polymeric zinc propylenebis(dithiocarbamate);propineb (ISO)

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: sediment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011/11/03 to 2014/06/25

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4300 (Aerobic Aquatic Metabolism)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.4400 (Anaerobic Aquatic Metabolism)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Remarks:

Specific Radioactivity: 3.40 MBq (91.80 µCi) / mg

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment

Remarks:

1) Anglersee, Leverkusen, Germany. This is a small reclaimed gravel-pit used for fishing. 2) Wiehltalsperre, lake close to Wiehl near Gummersbach, Germany, This a freshwater dam, water and sediment were collected from the forebay Nespen.

Details on source and properties of surface water:

Water and sediment were taken in 1 to 2 m distance to the lakefronts and filled separately in plastic containers (30 L). Sediment was obtained from the upper sediment layer (5 – 10 cm thickness). One day after sampling, the sediments were sieved to 2 mm and the waters were passed through a 0.063 mm mesh.

Aliquots of the water/sediment systems were characterized by the principal investigator with respect to the total organic carbon of the water and the sediment at start of equilibration as well as start and end of the study. In addition, aliquots of both sediments were characterized with respect to textural class, pH and cation exchange capacity. In addition, subsamples of both sediments were characterized in two separate GLP studies [10] with respect to texture, pH, cation exchange capacity and organic carbon content.

Details on source and properties of sediment:

The sediment moisture [g H2O ad 100 g sediment dry weight] was determined using a drying oven by drying of subsamples of the wet sediments at 105 °C

Duration of test (contact time):

100 d

Initial conc.:

1.2 other: mg/mL

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test systems were incubated in a temperature-controlled walk-in climatic chamber
Temperature: Main Test: 20.0 ± 0.1°C
Additional Test: 20.0 ± 0.1°C
Oxygen conditions: aerobic (trap attachments permeable for oxygen)
Light conditions: dark
Static / in motion supernatant water in smooth motion

Ten sampling intervals were distributed over the entire incubation period of 100 days, respectively. Duplicate samples were processed and analyzed 0, 0.167, 1 , 3, 8, 15, 30, 58, 78, 100 days after application. The DAT-0 samples were processed approximately 1 hour after application.

One day after sampling, the collected sediments were sieved to = 2 mm, the waters were passed through a 0.063 mm mesh. Static test flasks, laboratory microcosm flasks, for degradation in aquatic systems under aerobic conditions were used. These are special cylindrical glass containers (volume approx. 1000 mL, inner diameter approx. 10.5 cm, surface area approx. 86.6 cm2), and each container is fitted with a trap attachment (permeable for oxygen) containing soda lime for absorption of carbon dioxide and a polyurethane (PU) foam plug for adsorption of volatile organic compounds (VOC).

For preparation of the test systems, wet sediment with a weight equivalent to a volume of 175 mL was weighed into each vessel and 520 mL of the corresponding water were added. The water-to-sediment volume ratio used was approximately 3/1 with a water layer of approximately 6 cm and a sediment layer of approximately 2 cm. The flasks were then fitted with trap attachments, stoppers and stirrers.

The untreated test systems were equilibrated to study conditions by placement in a temperature-controlled walk-in climatic chamber at 20°C in the dark for 11 days prior to application. The equilibration was proven by repeated measurement of the oxygen saturation of the water, the pH of the water and the sediment as well as the redox potential of the water and the sediment in representative test systems. All those data were filed in the raw data but were not reported. For the purpose of isolation and identification of formed metabolites some further flasks (ID MID) were prepared. Later, for the purpose of isolation and identification of formed metabolites each 5 new test flasks (ID MID) were prepared on 2012-03-14. They were filled with 343.4 and 210.2 g of wet sediment from systems Anglersee and Wiehltalsperre, respectively, and 520 mL of the corresponding water.

