Desmedipham

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2004-07-26 to 2004-12-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

July 2002

Deviations:

not specified

Principles of method if other than guideline:

Definite amounts of plants and fronds were exposed to different concentrations of the test item. Frond numbers were counted to determine NOEC-, LOEC- and EC50-values. Biomass dry weight was determined after 14d. A semi-static test method was applied.

GLP compliance:

yes

Specific details on test material used for the study:

The test material is a white solid.

Analytical monitoring:

yes

Details on sampling:

The concentrations of the active substance, Desmedipham and its metabolite Ethyl(3-hydroxyphenyl)carbamate (EHPC) were analysed on days 0, 2, 9 and 12 (freshly prepared solutions) and on days 2, 5, 12 and 14 (old solutions) via HPLC-UV.

Vehicle:

no

Test organisms (species):

Lemna minor

Details on test organisms:

TEST ORGANISM
- Common name: Duckweed (Lemna minor)
- Method of cultivation: The species was bred in the testing facility. Density was kept low to prevent conglomerates of plants on the surface. At least once per week, plants were transferred to freshly prepared growth medium. Growth media and breeding vessels were autoclaved before use to enable the breeding of axenic cultures.

Test type:

semi-static

Water media type:

other: Swedish standard (SIS) medium according to guideline

Limit test:

no

Total exposure duration:

14 d

Test temperature:

23 – 25°C

pH:

6.51 - 7.51

Nominal and measured concentrations:

Nominal concentrations: 0.032, 0.1, 0.32, 1.0 and 3.2 mg a.s./L
Measured concentrations: 1.92, 0.56, 0.19, 0.059 and 0.017 mg a.s./L

Details on test conditions:

TEST SYSTEM
- Test vessel: Crystallisation dishes with a volume of 500 mL, covered with glass tops and filled with 200 mL test solution were used in the test.
- Type: closed
- No. of colonies per vessel: 3 colonies
- No. of fronds per colony: 4 fronds
- No. of vessels per concentration (replicates): 3 replicates
- No. of vessels per control (replicates): 3 replicates

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Light intensity and quality: 6500 - 10000 Iux

Reference substance (positive control):

yes

Remarks:

Zinc chloride

Key result

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

0.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other: based on geometric mean concentrations from the re-evaluated report.

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

0.85 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other: based on initial measured mean concentrations from the re-evaluated report.

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

0.5 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other: based on mean measured concentrations from the initial study report.

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0.05 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other: based on geometric mean measured concentrations from the re-evaluated report.

Details on results:

Analytical results
The recovery rates, calculated as a sum of the mean measured desmedipham and EHPC, were 92 ± 7% in the fresh and 93 ± 8% (n=20) in the old solution. The endpoints which were based on initial mean measured concentrations was recalculated to reflect the geometric mean measured concentrations of desmedipham, and this is documented in the amended report M-545827-01-1.

Biological results
The growth inhibition effects of the test item are presented in Table 2. The calculated endpoints are summarized in Table 3 based on nominal concentration of desmedipham and in Table 4 based on arithmetic mean measured concentration of desmedipham.

The 7 day ErC50-value was 0.85 mg a.s./L based on nominal concentrations of desmedipham only without its metabolite, and 0.5 mg a.s./L based on arithmetic mean measured concentrations of desmedipham. The 7 day NOErC was 0.1 mg a.s./L (nom.). The 7 day ErC50-value was 0.40 mg a.s./L based on geomean measured concentrations of desmedipham.

Results with reference substance (positive control):

As reference test, an acute toxicity study of Zinc chloride (ZnCl2) to the monocotyledon Lemna minor was determined over a period of 7 days. The tested concentrations were 0.32, 1, 3.2, 10 and 32 mg zinc chloride/L. The EC50-values with 95% confidence intervals for inhibition of specific growth rate (ErC50) after 72 h for the reference item was 4.6 (0.8 – 27.3) mg zinc chloride/L.

