Teflubenzuron

Biodegradation in soil

Description of key information

The DT50 of teflubenzuron in soil was determined to be 181.4 days at 10 °C. The DT50 of teflubenzuron was calculated to be 154.6 days at 12 °C (Chapter R.7b, p.222: Endpoint specific guidance Version 4.0 – June 2017).

Key value for chemical safety assessment

Half-life in soil:

154.6 d

at the temperature of:

12 °C

Additional information

Four studies on aerobic degradation in soil (laboratory) were performed with teflubenzuron. Three of them were submitted in the EU in accordance with Regulation (EU) No 1107/2009 concerning the placing of plant protection products on the market and considered as relevant by the Rapporteur Member State (UK). For two of the three studies the test material was labelled in the aniline ring of the molecule, one in the benzoyl ring. The fourth study is not considered valid due to poor quality and was not included in the dossier submitted under Regulation (EU) No 1107/2009.

For details please refer to Draft Assessment Report for teflubenzuron prepared according to the Commission Regulation (EU) No 1107/2009, Volume 3 – B.8 (AS) (October 2007) and the final addendum to DAR (August 2008).

However, the three valid studies on aerobic degradation in soil are available and discussed in a weight of evidence approach. In addition, data concerning the degradation of metabolites of teflubenzuron is summarized. Degradation under anaerobic conditions were investigated in two of the studies but were considered not to be expected under the proposed GAP.

 

Batelle (2003c): Aerobic Rate of Soil Degradation of BAS 309 I (Teflubenzuron). Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: 2003/1010910; crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.2.1/01

 

The degradation rate of teflubenzuron (BAS 309 I) was investigated under aerobic conditions in three German soils (Speyer 2.1, Speyer 3A and Speyer 5M). The soils were treated with [¹⁴C]-teflubenzuron labelled in the aniline ring of the molecule at a rate of 0.01536mg/100g soil (dry weight basis), equivalent to a maximum field application rate of 225g a.s./ha. Soil aliquots were incubated in the laboratory in the dark under aerobic conditions with a soil moisture of 40% of the maximum water holding capacity (MWHC) and a temperature of 20°C ± 2°C, additionally one soil was incubated at 10°C. An incubation system with continuous aeration was used with an attached trapping system for the determination of volatile compounds. The microbial biomass was determined according to “ISO 14240-2 Soil Quality - Determination of soil microbial biomass - Part 2: Fumigation-extraction method”, before the start of the study and at day 100. Duplicate soil samples were taken 0, 7, 14, 28, 42, 63 and 100 days after treatment (DAT). The soil samples were extracted with a mixture of 150 mL acetonitrile/water 7:3 during 2 hours on an orbital shaker at ambient temperature. The samples were filtered and the centrifuge tubes rinsed with 2 x 50 mL acetonitrile and 50 mL ether. The combined extracts were transferred into a separation Tunnel. A volume of 150 mL MilliQ water and 150 mL dichloromethane were added and the mixture agitated by hand for several minutes. Following solvent extraction, the organic phase was collected. The aqueous phase was re-extracted twice more with 150 mL dichloromethane while combining the organic phases. Aliquots of the organic and aqueous phase were taken and analyzed via LSC to identify the total amount of radioactive residue. Following the extraction procedure, combustion analysis on post-extraction solids was performed using triplicate aliquots of each representative soil sample.

Additionally, the amount of formed volatiles was determined for each sampling point except on day 0 and analyzed by LSC. A full mass balance was provided for each sampling interval.  As a result, teflubenzuron degraded in aerobic soils with DT₅₀ values of 140.3, 72.8 and 120.9 days in the soils Speyer 2,1, Speyer 3A and Speyer 5M, respectively and with a DT₅₀ value of 181.4 days at 10 °C. At the same time the fraction of non-extractable residues increased reaching between 33.05 (at day 100 in Speyer 2.1) and 51.6 % (at day 63 in Speyer 3A). The levels of ¹⁴CO₂ did not exceed 0.9% AR at any point in the study. No other volatiles were detected.

