Desmedipham

Biodegradation in soil

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991-04-08 to 1991-12-04

Reliability:

1 (reliable without restriction)

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 307 (Aerobic and Anaerobic Transformation in Soil)

Version / remarks:

2002

Deviations:

yes

Remarks:

- LOD and LOQ of the analytical method is not given (the lowest measured AR was) - Soil sampling and storage of the soil is not described - Use history of desmedipham at the field site is not given - Microbial activity was not measured

Qualifier:

according to guideline

Guideline:

other: BBA Guidelines for the Official Testing of Plant Protection Products, Part IV.

Version / remarks:

1986

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

USDA (US Department of Agriculture)

Year:

1991

Soil no.:

#1

Soil type:

other: N/A

% Clay:

5.1

% Silt:

13

% Sand:

82

% Org. C:

2.29

pH:

6

CEC:

9.7 meq/100 g soil d.w.

% Moisture content:

47.51

Soil no.:

#2

Soil type:

sandy loam

% Clay:

14.9

% Silt:

11.8

% Sand:

73.3

% Org. C:

1.52

pH:

4.9

CEC:

10.19 meq/100 g soil d.w.

% Moisture content:

50.49

Soil no.:

#3

Soil type:

clay loam

% Clay:

32.2

% Silt:

28.8

% Sand:

38.9

% Org. C:

3.06

pH:

5.9

CEC:

13.29 meq/100 g soil d.w.

% Moisture content:

73.21

Soil no.:

#4

Soil type:

clay loam

% Clay:

24.8

% Silt:

29.5

% Sand:

45.6

% Org. C:

1.16

pH:

7

CEC:

12.12 meq/100 g soil d.w.

% Moisture content:

58.26

Details on soil characteristics:

Soil #1:Speyer 2.2, GE
Soil #2: Sandy loam, Scotland
Soil #3: Acidic clay loam, Scotland
Soil #4: Alkaline clay loam, Scotland

Soil No.:

#1

Duration:

100 d

Soil No.:

#2

Duration:

100 d

Soil No.:

#3

Duration:

100 d

Soil No.:

#4

Duration:

100 d

Soil No.:

#1

Initial conc.:

0.69 kg/ha d.w.

Based on:

act. ingr.

Soil No.:

#2

Initial conc.:

0.69 kg/ha d.w.

Based on:

act. ingr.

Soil No.:

#3

Initial conc.:

0.69 kg/ha d.w.

Based on:

act. ingr.

Soil No.:

#4

Initial conc.:

0.69 kg/ha d.w.

Based on:

act. ingr.

Parameter followed for biodegradation estimation:

radiochem. meas.

Soil No.:

#1

Temp.:

21°C

Humidity:

47.51 MWHC (%w/w)

Soil No.:

#2

Temp.:

21°C

Humidity:

50.49 MWHC (%w/w)

Soil No.:

#3

Temp.:

21°C

Humidity:

73.21 MWHC (%w/w)

Soil No.:

#4

Temp.:

21°C

Humidity:

58.26 MWHC (%w/w)

Details on experimental conditions:

EXPERIMENTAL DESIGN
- Soil preincubation conditions (duration, temperature if applicable): Flasks were incubated at 21 ± 2°C for the duration of the study.

- Details of traps for CO2 and organic volatile, if any: The gas mixture leaving the Speyer 2.2 was passed through a safety trap, ethanediol (ca 50 g) and ethanolamine (2 x ca 50 g) to trap any liberated non-specific organic volatiles and carbon dioxide, respectively. The gas mixtures leaving the Sandy Loam, Acidic Clay Loam and Alkaline Clay Loam were passed through combined safety traps, ethanediol (ca. 300 g) and ethanolamine (2 x ca 300 g) for each soil type. Traps were sampled and replenished at weekly intervals and at sampling. Aliquots of each trapping solution were submitted to LSC for quantifying the amount of radioactivity present.

