Mecoprop

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:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

Please see the read-across justification report in Section 13 of the dossier.

Reason / purpose for cross-reference:

read-across source

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

280 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Remarks on result:

other: 95 % confidence limits 199 - 418 µg/L

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

82.1 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95 % confidence limits 29.1 - 208 µg/L

Key result

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

69.4 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95 % confidence limits 23.1 - 180 µg/L

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Key result

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

31.7 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

31.7 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

31.7 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

31.7 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Yield

Effect conc.:

58.4 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Remarks on result:

other: 95 % confidence limits 44.3 - 76.2 µg/L

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

47 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Remarks on result:

other: 95 % confidence limits 15.9 - 107 µg/L

Duration:

14 d

Dose descriptor:

EC50

Effect conc.:

22.4 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Remarks on result:

other: 95 % confidence limits 11.0 - 36.6 µg/L

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

< 10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

< 10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

31.7 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

14 d

Dose descriptor:

LOEC

Effect conc.:

10 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Conclusions:

Under the conditions of the study the 14-day EyC50 was calculated to be 58.4, 22.4 and 47.0 μg test material/L for total shoot length, wet weight and dry weight, respectively.
The 14-day ErC50 was calculated to be 280, 82.1 and 69.4 μg test material/L for shoot length, wet weight and dry weight, respectively.
The 14-day NOEyC and the LOEyC were determined to be 10 and 31.7 μg test material/L for shoot length, < 10 and 10 μg test material/L for wet weight and dry weight, respectively.
The 14-day NOErC and the LOErC were determined to be 10 and 31.7 μg test material/L for shoot length and wet weight and 31.7 and 100 μg test material/L for dry weight, respectively.

Considering the very close structural similarity between the source and target substances (as justified in the read-across report that is attached to section 13 of the dossier), results from the study performed with mecoprop-p can be extrapolated to mecoprop.

Executive summary:

The toxicity of the test material to the aquatic plant Myriophyllum spicatum was assessed according to OECD Test Guideline 239 and in compliance with GLP.

Plants of were exposed in a static test to various concentrations of the test material under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 14 days.

This study encompassed 6 treatment groups (5 dose rates of the test material and a control) with five replicates per test concentration and ten replicates for the control.

After a pre-rooting phase of 7 days, one plant per replicate was incubated for 14 days under static conditions. The shoot length was determined at test start and day 14. Sub-lethal parameters were assessed at test start, once during the test (day 8) and at test end. At test end fresh and dry weight of each replicate was determined.

The samples collected at start and after 14 days were analysed via HPLC-MS/MS method.

Yield and growth rate based on main shoot length, wet and dry weight

At the start of the test 109 % of the nominal test concentration was found (average of all test concentrations). After 14 days test duration, 94 % of the nominal value was determined (average of all test concentrations). During the test the plants were exposed to a mean of 102 % of nominal. Therefore, all reported results refer to nominal concentrations.

Under the conditions of the study the 14-day EyC50 was calculated to be 58.4, 22.4 and 47.0 μg test material/L for total shoot length, wet weight and dry weight, respectively.

The 14-day ErC50 was calculated to be 280, 82.1 and 69.4 μg test material/L for shoot length, wet weight and dry weight, respectively.

The 14-day NOEyC and the LOEyC were determined to be 10 and 31.7 μg test material/L for shoot length, < 10 and 10 μg test material/L for wet weight and dry weight, respectively.

The 14-day NOErC and the LOErC were determined to be 10 and 31.7 μg test material/L for shoot length and wet weight and 31.7 and 100 μg test material/L for dry weight, respectively.

 

 

Findings from the study conducted with the read-across substance are viewed as representing a 'worst case' scenario bearing in mind it is information on the read-across substance that is driving the environmental classification of the registered substance. Hence relying on information on the read-across substance is viewed as representing a conservative approach to risk assessment of the registered substance.