Teflubenzuron forms bound residues through the chloroaniline moiety of its degradation products 3,5-dichloro-2,4-difluorophenylurea and 3,5-dichloro-2,4-difluoroaniline under aerobic conditions. 3,5-dichloro-2,4-difluorophenylurea (CL 902374) occurred at a maximum of 10.71% AR in soil #2 (Speyer 3A) 14 days after application, with calculated DT₅₀ values of 5.2 to 10.9 days.

3,5-dichloro-2,4-difluoroaniline (CL 902373) occurred at a maximum of 5.58% AR in soil #3 (Speyer 5M) 42 days after application, with calculated DT₅₀ values of 3.7 to 9.5 days.

 

Supporting information

The following two studies were considered as supporting information.

 

SRC (1990): Teflubenzuron [14C-benzoyl ring] Degradation in soil under aerobic and anerobic conditions. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: TZ-620-012; SBGR.90.117.crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.1.1/01

 

The fate and behaviour of ¹⁴C-teflubenzuron was studied in a silty clay loam soil under aerobic and anaerobic conditions after flooding.

Teflubenzuron degradation proceeded at a moderately rapid rate under aerobic conditions with a DT₅₀ of 29 days and DT₉₀ of 108 days. Following flooding the soil with water and with nitrogen to create anaerobic conditions, the rate of ¹⁴CO₂ evolution slowed considerably. However the overall rate of degradation (i.e. loss of teflubenzuton) did not change indicating that the initial steps in the degradation route were not affected by the change in conditions.

The major extractable radioactive component at all sampling times under aerobic and anaerobic conditions was teflubenzuron, but at least 7 other components were observed in extracts of Day 60 anaerobic soil accounting for a total of less than 5% of the applied radioactivity.

The radioactive product expected from the initial cleavage of the [¹⁴C-benzoyl]-teflubenzuron was 2,6-difluorobenzoic acid. It was, however, not observed under aerobic conditions, which indicated that its rate of depletion exceeded its rate of formation, but trace amounts were identified in the anaerobic soil where the rate of degradation of the benzoyl ring was slower.

Another minor degradation product identified under anaerobic conditions was formed by replacement of fluorine by hydroxyl in the 4-position of the aniline ring. This may be an aerobic transformation that was detected because of the slower rate of subsequent catabolism under anaerobic conditions. Alternatively reductive defluorination is a possible first step, followed by replacement of hydrogen by hydroxyl. Decarboxylation of 2,6-difluorobenzoic acid would also be expected. This provides good evidence for the mineralization of the bound residues under aerobic conditions.

The ultimate degradation product was carbon dioxide, which accounted for 20-50% AR from day 30.

Residues in unextracted soil were not determined, only quantified as captured 14CO2 after soil burning.

 

Celamerck (1985): Aerobic and Anaerobic Degradation of CME 134 in a Sandy Loam Soil. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: TZ-620-004; 134AA-921-004 (Shell Agrar); crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.1.1/02

 

The degradation of ¹⁴C-CME was investigated in a sandy loam soil (5 mg/kg) under aerobic and anaerobic conditions. Under aerobic conditions, half of the originally applied amount was degraded after 12-13 weeks (80-90 days). In the anaerobic test, ¹⁴C-CME 134 was broken down more rapidly, as only half of the parent compound applied could be recovered in the soil 2 weeks after the application.

In both tests, 3,5-dichloro-2,4-difluoroaniline and 3,5-dichloro-2,4-difluorophenyl-urea could be identified as metabolites. The aniline amounted to maximum values of 5.4% and 1.0% of the applied radioactivity in the aerobic and anaerobic test, respectively. The corresponding values of the urea compound were 10.4% under aerobic and 28.2% under anaerobic conditions. The metabolites were degraded further in both tests. Additionally, a number of unknown trace compounds could be extracted (at least 8 in both tests) none of which exceeded 2% AR (0.1 mg/kg). All together, they reached maximum values of 13.4% AR in the aerobic and 11.9% AR in the anaerobic study.