The test item was suspended in water and the gently stirred suspension was directly used as application solution. On 2011-11-14, the day of application an amount of 12.12 mg Propineb was freshly suspended in 10 mL pure water, resulting in an application solution with a nominal concentration of 1.2 mg/mL (0.9 MBq/mL), labeled as WU55Appl. The resulting suspension was continuously mixed/stirred on the Vortex Genie2 equipment until the end of application. An aliquot of 156 µL application solution WU55Appl was applied dropwise onto the water surface of the respective equilibrated test systems in order to obtain a nominal concentration of 188 µg/test system. The application was performed under continuous stirring of the application solution.

After application, each test vessel (except the DAT-0 samples) was sealed with the special trap attachment and placed into a temperature-controlled walk-in climatic chamber for incubation at 20°C in the dark. The amount of applied test item and the homogeneity of the application were determined by transferring each 156 µL of the application solution WU55Appl into graduated cylinders before, during and after the application. Since some variation of measured values was obvious (as it is not surprising in case that such suspension of a polymer is applied) the conclusion was drawn to better set the value of 100% applied radioactivity (100% of AR) for the current study by taking the mean value of the total recovery of radioactivity from the processing of the respective DAT-0 samples: In case of test system Anglersee (A) the 100% AR was determined with 156.099 kBq, corresponding to 208.1 µg/batch.

In case of test system Wiehltalsperre (W) the 100% AR was determined with 148.792 kBq, corresponding to 198.4 µg/batch. Thus, for both test systems the nominal dose of 188 µg/batch was slightly exceeded. During incubation for up to 100 days at 20 ± 0.1 °C in the dark the supernatant water was in smooth motion, but the sediment remained undisturbed.

For the additional test Propineb was dissolved in 10 mL methanol, resulting in a stock solution with a nominal concentration of 0.5 mg/mL (1.7 MBq/mL) labeled as JR64-SS1. The radioactivity content was determined by liquid scintillation counting (LSC) as 1.6 MBq/mL (equal to 0.47 mg/mL). The stock solution stored at < -18 °C in the dark. This solution was used as application solution for the additional test. 212 µL of application solution JR64-SS1 were pipetted to the water surface of the test systems. Afterwards, the samples were incubated under continuous shaking (70 U/min) in a climatic chamber at 20 °C. One sample was prepared for each water/sediment system. No attempts were made to trap volatiles, and to analyze the sediments.

Parent/product:

parent

Compartment:

water

Key result

% Degr.:

100

Parameter:

not specified

Remarks:

Wiehltalsperre system

Sampling time:

100 d

Remarks on result:

other: estimated by analysis of degradation products

Parent/product:

parent

Compartment:

water

Key result

% Degr.:

100

Parameter:

not specified

Remarks:

Anglersee

Sampling time:

100 d

Remarks on result:

other: estimated by analysis of degradation products

Key result

Compartment:

natural water / sediment

DT50:

1 d

Type:

not specified

Temp.:

20 °C

Remarks on result:

other: estimated by analysis of degradation products

Transformation products:

yes

No.:

#4

No.:

#3

No.:

#2

No.:

#1

Details on transformation products:

• Formation of propineb-DIDT directly from [propane-1-14C]propineb
• Formation of 4-MI directly from [propane-1-14C]propineb via polar transient products or from propineb-DIDT.
• Formation of PTU from [propane-1-14C]propineb via unpolar transient products like Propineb-DIDT, ROI3 and ROI8. Obviously, the more acidic conditions in the supernatant water of Wiehltalsperre accelerate their degradation to PTU.
• Formation of PU from PTU
• Mineralization (carbon dioxide formation)
• Formation of non-extractable residues (NER).

Volatile metabolites:

no

Remarks:

Formation of volatile organic compounds (VOC) was insignificant as demonstrated by values of 0.1% AR at all sampling intervals in both water/sediment systems. Therefore, no identification of VOC was performed.