Test material application
- Application method (e.g. applied on surface, homogeneous mixing etc.): Sufficient number of soil samples (12; ca 50 g oven dry basis) were weighed into Erlenmeyer flasks (250 ml capacity) to enable duplicate analysis 45.92 µg of [phenoxy -UL-14C] and [aniline -UL-14C] desmedipham was applied to the surface of each soil and the contents of the flasks gently agitated to increase the contact of the microbial biomass with the test material. Following dosing, the flasks were connected to a continuous air-flow system and a stream of moist carbon dioxide-free air drawn over the soil surface.

Soil No.:

#1

DT50:

28.2 d

Type:

other: Non-normalised best fit

Temp.:

21 °C

Soil No.:

#2

DT50:

25.1 d

Type:

other: Non-normalised best fit

Temp.:

21 °C

Soil No.:

#3

DT50:

33.1 d

Type:

other: Non-normalised best fit

Temp.:

21 °C

Soil No.:

#4

DT50:

8 d

Type:

other: Non-normalised best fit

Temp.:

21 °C

Transformation products:

not measured

Remarks:

Metabolites that were analysed were diphenyl urea and EHPC. Less than 2 % of AR was found as EHPC. An unidentified metabolite was found max 2.6 % of AR.

Residues:

yes

Details on results:

Radiolabelled CO2 was collected throughout the incubation period. After 100 days, a mean of 37.76% of the applied radioactivity was recovered as 14CO2 from the Speyer 2.2. Corresponding values for Sandy Loam, Acidic Clay Loam and Alkaline Clay Loam were 21.40%, 25.74% and 23.08% respectively. Organic volatile evolution for each soil was negligible (<0.3%). The mean bound residues for Speyer 2.2, Sandy Loam, Acidic Clay Loam and Alkaline Clay Loam at 100 days post dose were 55.84%, 67.22%, 57.26% and 67.24%, respectively.

Kinetic evaluation of the degradation in 4 tested soils ([phenoxy -UL-¹⁴C]desmedipham)

Speyer 2.2: The SFO fit for desmedipham in soil is deemed acceptable (Table 2). Therefore, for modelling purposes, a DT₅₀ of 28.2 d was derived for desmedipham.

Sandy loam: The SFO fit for desmedipham is deemed acceptable (Table 2). Therefore, for modelling purposes, a DT₅₀ of 25.1 d was derived for desmedipham.

Acidic clay loam: The SFO fit for desmedipham is deemed acceptable (Table 2). Therefore, for modelling purposes, a DT₅₀ of 33.1 d was derived for desmedipham.

Alkaline clay loam: The SFO fit for desmedipham is deemed marginal (Table 2). The initial value was fixed to 100%, but this gave no improvement in the outcome. Therefore, an FOMC fit was done, which was an improvement, although the tail of the fit still undershoots the two final data points. Therefore, for modelling purposes, a conservative estimate of DT₅₀ was derived from the FOMC DT₉₀, giving a DT₅₀ for desmedipham of 9.7 d (DT₉₀: 32.3 / 3.32).

 

Table 2: Summary of the kinetic evaluation of the degradation in soil Schering 161 