Considerable proportions of radioactivity were firmly bound to soil constituents under both conditions. In aerobic conditions, teflubenzuron degraded to bound residues (33.3% AR on day 343) and ¹⁴CO₂ (6.5% AR on day 343). In anaerobic conditions, teflubenzuron degraded to bound residues (34.5% AR after 59 days).

Further radioactivity could be solubilized by treatment of the bound residues with sodium hydroxide solution or ethanolamine. In both tests 3,5-dichloro-2,4-difluoroaniline was found among the solubilized radioactive products indicating that the bound residues were formed at least partly by the aniline or compounds still containing the aniline moiety. Under aerobic conditions, 6.5% AR were released as volatile compounds till the end of the study (343 days). This proportion of radioactivity was identified ¹⁴CO₂.

 

Normalization of laboratory degradation endpoints to reference conditions

Since for environmental fate modeling soil DegT₅₀ values at reference conditions (temperature of 20°C and soil moisture at field capacity, i.e. pF2) are required, the modeling endpoints (DegT₅₀) reported in Batelle (2003a) and Celamerck (1985) were normalized following the recommendations of FOCUS [FOCUS (2012): Generic Guidance for Tier 1 FOCUS Ground Water Assessments, version 2.2 (May. 2014), 66 pp.]. Since the laboratory study Batelle (2003a) was performed at 20°C, a temperature correction was not necessary. The soil moisture normalization was performed using the moisture dependency equations by Walker. For the study Celamerck (1985), both temperature and moisture correction was necessary.

Table: Normalization of teflubenzuron DegT50 values (laboratory) to reference conditions
Study DocID	Soil	Kinetic model	Study temp. [°C]	Study moisture [%]	FOCUS pF2 moisture [%]	DegT50,act [d]	DegT50,ref[d]
BASF Doc. ID 2003/1010910	Speyer 2.1 (sand)	SFO	20	12	12.0	140.3	140.3
	Speyer 3A (loamy sand)	SFO	20	20	25.0	72.8	62.2
	Speyer 5M (loamy sand)	SFO	20	17.2	19.0	120.9	112.8
BASF Doc. ID TZ-620-004	Sandy loam (Schlüter)	FOMC ^1)	22	11.175	14.9 at 0.33bar (actual value for soil)	77.0 ^1)	73.2
Geomean (days (normalized))							92.1
^1) Although this value is actually an FOMC DT50 the RMS considers the inclusion of this value in the calculation of the geomean is the most appropriate way of handling this data point. The FOMC DT90 values were not supported by any of the other laboratory or field results and are likely to be an artefact of the laboratory study conditions. DegT50,act = DT50 at study conditions [d] DegT50,ref = DT50 at reference conditions [d]

 

Additional information – field studies

These studies are summarized in the following for sake of completeness but have however not been documented in separate IUCLID Endpoint Study Records.

Batelle (2003d): Dissipation of BAS 309 I (Teflubenzuron) following the application of NOMOLT 150 SC in a field trial in Germany. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: 2003/1010901; crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.2.2/01

Batelle (2003e): Dissipation of BAS 309 I (Teflubenzuron) following the application of NOMOLT 150 SC in a field trial in the Netherlands. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: 2003/1011770; crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.2.2/02

Batelle (2003f): Dissipation of BAS 309 I (Teflubenzuron) following the application of NOMOLT 150 SC in a field trial in Italy. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: 2003/1011775; crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.2.2/03

Batelle (2003g): Dissipation of BAS 309 I (Teflubenzuron) following the application of NOMOLT 150 SC in a field trial in Southern France. Doc ID according to Draft Assessment Report prepared in compliance with Regulation (EC) No 1107/2009: 2003/1011774; crossreference to Draft Assessment Report according to Regulation (EU) No 1107/2009: CA 7.1.1.2.2/04