Table 2: Growth inhibition in Lemna minor after 7 days 

Arithmetic mean measured concentration [mg/L] (nom)	Log Biomass integral*	Inhibition of log biomass [%]	Specific Growth rate*	Inhibition of specific growth rate [%]	Doubling time [d]
Control	7.86 ± 0.76		0.35 ± 0.02		1.99 ± 0.10
0.017 (0.032)	8.11 ± 0.50	-3.24 ± 6.31	0.35 ± 0.00	-0.26 ± 0.77	1.98 ± 0.02
0.059 (0.1)	8.32 ± 0.50	-5.82 ± 6.35	0.36 ± 0.01	-3.55 ± 1.61	1.92 ± 0.03
0.19 (0.32)	6.08 ± 0.78	22.7 ± 9.92	0.26 ± 0.01*	24.4 ± 3.53	2.63 ± 0.13
0.56 (1.0)	3.49 ± 0.33*	55.6 ± 4.15	0.13 ± 0.02*	62.7 ± 5.06	5.39 ± 0.78
1.92 (3.2)	2.05 ± 1.30*	73.9 ± 16.5	0.09 ± 0.09*	75.1 ± 18.4	10.7 ± 5.55

* One Way Analysis of Variance (ANOVA, DUNNETT'S method) (biomass integrals) and the BONFERRONI t-test

(growth rates), respectively, were carried out for the determination of statistically significant differences compared to control replicates.

 

Table 3: Effect after 2, 5, 7, 9, 12 and 14 d. based on nominal concentrations of the test item

	2 days	5 days	7 days	9 days	12 days	14 days
		Inhibition of specific growth rate [mg a.s./L]
ErC50 value	0.95	0.88	0.85	0.60	0.51	0.60
95 % C.I.	0.28 – 3.15	0.20 – >3.2*	0.18 – >3.2*	0.15 – 2.32	0.17 – 1.50	0.22 – 1.61
LOEC	1.0	0.32	0.32	0.32	0.32	0.32
NOEC	0.32	0.1	0.1	0.1	0.1	0.1

*Highest concentration level = 3.2 mg a.s./L

 

Table 4: Effect in after 2, 5, 7, 9, 12 and 14 d. based on arithmetic mean measured concentrations of desmedipham

	2 days	5 days	7 days	9 days	12 days	14 days
		Inhibition of specific growth rate [mg a.s./L]
ErC50 value	0.55	0.49	0.50	0.35	0.30	0.35
95 % C.I.	0.17- 1.84	0.12- >1.92*	0.10- >1.92*	0.09- 1.36	0.10- 0.87	0.13- 0.94
LOEC	0.56	0.19	0.19	0.19	0.19	0.19
NOEC	0.19	0.059	0.059	0.059	0.059	0.059

*Highest concentration level = 1.92 mg a.s./L

Validity criteria fulfilled:

yes

Remarks:

Doubling time of frond number in the control group was <2.5 days (60 hours).

Conclusions:

The study fulfilled the validity criteria for control growth and the pH-value was within the acceptable limits set in OECD TG 221 (2006). The 7 day ErC50-value was 0.85 mg a.s./L based on nominal concentrations of desmedipham only without its metabolite, and 0.5 mg a.s./L based on arithmetic mean measured concentrations of desmedipham. The 7 day NOErC was 0.1 mg a.s./L (nom.). The 7 day ErC50-value was 0.40 mg a.s./L based on geomean measured concentrations of desmedipham.

Executive summary:

The toxicity of desmedipham to the duckweed Lemna minor, was determined. The duckweeds were exposed to nominal concentrations of 0.032, 0.1, 0.32, 1.0 and 3.2 mg a.s./L alongside a control. The 7 day E_rC₅₀ value was 0.40 mg a.s./L based on geometric mean measured concentrations of desmedipham.

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2012-07-23 to 2013-07-09

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

study was performed according to the OECD TG 221, but the study followed in principle the OECD TG 239

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The test material is a white powder.

Analytical monitoring:

yes

Details on sampling:

Samples of were taken for analysis of desmedipham and EHPC by HPLC on days 0, 4, 11 and 14.