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please see the read-across justification report in Section 13 of the dossier.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Growth

Effect conc.:

26.9 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Growth

Effect conc.:

53.3 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Growth

Effect conc.:

> 96.1 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: No effect > 50 % could be observed, therefore the EC50 was estimated to be estimated to be based on active ingredient content.

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Yield

Effect conc.:

9.41 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Yield

Effect conc.:

12 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

14 d

Dose descriptor:

EC50

Remarks:

Yield

Effect conc.:

> 96.1 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Remarks on result:

other: No effect > 50 % could be observed, therefore the EC50 was estimated to be estimated to be based on active ingredient content.

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.971 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

shoot length

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

0.971 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

96.1 µg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Conclusions:

Under the conditions of the study there was no effect > 50 % observed for the ErC50 and EyC50 for biomass dry weight, therefore the EC50 was estimated to be > 96.1 μg a.i./L.
The 14 day ErC50 was 26.9 μg/L, 53.5 μg/L and > 0.96.1 μg/L based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.
The 14 day EyC50 was 9.41 μg/L, 12.0 μg/L and > 96.1 μg/L, based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.
The 14 day NOEC was 0.971 μg/L for shoot length and biomass (fresh weight) and 96.1 μg/L based on biomass (dry weight).

Considering the very close structural similarity between the source and target substances (as justified in the read-across report that is attached to section 13 of the dossier), results from the study performed with mecoprop-p can be extrapolated to mecoprop.

Executive summary:

The toxicity of the test material to aquatic plants was assessed according to OECD Draft Guideline: Water-Sediment Myriophyllum sp Toxicity Test based on Draft AMRAP Method: Growth Inhibition Test for the Rooted Aquatic Macrophyte, Myriophyllum sp. Submitted to OECD for Evaluation, 22 July 2013 and in compliance with GLP.

Five replicates per test material concentration and ten replicates for the control were used. The duration of the test was 14 days. The test was performed under static test conditions. The nominal concentrations of the test material during the test were 1.91, 6.10, 19.5, 62.5 and 200 μg/L and control. This is equivalent to 0.917, 2.93, 9.37, 30.0 and 96.1 μg/L active ingredient. The test material was spiked to the water.

Test material concentrations in the definitive test were verified by analysis of the active ingredient at all concentration levels by analysing the overlying water at test start and test end and wet sediment at test termination on day 14.

On day 14 plants were harvested from each treatment group for assessment of shoot length, plant fresh weight, plant dry weight and number and length of side shoots. Additionally, the main shoot length was measured by use of a ruler on days 0, 7 and 14 during the test.

Endpoints reported are the EC50 for yield (EyC50) and growth rate (ErC50) based on the increase in total shoot length and biomass respectively after 14 days of exposure. The NOEC and LOEC for yield and growth rate were also determined. Temperature, pH and oxygen saturation [%] of the test solutions, measured after 0, 7 and 14 days, are reported.

The measured concentration of the test material based on the active ingredient content in the test vessels at test start ranged between 102 and 111 % of nominal in the overlaying water. The mean measured content for all concentrations at test start was 107 % of nominal for the active ingredient. After 14 days mean active ingredient concentrations in the overlaying water were below 95 % of nominal. As the mean contents of active ingredient were between 80 and 120 % of nominal at test start all toxicological endpoints were evaluated using nominal concentrations of the test material.

In the sediment amounts above the LOQ were only detected at the two highest concentration levels of 62.5 and 200 μg/L test material. The measured content in the sediment at day 14 was 7 % of nominal.

Since the guideline allows a mean coefficient of variation in the control cultures of 35 % EC20 and EC10 values should be treated with caution. It is likely that an increase or decrease of 10 - 20 % is disproportionately affected by the control variability. Consequently, statistical extrapolation of values which are below the lowest test concentration level or estimated from a flat dose response are likely to be unrealistic due to the natural variation between single plants. Total shoot length was found to be more sensitive than biomass (fresh and dry weight) for the EC50.

