Methomyl

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch 16RLMX99
Purity: 100.0%

Analytical monitoring:

yes

Details on sampling:

Water samples from the control and 100 mg/L test group at 0 and 72 hours for quantitative analysis. Duplicate samples were taken at each occasion and stored frozen (approximately -20°C) for further analysis.

Vehicle:

yes

Remarks:

water

Details on test solutions:

100 mg of test material was dissolved in culture medium and the volume adjusted to 500 mL to give a 200 mg/L stock solution. This stock solution was mixed with algal suspension (500 mL) to give the required concentration of 100 mg/L.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Centre for Algae and Protozoa (CCAP). Institute of Freshwater Ecology, Ferry House, Ambleside, Culbria
- Age of inoculum (at test initiation): not reported
- Method of cultivation: not reported

ACCLIMATION
- Acclimation period: not reported

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

24±1°C

pH:

Control: 7.4 at 0 hours; 9.8-9.9 at 72 hours. This increase is due to the large number of cells in the log phase of growth respiring oxygen and producing carbonates and bicarbonates as part of photosynthesis/respiration which in solution give rise to alkaline conditions. This is in excess of recommended limits in the test guidelines. This is considered to have had no adverse efect on the study or the results obtaned given that the growth of the control cultures exceeded the 16 fold enhancement factor given in the OECD guideline and that the cell density values obtained confirmed that log phase growth was maintained over the study period.

Nominal and measured concentrations:

Nominal: 0 and 100 mg/L
Measured: 0 and 94 mg/L

Details on test conditions:

Due to an oversight by the technician who prepared the culture medium for use in the definitive study, the culture medium was not sterilised by 0.2 µm filtration prior to use. This is considered to have had no adverse effect on the study given that the results of the study confirm that the culture medium used was of sufficient quality for use in the study.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 94 mg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 94 mg/L

Nominal / measured:

meas. (not specified)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

94 mg/L

Nominal / measured:

meas. (not specified)

Nominal concentration (mg/L)	Area under curve at 72 h	% Inhibition	Growth rate (0-72 h)0.078	% inhibition
Control	3.92 x10E7	-	0.081	-
100	3.65 x10E7	7		4

Validity criteria fulfilled:

yes

Conclusions:

72-hour ErC50 and EbC50 was > 100 mg/L
No Observed Effect Concentration was 100 mg/L. 

Executive summary:

A study was performed to assess the effect of the test material on the growth of the green algae, Pseudokirchneriella subcapitata, following OECD guideline 201 and Method C.3 of Commission Directive 92/769/EEC. Following a preliminary range-finding study, algae were exposed to an aqueous solution of the test material at a concentration of 100 mg/L (six replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24±1°C. Samples of algal populations were removed daily and cell concentrations determined for each control and treatment group, using a haemocytometer and light microscope.

The 72-hour ErC50 and EbC50 was > 100 mg/L and the corresponding No Observed Effect Concentration was 100 mg/L. 

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch 16RLMX99
Purity: 100.0%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

water

Test organisms (species):

Scenedesmus sp.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

24±1°C

pH:

7.5-8.3

Nominal and measured concentrations:

Nominal: 0 10, 18, 32, 56, and 100 mg/L
Measured: 0, 9.52, 17.9, 28.9, 53.2, and 96.3 at 0 hours
Measured: 0, 9.70, 18.2, 32.0, 54.1, and 99.4 at 72 hours

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Validity criteria fulfilled:

yes

Conclusions:

72-hour ErC50 and EbC50 was > 100 mg/L
No Observed Effect Concentration was 100 mg/L. 

Executive summary:

A study was performed to assess the effect of the test material on the growth of the green algae, Scenedesmus subspicatus strain CCAP 276/20 following OECD guideline 201 and Method C.3 of Commission Directive 92/769/EEC. Following a preliminary range-finding study, algae were exposed to an aqueous solution of the test material at a concentration of 0, 10, 18, 32, 56, and 100 mg/L (three replicate flasks) for 72 hours, under constant illumination and shaking at a temperature of 24±1°C. Samples of algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle counter.

The 72-hour ErC50 and EbC50 was > 100 mg/L and the corresponding No Observed Effect Concentration was 100 mg/L. 

Description of key information

Duration/Value Type	Species	Value	Guideline	Reliability
72-hr ErC50	Scenedesmus subspicatus	> 100 mg/L	OECD 201, EU Method C.3	1
72-hr NOEC	Scenedesmus subspicatus	100 mg/L	OECD 201, EU Method C.3	1
72-hr ErC50	Pseudokirchneriella subcapitata	> 100 mg/L	OECD 201, EU Method C.3	1
72-hr NOEC	Pseudokirchneriella subcapitata	100 mg/L	OECD 201, EU Method C.3	1

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

The 72-hr ErC50 in Scenedesmus subspicatus and Pseudokirchneriella subcapitata was > 100 mg/L. The 72-hr NOEC in these species was 100 mg/L (the highest concentration tested). These studies were conducted according to OECD 201 and EU Method C.3. An older study in Scenedesmus subspicatusf ound a 72-hr EbC50 of 60 mg/L. An EC50 for growth rate was not reported in this study.