Vehicle:

yes

Remarks:

Acetone (0.1 m/L)

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Differential loading: The test system consisted of three replicate test vessels per treatment group. Nominal (mean measured) concentrations were , 15 (15.2), 48 (44.0), 150 (125), 490 (435), 1560 (1474) and 5000 (4175) µg a.s./L, respectively. Each replicate contained five plants for a total of 15 plants per group. All plants within a replicate were planted into a single 125x65 mm crystallization dish containing 550 grams of artificial sediment. The rooted aquatic plants were submerged in 4-L beakers.
- Controls: control and solvent control.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Acetone
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): 0.1 mL acetone/L
- Evidence of undissolved material (e.g. precipitate, surface film, etc.):None. Test solutions appeared clear and colorless.
- Other relevant information: The test material was shown to be stable in acetone. For each test concentration a separate stock solution was prepared prior to the start of the study. These stocks were used for the preparation of test solutions on days 0, 4, 6, 8 and 11. Sediment used for testing was prepared following the OECD 218 sediment preparation recommendation. Instead of adding distilled water to wet the sediment, 20 XAAP media was used to provide shoots with a fertilizer source.

Test organisms (species):

Myriophyllum spicatum

Details on test organisms:

TEST ORGANISM
- Common name: Myriophyllum spicatum

ACCLIMATION
- Acclimation period: 7 days

Test type:

semi-static

Water media type:

other: Hard Processed Water (blended spring and reverse osmosis water)

Limit test:

no

Total exposure duration:

14 d

Remarks on exposure duration:

Exposed over 14 days with observations carried out at regular intervals.

Test temperature:

19.48 to 20.45°C

pH:

8.1 to 9.8

Dissolved oxygen:

7.8 to 11.5 mg/L

Nominal and measured concentrations:

Nominal (mean measured) concentrations were control, solvent control (0.1 mL acetone/L), 15 (15.2), 48 (44.0), 150 (125), 490 (435), 1560 (1474) and 5000 (4175) µg a.s./L, respectively.

Details on test conditions:

Lighting: 7980 to 10,720 lux (mean = 9160 lux)
Photoperiod: 16 hours light, 8 hours dark
Test vessels: Shoots within a replicate are planted in sediment within a 650 mL borosilicate glass crystallization dish housed in a 4-L glass beaker.
Test medium: Hard Processed Water (blended spring and R.O. water)

Key result

Duration:

14 d

Dose descriptor:

other: ErC50

Effect conc.:

> 0.05 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

shoot length

Remarks on result:

other: based on recalculated mean

Key result

Duration:

14 d

Dose descriptor:

other: NOErC

Effect conc.:

0.002 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Remarks on result:

other: based on recalculated mean

Duration:

14 d

Dose descriptor:

other: NOErC

Effect conc.:

0.015 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

other: ErC50

Effect conc.:

> 5 000 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

other: LOErC

Effect conc.:

48 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Details on results:

Mean measured recoveries for sum of desmedipham and EHPC measured from representative samples of new and old solutions ranged from 83 to 101% of nominal concentrations. Results are based on nominal test concentrations of desmedipham. The measured recoveries showed that desmedipham was completely hydrolysed in the old solutions. Sediment samples were not collected for chemical analysis.

Active growth of the control plants during the 14 day exposure period was demonstrated by an average total shoot length yield of approximately 28.3 cm. Plants in the control, solvent control and all treatment groups appeared normal throughout the study. Observation of roots upon study termination were normal compared to the controls in all treatment groups. During the statistical analysis of the data, it was determined that replicate A in the solvent control group was an outlier. This replicate was therefore excluded in further data analysis

Total Shoot Length Growth Rate
Total plant shoot length growth rate was analyzed at test termination on study day 14. Data analysis showed a statistically significant difference, in comparison to the pooled control data, in the five highest treatment levels. Percent inhibitions as compared to the pooled control group were 11.1, 17.3, 18.5, 16.6, 26.9 and 29.2% for the 15, 48, 150, 490, 1560 and 5000 µg a.s./L test
groups, respectively.

Total Plant Wet Weight Growth Rate
Total plant wet weight growth rate was analyzed at test termination on study day 14. Data
analysis showed a statistically significant difference, in comparison to the pooled control data, in
the two highest treatment levels. Percent inhibitions as compared to the pooled control group
were 12.3, 13.9, 12.8, 3.1, 26.2 and 38.9% for the 15, 48, 150, 490, 1560 and 5000 µg a.s./L test
groups, respectively.