	kinetic model	M0	ff	parameter	DT50 [days]	DT90 [days]	2 [%]	t test probability
P-DMP ^1	SFO	86.7		k = 0.0246	28.2	93.5	6.4	k: <0.001
P-DMP ^2	SFO	87.6		k = 0.0276	25.1	83.5	6.2	k: <0.001
P-DMP ^3	SFO	81.6		k = 0.0209	33.1	110.0	5.9	k: <0.001
P-DMP ^4	SFO	87.3		k = 0.0829	8.4	27.8	7.5	k: <0.001
P-DMP ^4	SFOinitial fixed	100		k = 0.1070	6.5	21.5	13.0	k: <0.001
P-DMP ^4	FOMC	88.2		α = 4.446 β = 47.596	8.0	32.3	7.8	n.a.
Study conclusion (Chapple 2014):                                                           n.a. = not applicable for FOMC model   P-PMP ^1 SFO: fit visually and statistically acceptable (X^2 = 6.4%) (comment RMS: agreed) P-PMP ^2 SFO: fit visually acceptable, but not statistically acceptable (X^2 = 6.2%) (RMS comment: agreed) P-PMP ^3 SFO: fit visually and statistically acceptable (X^2 = 5.9 %) (RMS comment: agreed) P-PMP ^4 SFO: fit visually not acceptable, but statistically acceptable (X^2 = 7.5 %) (RMS comment: some overestimation of degradation at the tail of the fit) P-PMP ^4 SFOinitial fixed: fit visually not acceptable, but statistically acceptable (X^2 = 13.0 %) (RMS comment: some overestimation of degradation at the tail of the fit) P-PMP ^4 FOMC: fit visually and statistically acceptable (X^2 = 7.8 %) (RMS comment: agreed)   Trigger endpoint / modelling endpoint for P-DMP^1: SFO DT50: 28.2 days Trigger endpoint / modelling endpoint for P-DMP^2: SFO DT50: 25.1 days Trigger endpoint / modelling endpoint for P-DMP^3: SFO DT50: 33.1 days Trigger endpoint for P-DMP^4: FOMC DT50: 8.0 days Modelling endpoint for P-DMP^4: Pseudo SFO: DT90/3.32= 9.7 days

¹ Speyer 2.2, ² Sandy Loam, ³ Acidic Clay Loam, ⁴ Alkaline Clay Loam

Conclusions:

RMS comments and conclusion: The study was partly performed in line with the OECD test guideline 307 (2002). The following deviations were noted:
LOD and LOQ of the analytical method is not given (the lowest measured AR was Soil sampling and storage of the soil is not described
Use history of desmedipham at the field site is not given Microbial activity was not measured
The total radioactive recovery was close to 100 % which fulfils the quality criteria in OECD TG. Also, the pH
and orgC were within the recommended limits of the OECD TG. RMS considers the study valid. The kinetic evaluation followed the FOCUS DegKinetics Report (2006) as described in the beginning of this Section. The non-normalised best fit DT50 values of 28.2 25.1, 33.1 and 8.0 days were obtained for desmedipham in Speyer 2.2, Sandy Loam, Acidic Clay Loam and Alkaline Clay Loam.

Executive summary:

The degradation rate of [aniline- UL-¹⁴C] and [phenoxy- UL-¹⁴C] desmedipham was studied in the dark in 4 soils (Speyer 2.2: a sandy loam, acidic clay loam and alkaline clay loam) for up to 100 days at 21 °C, at 40 % of MWHC). The application rate was 918.4 μg a.s/kh (field rate of 0.69 kg as/ha). The non-normalised best fit DT₅₀ value of 28.2, 25.1, 33.1 and 8.0 days were obtained in Speyer 2.2, a sandy loam, acidic clay loam and alkaline clay loam.

Reference 2

Endpoint:

biodegradation in soil, other

Type of information:

calculation (if not (Q)SAR)

Remarks:

Kinetic evaluation

Adequacy of study:

key study

Study period:

2016-06-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

other: FOCUS guidance

Version / remarks:

2006

GLP compliance:

no

Remarks:

GLP is not relevant for studies following FOCUS guidance to calculate endpoints.

Specific details on test material used for the study:

The test material is desmedipham.

Details on experimental conditions:

The behaviour of desmedipham and its principal soil metabolite, EHPC under laboratory conditions was investigated in agricultural soils (Bruhl [1978]; Celorio [1985a]; Forster, [1991]: Mackie et al, [1991]; and Sadowsky-Dunkmann, [1993], with some duplication).

