural water / sediment: freshwater
DT50:
4.25 d
Type:
other: 1.5-order
Temp.:
20 °C
Remarks on result:
other:
Remarks:
DT50 of the parent compound
Compartment:
natural water / sediment: freshwater
DT50:
9.02 d
Type:
other: 1.5-order
Temp.:
12 °C
Remarks on result:
other:
Remarks:
Calculated DT50 of the parent compound, based on results at 20 °C
Transformation products:
yes
No.:
#1

The main metabolite was CS2, which appeared very fast mainly within the first 14 days and then reached 77.5 % applied radioactivity after 252 days. Another important degradation product was CO2, which appeared after day 7 and reached 15.8 % at day 252. Three other non-identified metabolites (M6, M8 and M9) were of minor importance.

Description of key information

-       DT50 of parent substance in surface water: 0.13 – 0.16 days at 20 °C based on test material analysis (recalculated to 0.28 – 0.34 d at 12°C, aerobic, OECD 309, natural river water).

-       58% of AR mineralization after 62 d (only in sample connected to a catalytic converter, however low recoveries).

 

-       DT50 of parent substance in water/sediment: 0.129 – 0.14 days at 20 °C based on test material analysis (recalculated to 0.27 – 0.3 d at 12°C, aerobic, BBA Part IV Section 5-1, natural water/sediment system)

-       24.42 and 37.67% of AR mineralization after 60 days.

Key value for chemical safety assessment

Additional information

Five studies investigating the transformation of tetramethylthiuram disulfide (CAS No. 137-26-8) in natural water and water/sediment systems are available.

 

In the first key study (2015), the degradation and metabolism of 14C-thiram was investigated in a simulation study performed according to the OECD Guideline No. 309 and GLP. The degradation of 2.0 and 10.0 µg/L radiolabeled parent substance was investigated in natural river water incubated for 62 d in the dark under aerobic conditions at a temperature of 20 °C. Duplicate vessels were analysed for test substance and degradation products by HPLC. Treated samples were additionally used for the direct measurement of volatile degradation products and were incubated in air flow systems for 62 d. Mean recoveries of samples for the HPLC analysis were low and laid at 84.3 % AR (2 µg/L sample) and 64.3 % AR (10 µg/L) after 62 days. The surface water samples at the 2 µg/L nominal concentration, where volatile radioactivity (14CO2 and 14CS2) was stripped off, showed a decline in total radioactivity in solution over the time course from 87.6% AR at 2 hours to a mean of 15.5% AR after 62 days. Direct volatile radioactivity (14CO2 and 14CS2) accounted for a maximum of 13% AR after 6 days (n.d. after 62 d). The surface water samples at the 10 µg/L nominal concentration, where volatile radioactivity (14CO2 and 14CS2) was stripped off, showed a decline in total radioactivity in solution over the time course from 88.1% AR at 2 hours to a mean of 21.2% AR after 62 days. Direct volatile radioactivity (14CO2 and 14CS2) accounted for a maximum of 10.4% AR after 6 days (5.4% after 62 d). Since the recoveries were low one sample was connected to a catalytic converter in order to improve the system. The mass balance for this sample was 80.4% AR after 62 days and the 14CO2 accounting for 42.4% AR. This suggests that mineralisation to CO2 does occur. The disappearance times (DT50 and DT90) of thiram in surface water were calculated by nonlinear regression and the best fits were based on the Simple First Order kinetic model and the Double First Order in Parallel model. Based on test material analysis, thiram in surface water treated at 2 µg/L and 10 µg/L degraded rapidly under aerobic conditions with DT50 values of 0.13 - 0.14 days and 0.14 – 0.16 days (0.28 – 0.3 and 0.3 – 0.34 days, recalculated to 12 °C), respectively. CS2 and CO2 were the major degradants. Thiram was degraded to up to further ten components, which despite extensive efforts, due to their instability, it was not possible to identify their identity. The proposed pathway for the biotransformation of thiram in surface water is that the substance transforms to CS2 directly and to CO2 through unstable degradates.