Under the conditions of the study there was no effect > 50 % observed for the ErC50 and EyC50 for biomass dry weight, therefore the EC50 was estimated to be > 96.1 μg a.i./L.

The 14-day ErC50 was 26.9 μg/L, 53.5 μg/L and > 0.96.1 μg/L based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14-day EyC50 was 9.41 μg/L, 12.0 μg/L and > 96.1 μg/L, based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14-day NOEC was 0.971 μg/L for shoot length and biomass (fresh weight) and 96.1 μg/L based on biomass (dry weight).

 

 

Findings from the study conducted with the read-across substance are viewed as representing a 'worst case' scenario bearing in mind it is information on the read-across substance that is driving the environmental classification of the registered substance. Hence relying on information on the read-across substance is viewed as representing a conservative approach to risk assessment of the registered substance.

Description of key information

Key study: Gonsior (2015) - Read across (MCPP-P)

Under the conditions of the study there was no effect > 50 % observed for the ErC50 and  EyC50 for biomass dry weight, therefore the EC50 was estimated to be > 96.1 μg a.i./L.

The 14 day ErC50 was 26.9 μg/L, 53.5 μg/L and > 96.1 μg/L based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14 day EyC50 was 9.41 μg/L, 12.0 μg/L and > 96.1 μg/L, based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14 day NOEC was 0.971 μg/L for shoot length and biomass (fresh weight) and 96.1 μg/L based on biomass (dry weight).

 

Supporting study: Seeland-Fremer & Mosch (2015) - Read across (MCPP-P)

Under the conditions of the study the 14-day EyC50 was calculated to be 58.4, 22.4 and 47.0 μg test material/L for total shoot length, wet weight and dry weight, respectively.

The 14-day ErC50 was calculated to be 280, 82.1 and 69.4 μg test material/L for shoot length, wet weight and dry weight, respectively.

The 14-day NOEyC and the LOEyC were determined to be 10 and 31.7 μg test material/L for shoot length, < 10 and 10 μg test material/L for wet weight and dry weight, respectively.

The 14-day NOErC and the LOErC were determined to be 10 and 31.7 μg test material/L for shoot length and wet weight and 31.7 and 100 μg test material/L for dry weight, respectively.

Key value for chemical safety assessment

EC50 for freshwater plants:

9.41 µg/L

EC10 or NOEC for freshwater plants:

0.971 µg/L

Additional information

Key study: Gonsior (2015) - Read across (MCPP-P)

The toxicity of the test material to aquatic plants was assessed according to OECD Draft Guideline: Water-Sediment Myriophyllum sp Toxicity Test based on Draft AMRAP Method: Growth Inhibition Test for the Rooted Aquatic Macrophyte, Myriophyllum sp. Submitted to OECD for Evaluation, 22 July 2013 and in compliance with GLP. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Five replicates per test material concentration and ten replicates for the control were used. The duration of the test was 14 days. The test was performed under static test conditions. The nominal concentrations of the test material during the test were 1.91, 6.10, 19.5, 62.5 and 200 μg/L and control. This is equivalent to 0.917, 2.93, 9.37, 30.0 and 96.1 μg/L active ingredient. The test material was spiked to the water.

Test material concentrations in the definitive test were verified by analysis of the active ingredient at all concentration levels by analysing the overlying water at test start and test end and wet sediment at test termination on day 14.

On day 14 plants were harvested from each treatment group for assessment of shoot length, plant fresh weight, plant dry weight and number and length of side shoots. Additionally, the main shoot length was measured by use of a ruler on days 0, 7 and 14 during the test.

Endpoints reported are the EC50 for yield (EyC50) and growth rate (ErC50) based on the increase in total shoot length and biomass respectively after 14 days of exposure. The NOEC and LOEC for yield and growth rate were also determined. Temperature, pH and oxygen saturation [%] of the test solutions, measured after 0, 7 and 14 days, are reported.