Total Plant Dry Weight Growth Rate
Total plant dry weight growth rate was analyzed at test termination on study day 14. Data
analysis showed a statistically significant difference, in comparison to the pooled control data, in
the two highest treatment levels. Percent inhibitions as compared to the pooled control group
were 9.5, 18.6, 7.0, 6.0, 29.2 and 37.7% for the 15, 48, 150, 490, 1560 and 5000 µg a.s./L test
groups, respectively.

Total Shoot Length Yield
Shoot length yield was analyzed at test termination on study day 14. Data analysis showed a
statistically significant difference, in comparison to the pooled controls at all treatment levels.
Percent inhibitions as compared to the pooled control group were 26.0, 32.2, 34.4, 28.7, 45.8 and
51.6% for the 15, 48, 150, 490, 1560 and 5000 µg a.s./L test groups, respectively.

Total Plant Wet Weight Yield
Total plant wet weight yield was analyzed at test termination on study day 14. Data analysis
showed a statistically significant difference, in comparison to the pooled control data, in the two
highest treatment levels. Percent inhibitions as compared to the pooled control group were 23.4,
25.0, 24.7, 7.0, 43.8 and 59.3% for the 15, 48, 150, 490, 1560 and 5000 µg a.s./L test groups,
respectively.

Total Plant Dry Weight Yield
Plant dry weight yield was analyzed at test termination on study day 14. Data analysis indicated
a statistically significant difference, in comparison to the pooled control data, in the two highest
treatment levels as well as the 48 µg a.s./L treatment group. However, the effect in the 48 µg
a.s./L treatment group is not considered to be biologically relevant since the next two higher
concentrations has lower inhibition and no statistically significant effect. Percent inhibitions as
compared to the pooled control group were 20.4, 34.9, 16.3, 15.2, 51.1 and 60.4% for the 15, 48,
150, 490, 1560 and 5000 µg a.s./L test groups, respectively.

Analytical Limit of Quantification: 0.5 µg a.s./L for each analyte

 

The E_rC₅₀s for each of the three endpoints (shoot length, wet weight and dry weight) were determined to be greater than the highest test concentration. The lowest NOE_rC in the 14 day exposure of the rooted aquatic macrophyte Myriophyllum spicatum to Desmedipham technical was obtained for shoot length growth rate. The statistical NOE_rC, LOE_rC and E_rC₅₀ for this endpoint were 15, 48 and >5000 µg a.s./L, respectively. The lowest extrapolated E_rC₅₀ of 6965 µg a.s./L was obtained for the wet weight endpoint. The 14-day E_rC₅₀ was recalculated based on geometric mean concentrations of desmedipham, and it is documented in the report M-545827-01-1.

 

See "Attachments" in "Overall remarks, attachments" for the following tables and figures;

 

Table 7: Growth Rates For Plant Shoot Length, Wet Weights and Dry Weights During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Table 8: Mean Yields For Plant Shoot Length, Wet Weights and Dry Weights During the Exposure of Myriophyllum spicatum to Desmedipham Technical

 

Figure 1: Minimum, Maximum and Mean Values for Plant Shoot Length Growth Rate During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Figure 2: Minimum, Maximum and Mean Values for Wet Weight Growth Rate During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Figure 3: Minimum, Maximum and Mean Values for Dry Weight Growth Rate During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Figure 4: Minimum, Maximum and Mean Values for Plant Shoot Length Yields During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Figure 5: Minimum, Maximum and Mean Values for Plant Wet Weight Yields During the Exposure of Myriophyllum spicatum to Desmedipham Technical
Figure 6: Minimum, Maximum and Mean Values for Plant Dry Weight Yields During the Exposure of Myriophyllum spicatum to Desmedipham Technical

Validity criteria fulfilled:

yes

Remarks:

Mean total shoot length and fresh weight in the control group during the 14 day exposure doubled within 14 days. Mean CV for shoot fresh weight in the control was <35% (<14% obtained). There were no visual symptoms of chlorosis in the control.