The calculations were done on a Dell Optiplex GX280 computer using the operation system Windows XP, Service Pack 2. The kinetic modelling analysis and statistical analysis were done employing MatLab (2005), Version 7.0.4.365 [KinGUI version 2.1]. Error tolerance was set to 1E-5 and all fits were allowed to converge (i.e., no constraint on number of iterations). Normalisation of kinetic parameters was performed using Microsoft® Excel spreadsheets, where the relevant equations had been implemented.

Key result

DT50:

62.8 d

Temp.:

12 °C

Remarks on result:

other: Calculated

DT50:

29.6 d

Temp.:

20 °C

Remarks on result:

other: Median DT50 value normalised to 20 °C

Transformation products:

not measured

Details on results:

The first-order kinetic parameters suitable for modelling and derived from the evaluation for desmedipham are given in Table 1. Soil degradation DT50 values for desmedipham ranged from 9.4 d to 216 d, with a median DT50 of 29.6 d for safety assessment.

The first-order kinetic parameters suitable for modelling and derived from the evaluation for desmedipham are given in Table 2. These data are presented for each experiment and for the experimental conditions. The data have then been normalised to pF2 and 20 °C, as recommended by FOCUS (2002), using the measured soil MWHC as given in the studies.

Table 1: Soil degradation DT50 values of desmedipham, according to FOCUS Kinetics (2006), at pF2 and 20 °C (combining equivalent soils and conditions).

Study	Soil Texture	Model fitted:	DT50 [d]	Comments
Bruehl, 1978	loamy sand	FOMC	58.5 ^1	Same soils, two curve fits, with different labels
	sandy loam	SFO	216.2 ^2	Same soils, two curve fits, with different labels
Forster, 1991	sandy loam	SFO	9.7	Single soil and conditions
Mackie et al, 1991	loamy sand	SFO	31.0	Single soil and conditions
	sandy loam	SFO	27.6
	clay loam	SFO	36.4
	clay loam	FOMC	9.4
Sadowsky- Dunkmann, 1993	sand	DFOP	28.2	Single soil and conditions
Geometric mean:			31.7
Arithmetic mean:			52.1
Median:			29.6

¹ Geomean of two values. ² Geomean of two radiolabels recalculated by the RMS.

 

Table 2: Soil degradation DT50 values of desmedipham, according to FOCUS Kinetics (2006), at experimental conditions.

Study	Location / Soil	Soil moisture [%MWHC]	T° of study	Model fitted:	DT50 [d]	Corr. DT50 1 [d]
Bruehl, 1978	Neuhofen, DE	86	24 °C	FOMC	38.1	55.7
	Hatzenbuehl, DE	58	24 °C	SFO	128	185.8
	Neuhofen, DE	86	24 °C	FOMC	42.0	61.4
	Hatzenbuehl, DE	58	24 °C	SFO	172.0	184.1
Forster, 1991	DE Std soil 2.3	75% of 1/3rd Bar	21 °C	SFO	8.8	9.7
Mackie et al, 1991	Speyer 2	40	21 °C	SFO	28.2	31.0
	Sandy loam	40	21 °C	SFO	25.1	27.6
	Acidic clay loam	40	21 °C	SFO	33.1	36.4
	Alkaline clay loam	40	21 °C	FOMC	9.7	9.4
Sadowsky- Dunkmann, 1993	DE Standard soil 2.1	40	20 °C	DFOP	28.2	28.2

¹ Normalised to pF2 and 20 °C 

 

 

Executive summary:

The degradation rates of desmedipham and its major degradation product EHPC in soil were studied using two different radiolabel positions for desmedipham, [aniline-UL-14C] and [phenoxy-UL-14C], and one radiolabel position for the degradation product EHPC, [phenyl-ring-UL-14C]. The studies have been performed in a number of soils in the dark in the laboratory at temperatures between 15 to 25 °C and different soil moistures. For desmedipham and EHPC kinetic evaluations of the degradation behaviour in soil under aerobic conditions in the dark in the laboratory have been performed according to FOCUS kinetics (2006) to derive kinetic parameters suitable for modelling purpose and environmental risk assessment.