 

Two field studies were performed in Northern Europe (Germany and Netherlands) and two field studies in Southern Europe (Italy and Southern France) to investigate the degradation and dissipation of teflubenzuron in typical apple growing regions. The product was applied broadcast to bare soils in the autumn, at a rate of 2.4 l/ha (0.360 kg a.s./ha nominal, 0.346 kg a.s./ha actual). This worst case amount corresponds to the total of the 3 annual applications on apples at 0.12 kg a.s./ha applied in 1 spray, instead of at intervals of 14 days.

Soil samples were taken over a period of 8 months at depths of 0 – 30 cm and 30 – 60 cm. Sampling times were 1 or 2 hours before application, then 3 hours, 2 weeks, 1, 2, 3, 4, 6, and 8 months after application. All the samples were immediately frozen at < - 18 °C, packed and shipped frozen to the laboratory where they were kept at < - 18 °C until analyses were performed.

In the laboratory the cores were broken into 10 cm segments, which were analyzed for teflubenzuron using HPLC with UV detection. The LOQ was 0.005 mg/kg.

In laboratory studies, the metabolite 3,5-dichloro-2,4-difluorophenyl-urea (CL 902374) occurred at a maximum of 10.71% AR in 1 soil (Speyer 3A) 14 days after application, with calculated DT₅₀ of 5.2 to 10.9 days (3 soils) at temperatures of 10-20 °C. Because of the low levels of metabolite that might have appeared (less than 10% of parent), and its very short DT₅₀ (less than 10 days) in comparison to the sampling schedule, it was not deemed necessary to attempt to measure this metabolite during the course of this study.

DT₅₀ and DT₉₀ were calculated assuming Simple First Order kinetics.

Only time points T-0 to approximately T-90 were considered for correlation due to low residue levels.

Analyses of the first sampling 3 hours after application for all 4 trials, carried out 14 to 15 months after the sampling, showed that more than 79% (79.7 to 114.4%, average 90.9%) of theoretically applied quantities teflubenzuron were recovered. (Table 7.1.1.2.2/-2), demonstrating that teflubenzuron is stable in soil samples stored at -18⁰ C for at least 14 months.

 

Table: Summary of recovery values
Field dissipation study location	Date of first samp-ling	Dates of first and last analyses in the laboratory (after storage at –18 ^0C)	Theoretical quantity applied (1)   (kg a.s./kg soil)	Quantity recovered on Day 0 sample   (kg a.s./kg soil)	Recovered quantity of theoretically applied (%)
Germany	October 18, 2001	February 12-20, 2003	0.2304	0.2636	114.4
Netherlands	October 26, 2001	February 22, March 5, 2003	0.2304	0.1962	85.2
Italy	October 23, 2001	December 2, 2002 - January 3, 2003	0.2304	0.1939	84.2
Southern France	Novem-ber 7, 2001	February 3 - March 11, 2003	0.2304	0.1837	79.7

 

The average recoveries obtained from soil fortification experiments at 0.005 mg/kg (n = 12) and 0.05 mg/kg (n = 11) were in the range of 83.8 to 104.8%.

In Germany average monthly temperatures ranged from 0 °C to 19.0 °C and total rainfall amounted to 694 mm. In the Netherlands daily temperatures ranged from -10.9 °C to 35.1 °C and total rainfall amounted to 1007.7 mm. In Italy daily temperatures ranged from – 7.7 °C to 26.0 °C and total rainfall amounted to 910.2 mm. In France, daily temperatures ranged from – 7.9 °C to 35.2 °C and total rainfall amounted to 373.1 mm.