The measured concentration of the test material based on the active ingredient content in the test vessels at test start ranged between 102 and 111 % of nominal in the overlaying water. The mean measured content for all concentrations at test start was 107 % of nominal for the active ingredient. After 14 days mean active ingredient concentrations in the overlaying water were below 95 % of nominal. As the mean contents of active ingredient were between 80 and 120 % of nominal at test start all toxicological endpoints were evaluated using nominal concentrations of the test material.

In the sediment amounts above the LOQ were only detected at the two highest concentration levels of 62.5 and 200 μg/L test material. The measured content in the sediment at day 14 was 7 % of nominal.

Since the guideline allows a mean coefficient of variation in the control cultures of 35 % EC20 and EC10 values should be treated with caution. It is likely that an increase or decrease of 10 - 20 % is disproportionately affected by the control variability. Consequently, statistical extrapolation of values which are below the lowest test concentration level or estimated from a flat dose response are likely to be unrealistic due to the natural variation between single plants. Total shoot length was found to be more sensitive than biomass (fresh and dry weight) for the EC50.

Under the conditions of the study there was no effect > 50 % observed for the ErC50 and EyC50 for biomass dry weight, therefore the EC50 was estimated to be > 96.1 μg a.i./L.

The 14-day ErC50 was 26.9 μg/L, 53.5 μg/L and > 96.1 μg/L based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14-day EyC50 was 9.41 μg/L, 12.0 μg/L and > 96.1 μg/L, based on shoot length, biomass (fresh weight) and biomass (dry weight) respectively.

The 14-day NOEC was 0.971 μg/L for shoot length and biomass (fresh weight) and 96.1 μg/L based on biomass (dry weight).

 

Supporting study: Seeland-Fremer & Mosch (2015) - Read across (MCPP-P)

The toxicity of the test material to the aquatic plant Myriophyllum spicatum was assessed according to OECD Test Guideline 239 and in compliance with GLP. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Plants of were exposed in a static test to various concentrations of the test material under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 14 days.

This study encompassed 6 treatment groups (5 dose rates of the test material and a control) with five replicates per test concentration and ten replicates for the control.

After a pre-rooting phase of 7 days, one plant per replicate was incubated for 14 days under static conditions. The shoot length was determined at test start and day 14. Sublethal parameters were assessed at test start, once during the test (day 8) and at test end. At test end fresh and dry weight of each replicate was determined.

The samples collected at start and after 14 days were analysed via HPLC-MS/MS method.

Yield and growth rate based on main shoot length, wet and dry weight

At the start of the test 109% of the nominal test concentration was found (average of all test concentrations). After 14 days test duration, 94 % of the nominal value was determined (average of all test concentrations). During the test the plants were exposed to a mean of 102 % of nominal. Therefore, all reported results refer to nominal concentrations.

Under the conditions of the study the 14-day EyC50 was calculated to be 58.4, 22.4 and 47.0 μg test material/L for total shoot length, wet weight and dry weight, respectively.

The 14-day ErC50 was calculated to be 280, 82.1 and 69.4 μg test material/L for shoot length, wet weight and dry weight, respectively.

The 14-day NOEyC and the LOEyC were determined to be 10 and 31.7 μg test material/L for shoot length, < 10 and 10 μg test material/L for wet weight and dry weight, respectively.

The 14-day NOErC and the LOErC were determined to be 10 and 31.7 μg test material/L for shoot length and wet weight and 31.7 and 100 μg test material/L for dry weight, respectively.

 

 

 

Considering the very close structural similarity between the source and target substances (as justified in the read-across report that is attached to section 13 of the dossier), results from the study performed with mecoprop-p can be extrapolated to mecoprop.

 

Findings from the study conducted with the read-across substance are viewed as representing a 'worst case' scenario bearing in mind it is information on the read-across substance that is driving the environmental classification of the registered substance. Hence relying on information on the read-across substance is viewed as representing a conservative approach to risk assessment of the registered substance.