The first-order kinetic parameters suitable for modelling and derived from the evaluation for desmedipham are given in Table 1. Soil degradation DT50 values for desmedipham ranged from 9.4 d to 216.2 d, with a median mean DT50 of 29.6 d. 

Description of key information

The soil end points following FOCUS kinetics guidance are the modelling half life of 62.8 days (based on the median value using SFO where possible calculated to at 12 °C), or the persistence half life of 67.3 days or (based on the best fit kinetics calculated to at 12 °C). For simplicity the worst case of these will be used in the chemical safety assessment.

In the table below all available studies are listed. For some studies only the results are presented since they are not considered relevant due to the reasons given under “Assessment”. All available studies have been evaluated within the scope of Plant Protection Regulation in the respective Draft Renewal Assessment Report (DAR) under Regulation (EC) 1107/2009.

Test type	Result	Assessment	Reference
Kinetics report carried out in line with FOCUS guidelines	A DT50 median value of 29.6 days at 20 °C for modelling (62.8 days at 12 °C)	Key study	Chapple (2014)
Study carried out in line with OECD 307	Prior to GLP, some reporting issues but result used in calculation of DT50 endpoints	Supporting study	Bruehl (1978)
Study carried out in line with OECD 307 using German standard soil 2.3	DT50 8.8 days (at 20 °C)	Supporting study	Forster (1991)
Study carried out in line with OECD 307 using 4 soils	DT50 values 28.2, 25.1, 33.1, 8.0 non normalised (20 °C)	Key study	Mackie (1991)
Study carried out in line with OECD 307	DT50 28.2 days at 20 °C (modelling), and 3.7 days at 20 °C (trigger)	Supporting study	Sadowsky-Dunkmann (1993)
Carried out using non specified EPA and Dutch guidelines using Soil 162	DT50 of 12.1 days at 15 °C and 5.8 days at 25 °C for trigger/modelling	Study non GLP, radioactive recovery was below 70%, not accepted by the RMS under PPP evaluation.	Celorio (1985)
Carried out using non specified EPA and Dutch guidelines using Soil 161	DT50 of 15.5 days at 15 °C and 8.0 days at 25 °C for trigger/modelling	Study non GLP, soil organic C (8.78%) above max recommended OECD level of 2.5%. Not considered a representative agricultural soil and not considered to be valid in the DAR	Celorio (1985)
Carried out using non specified guidelines using Morrison sandy loam and Hagerstown silt loam	No result specified	Partly performed outdoors in open jars- not considered to be valid in the DAR	Ercegovich (1974)
Carried out using non specified guidelines Dissipation of desmedipham in two standard soils (Neuhofen and Hatzenbüh)	DT50 value for the Hatzenbühl soil was 123 days and an estimated DT50 value for Neuhofen soil 24 days.	Short method description and not considered to be valid in the DAR	Ottnad (1975)
Carried out using non specified guidelines using German standard 2.2 soil	DT50 13.7 days (20 °C modelling), 5.9 days (20 °C trigger)	Radioactive recovery was < 90%, the first samples were only taken after 7 days, no duplicates were use- not considered to be valid in the DAR	Bruehl (1981)
Soil Dissipation Of Desmedipham, Laboratory And Field Trials	No result specified.	Previous evaluation not found in DAR (2000) or Addendum 3 to DAR (2003).	Anon (1989)
Kinetics report for old studies Aerobic Decomposition of Desmedipham in Soil	The non-normalised best fit (SFO) geomean DT50 values for [phenoxy-UL-14C] and [aniline-UL-14C]desmedipham were 12.4 and 14.8 days in Neuhofen soil, respectively, and 126 and 127.2 days in Hatzenbühl soil, respectively. Only in soil Neuhofen a SFO DT50 value of 5.2 days for EHPC were obtained.	The kientics assessment was carried out prior to FOCUS guidelines- so has been superseded.	Bruehl (1993)