Following application of teflubenzuron in the autumn on bare soils, residue concentrations declined rapidly with time, and had almost disappeared after 1 apple growing season, leaving less than 0.02 mg/kg after 2 months, only 0.007 to 0.008 mg/kg after 6 months and between < 0.005 (LOQ) to 0.007 mg/kg after 8 months, with no significant difference between North and South. Except for 1 sample (Netherlands, 3 hours after application), no residues of teflubenzuron were found at or above the LOQ below the top 0-10 cm layer. No residues of teflubenzuron were found at or above the LOQ in any of the control samples analysed.

The indivual residue results are presented below.

Table: Field dissipation of teflubenzuron (SC 150 formulation) in Germany after application of 0.36 kg a.s./ha on bare soil (mg/kg).
Time point (hours)	Residues determined in soil layer			Total residues
	0 – 10 cm	10 – 20 cm	20 – 30 cm
- 2 hours	ND	N/A	N/A	ND
+ 3 hours	0.2636	ND	N/A	0.2636
13	0.1014	0.0047	N/A	0.1060
28	0.1184	N/A	N/A	0.1184
60	0.0130	N/A	N/A	0.0130
97	0.0050	N/A	N/A	0.0050
118	0.0051	N/A	N/A	0.0051
179	0.0078	N/A	N/A	0.0078
239	0.0042	N/A	N/A	0.0042
ND:  not determined N/A: not analysed

 

 

Table: Field dissipation of teflubenzuron (SC 150 formulation) in the Netherlands after application of 0.36 kg a.s./ha on bare soil (mg/kg).
Time point (hours)	Residues determined in soil layer			Total residues
	0 – 10 cm	10 – 20 cm	20 – 30 cm
- 1 hours	ND	N/A	N/A	ND
+ 3 hours	0.1880	0.0082	N/A	0.1962
14	0.0945	0.0043	N/A	0.0988
31	0.0452	N/A	N/A	0.0452
63	0.0258	N/A	N/A	0.0258
90	0.0118	N/A	N/A	0.0118
129	0.0051	N/A	N/A	0.0077
180	0.0077	N/A	N/A	0.0074
241	0.0056	N/A	N/A	0.0056
ND:  not determined N/A: not analysed

 

 

Table: Field dissipation of teflubenzuron (SC 150 formulation) in the Italy after application of 0.36 kg a.s./ha on bare soil (mg/kg).
Time point (hours)	Residues determined in soil layer			Total residues
	0 – 10 cm	10 – 20 cm	20 – 30 cm
- 1 hours	0.0075	ND	N/A	0.0075
+ 3 hours	0.1897	0.0042	N/A	0.1939
15	0.0519	ND	N/A	0.0519
31	0.0266	ND	N/A	0.0266
59	0.0116	ND	N/A	0.0116
91	0.0074	ND	N/A	0.0071
121	0.0104	ND	N/A	0.0104
180	0.0083	ND	N/A	0.0083
243	0.0074	ND	N/A	0.0074
ND:  not determined N/A: not analysed

 

 

Table: Field dissipation of teflubenzuron (SC 150 formulation) in the Italy after application of 0.36 kg a.s./ha on bare soil (mg/kg).
Time point (hours)	Residues determined in soil layer			Total residues
	0 – 10 cm	10 – 20 cm	20 – 30 cm
- 1 hours	0.0093	ND	N/A	0.0093
+ 3 hours	0.1837	ND	N/A	0.1837
14	0.0828	ND	N/A	0.0838
30	0.0445	N/A	N/A	0.0445
61	0.0102	N/A	N/A	0.0102
90	ND	N/A	N/A	ND
125	ND	N/A	N/A	ND
180	0.0081	N/A	N/A	0.0081
243	0.0060	N/A	N/A	0.0060
ND:  not determined N/A: not analysed

 

Assuming Simple First Order kinetics, application of 0.36 kg a.s./ha resulted in DT₅₀ values for teflubenzuron ranging from 16.6 to 23.5 days and DT₉₀ values from 55.0 to 78.0 days in the North, and 17.1 to 20.7 days and DT₉₀ values from 56.9 to 68.7 days in the South, respectively.