Conclusions:

The study was performed according to the OECD TG 221 (Lemna growth inhibition test), but the study followed in principle the OECD TG 239 (2014; Water-sediment Myriophyllum spicatum toxicity test) except that the replication was smaller than recommended by OECD TG 239 (2014): six for control and four for test levels. However, the study was performed before the test guideline adoption in 2014 and the replication in the test allowed statistical significance to be observed even at second lowest treatment level. The pH range increased more than the required ± 1.5. This is however not considered to invalidate the study since the criteria for control growth was met. Otherwise the study fulfilled the criteria set in OECD TG 239 (2014) and therefore the study is considered valid. The 14 day ErC50 value was >5 mg a.s./L, based on nominal concentrations of desmedipham and >0.05 mg a.s./L based on geometric mean measured concentrations of desmedipham. The 14 day NOErC value was 0.002 mg a.s./L based on mean measured concentration of desmedipham.

Executive summary:

The toxicity of desmedipham to aquatic macrophyte, Myriophyllum spicatum was determined. Macrophytes were exposed to nominal concentrations of 15, 48, 150, 490, 1560 and 5000 µg a.s./L alongside a solvent control and culture medium control over a 14-day period. The 14 day E_rC₅₀ value was >5 mg a.s./L, based on nominal concentrations of desmedipham and >0.05 mg a.s./L based on geometric mean measured concentrations of desmedipham. The 14 day NOE_rC value was 0.002 mg a.s./L based on mean measured concentrations of desmedipham.

Reference 3

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2002-09-13 to 2002-11-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

1998

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: U. S. Environmental Protection Agency guideline 123-2

Version / remarks:

United States Environmental Protection Agency (EPA) Federal Insecticide, Fungicide, Rodenticide Act (FIFRA); Good Laboratory Practice Standards; Final Rule; 40 CFR Part 160; Federal Register Vol. 54, No. 158 34052-34074

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The test material is in a light grey powder form.

Analytical monitoring:

yes

Details on sampling:

Water samples for chemical analysis of each freshly prepared treatment concentration were taken at Day 0 (test initiation), Day 2 and Day 4. Old samples were taken on Day 2, Day 4 and Day 7 (test termination). Freshly prepared samples were taken from the original parent stock solutions, while old samples were composites of treatment replicates. All samples were analyzed by High Performance Liquid Chromatography (HPLC) with ultraviolet detection (UV) for quantification of desmedipham.

Vehicle:

yes

Remarks:

0.1 mL DMF/L

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A primary (1°) stock solution was prepared at a nominal concentration of 60 mg/mL by weighing 305.5 mg of test substance into a 5 mL volumetric flask and bringing to volume with DMF. A 6.0 mg/L secondary stock was prepared by the addition of 0.4 mL of the primary stock (60 mg/mL) and into 4-liters of 20X-AAP medium. Following preparation, the secondary stock was stirred for approximately 10 minutes at test temperature. The secondary stock was used to prepare each of the nominal concentrations by appropriate dilutions.
- Controls: a control and solvent control.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): DMF (Dimethylformamide)
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): A white flaky precipitate was visible on the water surface and therefore the secondary stock was filtered through a 0.45 µm filter. No precipitate was visible following the filtering procedure.
- Other relevant information: The test chambers were autoclaved 1200-mL glass crystallizing dishes containing 500 mL of test solution. Approximate test chamber dimensions were 7.5-cm (H) x 15.0-cm (diameter) with an approximate 3.1 cm solution depth. Test chambers were produced in triplicate for the treatment concentrations and control. Plants with three fronds were randomized one at a time until each chamber contained 5 plants for a total of 15 fronds. All dishes were positioned on a bench within an environmental chamber by randomized assignment. Test chambers were newly randomized at each renewal period on Day's 2 and 4. Test chambers were covered with glass sheets to prevent evaporation and entry of foreign materials. Frond counts and abnormal appearance were visually evaluated with the aid of an illuminated light box on Day 2, 4, and 7.

Test organisms (species):

Lemna gibba

Details on test organisms:

Cultures were maintained in the Ecotoxicology Laboratory at test temperature and under continuous light. The plants were cultured and tested in 20X-AAP (Algal Assay Procedure) nutrient medium utilizing aseptic technique. The medium was prepared with deionized water (reverse osmosis) and reagent grade chemicals. These contain no known contaminants believed to be at levels that would have interfered with this study. All glassware used in the study was autoclaved prior to use. Medium components were autoclaved prior to preparation of 20X-AAP. The 20X-AAP nutrient media was filtered through a 0.45/µm membrane filter prior to use in the test.