Anaerobic conditions	No result specified.	Recovery was low, no confirmation of anaerobic system- not considered to be valid in the DAR	Bruehl (1982)
Carried out following SETAC guidelines (and following OECD 307) Anaerobic soil degradation in a silty clay loam soil	The SFO DT50 and DT90 for [14C-phenoxy] desmedipham were estimated to be 0.57 and 1.90 days and DT50 and DT90 for [14C-aniline] desmedipham 0.41 days and 6.09 days in the total system, respectively.	Anaerobic degradation not relevant -> Supporting study. Kinetics were not calculated according to FOCUS guidelines	Sabourin (2003)
Carried out following SETAC guidelines (and following OECD 307) Anaerobic soil degradation in a sandy loam soil	The DT50 values were 0.004 and 0.011 days for aniline and phenoxy labelled desmedipham in soil LUFA 3A under anaerobic conditions, respectively. The DT50 values for aniline and EHPC were 2.2 and 2.5 days, respectively. For phenyl urethane the sampling regime did not allow calculation of DT50 values.	Anaerobic degradation not relevant -> Supporting study. Kinetics were calculated according to FOCUS guidelines	Derz (2005)
Supplementary report to Sabourin (2003)	Re-analysis of the phenoxy labelled desmedipham extracts under different HPLC conditions has shown that the weakly retained components in the original report chromatograms were multi-component, consisting of at least 3 compounds. It has also been shown that in the aniline labelled desmedipham experiment the weakly retained peaks were multi-component.	Anaerobic soil degradation study -> supplementary report	Oddy et al (2004)
Soil dissipation study (US)	No result specified.	The study was not considered valid due to inaccurate reporting and inadequate description of the study methods.	Jenny (1973)
Soil dissipation study (DE) treated with co-formulation	Range of DissT50 4.8 to 8.8 days	Valid field study but not re-evaluated in DAR	Moede (1990)
Soil dissipation study (US) treated with formulation	Range of DissT50 7.6 to 41.5	Valid field study but not re-evaluated in DAR	Castro (1991)
Carried out using non specified guidelines for Aged soil leaching	No result specified.	Invalid due to incorrect leaching solvent and amount applied	Forster (1992)
Aged soil leaching	No result specified.	Valid but not included in DAR	Mackie (1992)
Carried out to BBA Guideline IV, 4-2 (1986) leaching of desmedipham in German standard soil	Over 85 % of the material recovered, remained in the top 10 cm. No parent compound was found in leachate which contained 3.0-3.5 % of AR.	Aged leaching not required for REACH	Sadowsky-Dunkmann (1993)

DAR (2000): Desmedipham Draft Assessment Report 2000

Addendum 3 to DAR (2003):Desmedipham Addendum 3 (2003) to Draft Assessment Report 

Persistence Assessment

Persistence DT₅₀ values in soil are available from the DAR for desmedipham and metabolites (taken from the crop protection dossier) - but these values do not take non-extractable residues into account, so cannot be directly compared to the trigger values under REACH.

The addition of NER to the concentration of desmedipham, does not give an acceptable value for DT₅₀ (following FOCUS guidance) as the levels of NER are rising throughout the study.

However, the amount of ¹⁴CO₂ released during the study period can be considered for the assessment of persistency. For the four soils at the end of the study on day 100 levels of ¹⁴CO₂ range from 21.4 to 37.8 % AR. This indicates that less than 50 % of radioactive material has been mineralised during the study i.e. the mineralisation DT₅₀ is > 100 days. Hence at 12 °C the DT₅₀ will be > 200 days. This is greater than the P trigger of > 120 days or the vP trigger of > 180 days in soil.

Key value for chemical safety assessment

Half-life in soil:

67.3 d

at the temperature of:

12 °C