Table: Summary of field dissipation trials of teflubenzuron (SC 150 formulation) in Europe after application of 0.36 kg a.s./ha on bare soil
Location	Soil Type	DT 50 (days)	DT 90 (days)
Germany (Stuttgart)	Silty loam	16.6	55.0
Netherlands (Limburg)	Loess	23.5	78.0
Italy (Como )	Sandy loam	20.7	68.7
Southern France (Vaucluse)	Sandy silty loam	17.1	56.9

 

Conclusion

Laboratory studies

In one study the degradation of [14C]-teflubenzuron was investigated in three typical use soils, incubated at 20 °C under aerobic conditions for a period of up to 100 days. Additionally one soil (soil #3) was also incubated at 10 °C.

Under aerobic conditions teflubenzuron degrades moderately quickly at 20 °C (DT₅₀ values of 72.6 to 140.3 days and DT₉₀ values of 241.2 to 465.7 days), to slowly at 10 °C (DT₅₀ of 181.4 days and DT₉₀ of 601.6 days).

 

The DT50 of teflubenzuron was calculated to be 154.6 days at 12 °C using the EUSES formula (643):

DT50bio_{soil_temp env} = DT50bio_{soil_temp test *} e ^{(0.08*(TEMPtest-TEMPenv))}

Input
DT50biosoil_temp test	half-life for biodegradation in soil at a temperature of the data set	[d]
TEMPtest	temperature of the measured data in simulation test	[K]
TEMP	environmental temperature	[K]
Output
DT50biosoil_temp env	half-life for biodegradation in soil at the environmental temp.	[d]

 

3,5-dichloro-2,4-difluorophenylurea occurred at a maximum of 10.71% AR in soil #2 (Speyer 3A) 14 days after application, with calculated DT₅₀ values of 5.2 to 5.5 days at 20 °C and 10.9 days at 10 °C.

3,5-dichloro-2,4-difluoroaniline occurred at a maximum of 5.58% AR in soil #3 (Speyer 5M) 42 days after application, with calculated DT₅₀ values of 3.7 to 9.5 days at 20 °C and 5.9 days at 10 °C.

 

In a second study the DT₅₀ of teflubenzuron in a silty clay loam was 29 days and the DT₉₀ was108 days, following first order kinetics.

 

In a third study, the DT₅₀ of teflubenzuron in a sandy loam was 80-90 days under aerobic conditions and 14 days under anaerobic conditions, following first order kinetics. Recalculation of the aerobic data following first order kinetics gave a DT₅₀ for teflubenzuron of 77.0 days, and DT₅₀ values of 16.8 days and 21.7 days for metabolites 3,5-dichloro-2,4-difluorophenyl-urea and 3,5-dichloro-2,4-difluoroaniline, respectively.

Overall the route and rate of degradation studies showed that teflubenzuron degraded moderately quickly following first order kinetics under aerobic laboratory conditions at temperatures of 10 to 22 ⁰C with DT₅₀ values of 29 to 181 days and DT₉₀ values of 108 to 601 days. Under anaerobic conditions teflubenzuron degraded following first order kinetics with DT₅₀ of 14 days.

Field studies

Teflubenzuron was applied at 0.36 kg a.s./ha to 4 different bare soils, two in Northern Europe and two in Southern Europe. No residues were found at or above the LOQ (0.005 mg/kg) in the soil layer below 10 cm (except 1 sample 3 hours after application), indicating no potential for leaching. Teflubenzuron degraded rapidly. Less than 0.02 mg/kg was detected after 2 months, and between < 0.005 (LOQ) and 0.007 mg/kg after 8 months. Assuming first order kinetics, the DT₅₀ values ranged from 16.6 to 23.5 days and the DT₉₀ values from 55.0 to 78.0 days. Teflubenzuron was stable in soil samples stored for at least 14 months.