Plants were maintained in cultures for 12 days under the following conditions prior to the study:
Mean Temperature: 25.3°C (SD = 0.06; range = 25.1 to 25.5°C)
Light: Continuous light, provided by warm-white fluorescent tubes
Medium: 20X-AAP algal growth medium

Test type:

semi-static

Water media type:

other: 20X-AAP growth medium

Limit test:

no

Total exposure duration:

7 d

Test temperature:

Mean temperature of 24.7°C (ranging from 23.0 to 25.0°C).

pH:

7.7 to 8.8

Dissolved oxygen:

6.0 to 8.3 mg/L (74 to 100% saturation).

Conductivity:

1500 to 1900 µmhos/cm (µS/cm).

Nominal and measured concentrations:

Nominal concentrations of 0.03, 0.09, 0.25, 0.72, 2.08, and 6 mg a.s./L alongside a control and solvent control.
Mean measured concentrations: 0.02, 0.07, 0.18, 0.52, 1.71, and 5.2 mg a.s./L (71 to 86% of nominal).

Details on test conditions:

Three replicates of Lemna gibba were exposed to nominal concentrations of control, solvent control(0.1 ml dimethylformamide /L), 0.03, 0.09, 0.25, 0.72, 2.08 and 6.0 mg a.s./L for a 7-day period in a static-renewal system.5 uniform healthy-looking plants (colonies) with 3 fronds each were used in eachtest vessel henceinitial frond number was 15. Test solutionswere renewed on days 2 and 4.

Test water was a 20X-AAP synthetic medium with a mean temperature of 24.7 °C anddissolved oxygen content of 7.2 mg/L. Light intensity ranged from 6500 to 7200 Lux.

Chemical analysis of the freshly prepared (days 0, 2 and 4) and aged media (days 2, 4 and 7) was performed for all test concentrations by HPLC-UV detection.LOQ was 0.02 mg/L.

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

0.52 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

> 0.229 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other:

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

> 5.2 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other:

Details on results:

Analytical results
The method recovery was 92%. The mean measured desmedipham concentration in the fresh test solution ranged from 71 to 86% of nominal concentrations. Due to rapid hydrolysis, no residues were detected in the aged test solutions. The results were based on mean measured initial concentrations. However, in the amended report M-545827-01-1, the endpoints were recalculated to reflect the geometric mean measured concentrations of desmedipham (See "Attachments" in "Overall remarks, attachments" for “Geometric mean measured concentrations of desmedipham”).

Biological results
A t-test determined that control and solvent control results were not significantly different and therefore the results for controls were pooled. Both the 7 d ErC50 and EbC50 values were above 5.2 mg/L based on mean measured initial concentration of desmedipham. Also, the 7 d NOEC values for growth rate, biomass and frond dry weight were 0.52 mg/L. The 7 d LOEC value was 1.71 mg/L. The 7 d ErC50 based on geometric mean measured concentration of desmedipham was >0.229 mg a.s./L.

See "Attachments" in "Overall remarks, attachments" for the figure and tables.

Validity criteria fulfilled:

yes

Remarks:

Doubling time of frond number in the control group was <2.5 days (60 hours).

Conclusions:

The study was considered valid and re-evaluation showed that the OECD TG 221 validity criteria for control growth were met. The 7 d ErC50 and EbC50 values were >5.2 mg/L based on mean measured initial concentration of desmediphamand ErC50 >0.229 mg a.s./L based on geometric mean measured concentration of desmedipham.

Executive summary:

The toxicity of desmedipham to Lemna gibba G3 was determined. The duckweeds were exposed to nominal concentrations of 0 0.03, 0.09, 0.25, 0.72, 2.08, and 6 mg a.s./L alongside a control and solvent control over a 7-day period. The 7-day E_rC₅₀ value was >5.2 mg a.s./L, based on nominal concentrations of desmedipham and >0.229 mg a.s./L based on geometric mean measured concentrations of desmedipham.

Reference 4

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-03-09 to 2012-12-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Version / remarks:

March 23, 2006

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The test material is in a white powder form.