Residues:

yes

Remarks:

NER increased from 19.2% of AR at DAT-0 to 49.5% of AR at DAT-3, then declined to 35.2% of AR at DAT-100 in Anglersee. In Wiehltalsperre, NER increased from 27.3% of AR at DAT-0 to 67.5% of AR at DAT-15, and then slowly declined to 61.1% of AR at DAT-100

Details on results:

The maximum mean amount of carbon dioxide was 37.2 and 13.6% of AR at study end (DAT-100) for Anglersee and Wiehltalsperre systems, respectively. Formation of volatile organic compounds was insignificant as demonstrated by values of 0.1% of AR at all
sampling intervals for both water/sediment systems.

The mean radioactivity dosed to the water phase decreased from DAT-0 to DAT-100 from 66.0 to 19.6% of AR in Anglersee systems and from 62.0 to 14.2% of AR in Wiehltalsperre systems.

Degradation of propineb was accompanied by the formation of four degradation products in water, and following maximum amounts were observed: Propineb-DIDT with a maximum of 31.7% of AR at DAT-0.167 (system Anglersee), PU with a maximum of 42.3% of AR at DAT-3 (system Anglersee), PTU with a maximum of 24.0% of AR at DAT-0.167 (system Anglersee) and 4-MI with a maximum of 17.1% of AR at DAT-0 (system Anglersee).

In general, extractable residues in sediment were on a comparable low level during the study, from 14.8 to 5.9% of AR in system Anglersee, and between 9.1 and 13.9% of AR in system Wiehltalsperre. Therein, three degradation products with following maximum amounts were observed: Propineb-DIDT with a maximum of 4.1% of AR at DAT-0 and DAT-0.167 (system Anglersee), PU with a maximum of 11.4% of AR at DAT-78 (system Wiehltalsperre) and PTU with a maximum of 3.5% of AR at DAT-0 (system Anglersee).

Table two

Results synopsis on material balance and distribution of applied ¹⁴C

Water/Sediment System	Anglersee	Wiehltalsperre
Material Balance [% AR] *	94.9 – 104.8 (mean: 100.1)	100.0 – 104.9 (mean: 102.3)
Water Phase [% AR]	15.8 (DAT-78) – 69.1 (DAT-0.167)	14.2 (DAT-100) – 73.7 (DAT-0.167)
Sediment Extract [% AR]	5.3 (DAT-78) – 14.8 (DAT-0)	9.1 (DAT-0.167) – 13.9 (DAT-15)
Mean Max. ^14CO2 [% AR]	37.2	13.6
Mean NER [% AR]	19.2 (DAT-0) – 49.5 (DAT-3) 35.2 at DAT-100	21.5 (DAT-0.167) – 67.5 (DAT-15) 61.1 at DAT-100

*: minimum values not at the last samplings;   NER = non extractable sediment residues

 

Table three

Results synopsis on metabolism of Propineb in water/sediment systems

Identified major degradation products (mean maximum occurrence)
CO2 (37.2% AR)
Propineb-DIDT (35.8% AR)	PU (50.4% AR)
PTU (26.6% AR)	4-MI (17.1% AR)

Conclusions:

Propineb and its degradation products will be rapidly degraded in water/sediment
systems under aerobic conditions.
Formation of significant amounts of non-extractable residues and carbon dioxide
indicates a participation in the natural carbon cycle and the potential for a complete
mineralization of propineb. Therefore, propineb and its degradation products are not
expected to have a potential for accumulation in the environment

Executive summary:

The degradation of propineb was studied in two types of water/sediment systems under aerobic conditions in the dark at 20 ± 0.1 °C for a maximum duration of 100 days. 

 

The study followed the OECD Guideline for the Testing of Chemicals No. 308 with additional EU requirements (Regulation (EC) No 1107/2009 and Commision Directive 95/36/EC amending Council Directive 91/414/EC) and the US EPA OCSPP Fate, Transport and Transformation Test Guideline No. 835.4300 / 835.4400. The study was conducted in compliance with the OECD Principles of Good Laboratory Practice and the Principles of Good Laboratory Practice – German Chemical Law (ChemG).