 

In the second key study (2014), the aerobic aquatic metabolism of the test substance was investigated in two different water/sediment systems (Abbey Lake and Swiss Lake) according to the OECD guideline 308 and GLP. The test was conducted in flow-through systems, in the dark at 20 ± 2 °C. The water/sediment systems were sampled in duplicates at day 0 and also after 0.04, 0.08, 0.21, 1, 6, 13, 39 and 60 days of incubation. Samples were analysed by LS and by HPLC. In order to confirm the identity of the test substance and metabolites, representative extracts were analysed using LC/MS and HPLC methods. The total recovery for both systems was > 90% at all sampling intervals. DMCS was the major metabolite identified for both systems in the water phase, accounting for a maximum of 36.1 % and 58.8 % of AR for Abbey Lake and Swiss Lake, respectively. Mineralisation of the substance (CO2 and CS2) reached 24.42 and 37.67% of AR by the end of the incubation (60 d) in Abbey Lake and Swiss Lake, respectively. Sediment-bound residues (non-extractables) for Abbey Lake increased throughout the study, reaching a mean maximum of 61.9 % at day 39 and declined by day 60, whereas non-extractables for Swiss Lake increased permanently reaching a mean maximum of 45.2 % at day 60. The study shows that thiram degrades rapidly to the major metabolite DMCS, converts partly to bound residues, and ultimately mineralises to carbon dioxide. The DT50 values were calculated in a new kinetic assessment in compliance with FOCUS kinetic (2006). The study resulted into the best fit DT50 values based on test material analysis of 0.14 d at 20°C (FOMC kinetics, recalculated to 0.3 d for 12°C) and 0.129 d at °C (SFO kinetics, recalculated to 0.27 d for 12°C) for Abbey Lake and Swiss Lake, respectively. Based on the quality of results and methodology this study was chosen as key.

 

In a further study (1995), the degradation and metabolism of tetramethylthiuram disulfide (CAS No. 137-26-8) in a natural water/sediment system (river Rhine) was investigated according to the German BBA Guidelines, Part IV, Section 5-1 and GLP conditions. Based on experience from previous studies a lower application rate of 16.26 µg/L was chosen. This study focused on the fate of the very polar radioactive fractions (MW1 to 9) detected by HPLC within the first several minutes of the HPLC-run and therefore the duration of the study was only 10 d. The radiolabeled test compound was incubated under aerobic conditions in 530 mL water and 300 g sediment (wet) at 20 °C for 10 days in the dark. The mean recovery of the radioactivity was 94.9±2.9%. Thiram degraded fast to 0.5% on Day 10 resulting in a DT50 of 0.7 d (1.5 days, recalculated to 12 °C). Concerning transformation products, polar fractions, i.e. MW1 to 9 were detected but could not be characterized. With the exception of MW2, all other fractions reached their maximum value (8% of the radioactivity applied) before or at day 2 of incubation and decreased until day 10 or were not any more detectable. MW2 was the only fraction, which increased until day 10. DMDTC-ME and the unknown radioactive fraction U were of minor importance, i.e. < 1.2% applied. Within the first days thiram may be hydrolysed to a small extent to CS2, but mineralization started very soon to achieve ca. 25% within 10 days of incubation.

 

In a further study (1992), the biodegradation of the substance in water/sediment systems (from a pond and a river) and aerobic conditions was investigated. The study resulted into half-lives ranging from 0.14 to 1.9 days (0.30 - 4.03 days, recalculated to 12 °C). The recoveries of the test item were between 87.8 – 90.7% AR after 101 d. 14C-thiram was degraded mainly to 14CO2 and 14CS2, which reached 65.8% and 60.8% of the applied RA for river and pond systems, respectively, over the incubation period of 101 days. However, the oxygen concentrations were in several cases very low (1.9 – 4.7 mg/L) and the aerobic conditions were not always met during the study. Therefore, the results of this study should be treated with caution and the study was used only as supporting information in spite of the longer duration.

 

The aerobic/anaerobic and anaerobic degradation of tetramethylthiuram disulfide in water/sediment was investigated in one more simulation study, resulting in degradation half-life of 4.25 days (9.02 days, recalculated to 12 °C). The main metabolite was CS2, which appeared very fast mainly within the first 14 days and then reached 77.5 % applied radioactivity after 252 days. Another important degradation product was CO2, which appeared after day 7 and reached 15.8 % at day 252. Three other non-identified metabolites (M6, M8 and M9) were of minor importance.

 

Results from water and sediment studies show mineralization of the substance in the environment. Anaerobic conditions might favour mineralization of the substance, as shown by the respective study.