Analytical monitoring:

yes

Details on sampling:

Quantitative amounts of desmedipham and its metabolite EHPC were measured in all freshly prepared test levels on day 0, 2, and 5 and additionally in all aged test levels on day 2, 5, and 7 of the exposure period by HPLC-MS/MS.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
13.1 mg of the test substance ad 1300 mL nutrient medium was prepared immediately prior to the test, on days 0, 3 and 5. The stock solution was well agitated on a magnetic stirrer for 30 minutes and was additionally ultrasonicated for 10 minutes before further use. An adequate amount of the stock solution was transferred to a dilution series to obtain the concentration levels used in the study. The test item was applied into the freshly prepared test medium on day 0, 3, and 5.

Test organisms (species):

Lemna gibba

Details on test organisms:

TEST ORGANISM
- Common name: Lemna gibba
- Strain: G3
- Method of cultivation: The respective documentation for the stock culture is missing for this study. The effects are measured and documented by photo-analysis (LemnaTec Scanalyzer). This photo documentation was used to check the Lemna plants used within this study visually. The visual check of the photo-documentation revealed that healthy and suitable plants were used for the performance of the test. The validity criteria for the growth of the control was fulfilled, this demonstrates that the used Lemna plants were of acceptable quality for the study. This deviation from the normal procedures was observed and is documented within the raw data.

Test type:

semi-static

Water media type:

other: 20X - AAP medium

Limit test:

no

Total exposure duration:

7 d

Remarks on exposure duration:

Exposed over 7 days with visual observations made on study days 3, 5, and 7.

Test temperature:

22.8°C - 24.6°C

pH:

7.5 - 7.8

Nominal and measured concentrations:

Nominal test concentrations: 0 (control), 0.0780, 0.156, 0.313, 0.625, 1.25, 2.50, 5.00, and 10.0 mg a.s./L.
Geometric mean measured concentrations : 0.0074, 0.0107, 0.0149, 0.0208, 0.0295, 0.0409, 0.0579, and 0.1650 mg a.s./L (see Table B.9.2.7-12)

Details on test conditions:

- Three replicates of 12 fronds in each of Lemna gibba G3 per test concentration were exposed for 7 days under semi-static exposure conditions to the nominal concentrations of 0.0780, 0.156, 0.313, 0.625, 1.25, 2.50, 5.00 and 10.0 mg a.s./L in comparison to a water control.
- Quantitative amounts of desmedipham and its metabolite EHPC were measured in all freshly prepared test levels on day 0, 2, and 5 and additionally in all aged test levels on day 2, 5, and 7 of the exposure period by HPLC-MS/MS.
- The pH values ranged from 7.5 to 7.8 and the incubation temperature ranged from 22.8°C to 24.6°C over the whole period of testing at a continuous illumination of 8267 Lux.

Duration:

7 d

Dose descriptor:

other: NOErC

Effect conc.:

0.011 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond area

Remarks on result:

other: based on recalculated NOEC value from amended report.

Duration:

7 d

Dose descriptor:

other: ErC10

Effect conc.:

0.011 mg/L

95% CI:

0.066 - 0.162

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond number

Remarks on result:

other: based on calculated ErC10 value from amended report.

Key result

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

0.113 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

frond area

Remarks on result:

other: based on recalculated ErC50 value from amended report.

Duration:

7 d

Dose descriptor:

other: ErC50

Effect conc.:

8.41 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

frond area

Remarks on result:

other: based on ErC50 value from initial study report.

Details on results:

Analytical results
The analytical findings of the sum of desmedipham and EHPC in all freshly prepared test levels on days 0, 3, and 5 ranged between 110 and 125% of nominal concentrations (and between 101 and 125% based on desmedipham concentration). In aged test levels on days 3, 5, and 7, analytical findings ranged between 100 and 113% of nominal concentrations. All reported results are based on nominal values desmedipham. No desmedipham was detected in the aged medium.
The endpoint was recalculated based on geometric mean measured concentrations, and this is given in Table B.9.2.7-12.