 

The 100% of AR was determined with 156.099 kBq (corresponding to 208.1 μg/batch) for system Anglersee (A) and with 148.792 kBq (corresponding to 198.4 μg/batch) for system Wiehltalsperre (W). Duplicate samples were processed and analyzed 0, 0.167, 1, 3, 8, 15, 30, 58, 78, 100 days after application. The DAT-0 samples were processed approximately 1 hour after application.

 

The amounts of propineb and its degradation products in water and sediment extracts were determined by liquid scintillation counting (LSC) and by HPLC/radiodetection analysis. Degradation products were identified by HPLC-MS(/MS) including accurate mass determination and/or by co- chromatography with reference items. The mean material balance was 100.1% of AR for system Anglersee, and 102.3% of AR for system Wiehltalsperre.

 

The maximum mean amount of carbon dioxide was 37.2 and 13.6% of AR at study end (DAT-100) for Anglersee and Wiehltalsperre systems, respectively. Formation of volatile organic compounds was insignificant as demonstrated by values of < 0.1% of AR at all sampling intervals for both water/sediment systems. The mean radioactivity dosed to the water phase decreased from DAT-0 to DAT-100 from 66.0 to 19.6% of AR in Anglersee systems and from 62.0 to 14.2% of AR in Wiehltalsperre systems. 

 

Extractable residues in the total system (water and sediment extracts) decreased in system Anglersee from 80.8 at DAT-0 to 21.2% of AR at DAT-78, and then slightly increased to 25.5% of AR at DAT-100. In system Wiehltalsperre, extractable residues in the total system decreased from DAT-0 to DAT-100 from 72.7 to 26.7% of AR.

 

NER increased from 19.2% of AR at DAT-0 to 49.5% of AR at DAT-3, and then declined to 35.2% of AR at DAT-100 in Anglersee systems. In Wiehltalsperre systems, NER increased from 27.3% of AR at DAT-0 to 67.5% of AR at DAT-15, and then slowly declined to 61.1% of AR at DAT-100. Propineb residues dissipated from the water rapidly due to degradation as well as by translocation of residues into the sediment (mainly forming NER therein).

 

Degradation of propineb in the total system was accompanied by the formation of four degradation products following maximum amounts observed: Propineb-DIDT with 35.8% of AR at DAT-0.167 (system Anglersee), PU with 50.4% of AR at DAT-3 (system Anglersee), PTU with 26.6% of AR at DAT-0.167 (system Anglersee) and 4-MI with 7.1% of AR at DAT-0 (system Anglersee). 

 

Altogether, available propineb DT50 data indicate that it is degrading quite fast, dependent on temperature, pH and concentration of suspension (for the latter, the lower the faster). 

 

The calculated half-live for the dissipation of the major metabolite (propineb- DIDT) from the water was 1.4 and 0.004 days for system Anglersee and Wiehltalsperre, respectively. 

 

It is concluded that propineb and its degradation products will be rapidly degraded in the aquatic environment. Formation of significant amounts of non-extractable residues and carbon dioxide indicates a participation in the natural carbon cycle and the potential for a complete mineralization of propineb. Therefore, propineb and its degradation products are not expected to have a potential for accumulation in the environment.

Description of key information

The degradation of propineb was studied in two types of water/sediment systems under aerobic conditions in the dark at 20 ± 0.1 °C for a maximum duration of 100 days. 

The study followed the OECD Guideline for the Testing of Chemicals No. 308 with additional EU requirements (Regulation (EC) No 1107/2009 and Commision Directive 95/36/EC amending Council Directive 91/414/EC) and the US EPA OCSPP Fate, Transport and Transformation Test Guideline No. 835.4300 / 835.4400.

For modelling purposes a worst case total system DT₅₀ of 1.0 day at 20^oC (2.12 d at 12^oC) is proposed based on the LSC estimation of degradates.

It is concluded that propineb and its degradation products will be rapidly degraded in the aquatic environment.

Key value for chemical safety assessment

Half-life in freshwater sediment:

1 d

at the temperature of:

20 °C

Whole System

Half-life in whole system:

2.12 d

at the temperature of:

12 °C

Type of system:

fresh water and sediment