Biological results
There were no visual effects observed in any of the test concentrations. The effects of desmedipham on mean growth rate of frond number and of total frond area are presented in Table B.9.2.7-13.
The ErC50 and ErC10 values are presented in Table B.9.2.7-14a and the EyC50 and EyC10 values in Table B.9.2.7- 14b. The initial ErC50 value was 8.41 mg a.s./L, and this was based on nominal concentrations of the test item. However, in the amended report M-594283-01-1, the ErC50 value was recalculated on the basis of geometric mean measured concentrations of desmedipham. The most sensitive endpoint was total frond area of plants resulting in a 7d-ErC50 value of 0.113 mg a.s./L, based on geomean measured concentration of desmedipham and the lowest ErC10 was 0.0114 mg a.s./L.

See "Attachments" in "Overall remarks, attachments" for the tables.

Validity criteria fulfilled:

yes

Remarks:

Doubling time of frond number in the control group was 1.7 days which is <2.5 days.

Conclusions:

The study is considered valid and a 7 d ErC50 value of 8.41 mg a.s./L was obtained, based on nominal concentrations of desmedipham, and a 7 d ErC50 value of 0.113 mg a.s./L based on geomean measured concentrations of desmedipham. The NOErC value was 0.0107 mg a.s./L based on geomean measured concentrations of desmedipham.

Executive summary:

The toxicity of desmedipham to Lemna gibba G3 was determined. The duckweeds were exposed to nominal concentrations of 0.0780, 0.156, 0.313, 0.625, 1.25, 2.50, 5.00 and 10.0 mg a.s./L alongside a water control over a 7-day period. The 7-day E_rC₅₀ value was 8.41 mg a.s./L, based on nominal concentrations of desmedipham and 0.113 mg a.s./L based on geometric mean measured concentrations of desmedipham. The NOErC value was 0.0107 mg a.s./L based on geometric mean measured concentrations of desmedipham.

Description of key information

Toxicity to aquatic plants: A study was conducted to determine the influence of Desmedipham on Myriophyllum spicatum over 14 days. Based on geometric mean measured concentrations, the 14-d E_rC₅₀ and NOEC were determined to be >0.05 mg/L and 0.002 mg/L, respectively.

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 species	Result	Assessment	Reference
Myriophyllum spicatum  (Eurasian watermilfoil)	14-d ErC50 >5 mg/L (initial measured, based on frond numbers)  14-d ErC50 >0.05 mg/L (geomean measured, based on frond numbers)  14-d NOErC = 0.002 mg/L (based on frond numbers)	Key study	Banman & Moore (2013) amended by Mihan (2016)
Lemna gibba (duck weed)	7-d ErC50 > 5.2 mg/L (initial measured, based on frond numbers) 7-d ErC50 > 0.229 mg/L (geomean measured, based on frond numbers)	Supporting study	Christ & Abedi (2002) amended by Mihan (2016)
Lemna minor (duckweed)	7-d ErC50 = 0.85 mg/L (initial measured, based on frond numbers) 7-d ErC50 = 0.40 mg/L (geomen measured, based on frond numbers)	Supporting study	Scheerbaum (2004) amended by Mihan (2016)
Lemna gibba (duck weed)	7-d ErC50 = 8.41 mg/L (initial measured, based on frond numbers)  7-d ErC50 = 0.113 mg/L (geomean measured, based on frond numbers)  7-d NOErC = 0.0107 mg/L (geomean measured, based on frond area)	Supporting study	Bruns (2012) amended by Mihan (2017)
Lemna gibba (duck weed)	7-d ErC50 >1.02 mg/L (initial measured)	Study is not considered valid since several TG validity criteria are not met.	Hughes & Williams (1993) amended by Smith (1999)
Lemna minor (duckweed)	7-d ErC50 = 0.85 mg/L (initial measured, based on frond numbers) 7-d ErC50 = 0.40 mg/L (geomen measured, based on frond numbers) 7-d ErC10 = 0.06 mg/L (geomen measured, based on frond numbers) 7-d ErC20 = 0.12 mg/L (geomen measured, based on frond numbers)	Endpoint and informations are included in summary of M-494089-01-1	Mihan (2017)

Key value for chemical safety assessment

EC50 for freshwater plants:

0.05 mg/L

EC10 or NOEC for freshwater plants:

0.002 mg/L