Triflumezopyrim

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

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:

other: U.S. Environmental Protection Agency Series 850 – Ecological Effects Test Guidelines OCSPP Guideline 850.4500 (2012)

Deviations:

yes

Remarks:

The study duration was 72 hours

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

- Common name: Freshwater green algae
- Strain: Pseudokirchneriella subcapitata
- Source: Wildlife International, Easton, Maryland.
- Algal cells used in this test were obtained from Wildlife International cultures that had been actively growing in culture medium for at least two weeks prior to test initiation. Algal cells for this study were taken from a culture that had been transferred to fresh medium four days prior to test initiation.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

Approximately 24, 48, and 72 hours

Test temperature:

22.4 to 23.1°C (measured in a container of water located adjacent to the test)

pH:

7.2 to 8.7 throughout the exposure period

Nominal and measured concentrations:

Nominal: 7.5, 15, 30, 60 and 120 mg a.s./L
Measured: 7.4, 15, 29, 59 and 118 mg a.s./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL Erlenmeyer flask containing 100 mL of test solution and plugged with foam stoppers
- Type of flow-through: static
- Renewal rate of test solution: No renewal
- Initial cells density: Approximately 10000 cells/mL
- Control end cells density: 10000 cells/mL
- No. of organisms per vessel: Approximately 10000 cells/mL
- No. of vessels per concentration: 4 replicates
- No. of vessels per control: 4 replicates


GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM
- Source/preparation of dilution water: Wildlife International
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: 24 hour
- Light intensity and quality: 5950 to 6480 lux

EFFECT PARAMETERS MEASURED :
Test concentrations were measured on day 0 and day 3 (72 hours) to verify stability of the test item. Cell counts were recorded for samples collected approximately 24, 48, and 72 hours after test initiation. Area under the growth curve (biomass), growth rate and yield were recorded and expressed as percent inhibition relative to the control replicates following exposure to test substance for 72 hours.

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 118 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: Biomass, growth rate and yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

59 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: Biomass, Growth rate and yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

118 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

other: Biomass, growth rate and yield

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): No abnormalities were observed
- Unusual cell shape: Not observed
- Colour differences: Not observed
- Adherence to test vessels: Not observed
- Aggregation of algal cells: Not observed
- Any stimulation of growth found in any treatment: Not observed

Reported statistics and error estimates:

Area under the growth curve, growth rate and yield data were evaluated for normality and homogeneity of variance (α = 0.01) using the Shapiro-Wilk’s and Levene’s tests, respectively. The data met all assumptions, therefore the treatment groups were compared to the control using ANOVA and Dunnett’s test (α = 0.05). The results of the statistical analyses, as well as an evaluation of the concentration-response pattern, were used to determine the NOEC and LOEC relative to each parameter at 72 hours.

Validity criteria fulfilled:

yes

Conclusions:

72 Hr-EC50 (P. subcapitata): > 118 mg a.s./L (Biomass, growth rate and yield)
72 Hr-NOEC (P. subcapitata): 59 mg a.s./L (Biomass, growth rate and yield)
72 Hr-LOEC (P. subcapitata): 118 mg a.s./L (Biomass, growth rate and yield)

Executive summary:

The study was conducted according to guidelines, OECD 201 and U.S EPA OCSPP 850.450 to determine the acute toxicity of test substance to Pseudokirchneriella subcapitata under static conditions in a 72-hour exposure test. The study was conducted with five concentrations of test substance, a blank (freshwater algal medium) control, and an abiotic (stability) control in an environmental chamber for three days at 23 ± 2°C. Four replicates were initiated for each test substance concentration and for the blank control. One test vessel containing no P. subcapitata was initiated for the abiotic control, which was included to demonstrate the stability of the test substance in freshwater algal medium under the test conditions without the presence of the test organism. Cell counts were taken from samples collected daily during the test. Cell density and the corresponding yields, areas under the growth curve and growth rates were determined.

Treatments consisted of five test substance concentrations of 7.5, 15, 30, 60 and 120 mg a.s./L, an untreated blank control and an abiotic (stability) control. Mean, measured concentrations of test substance were 7.4, 15, 29, 59 and 118 mg a.s./L. Recovery from the abiotic control at test termination was 99% of nominal, indicating that the test substance was stable over the course of the test. Therefore, results are based on mean, measured active substance concentrations.

At test conclusion, cell density increased in the blank control by at least a factor of 16 in three days, the mean coefficient of variation for section-by-section specific growth rates (Days 0-1, 1-2, and 2-3) in the control replicates did not exceed 35%, and the coefficient of variation for the average specific growth rates in the control replicates was less than 7%. The test therefore meets all validity criteria.

The ECx, NOEC and LOEC values for P. subcapitata were based on mean, measured concentrations of test substance for area under the growth curve (biomass), growth rate and yield. The 72-hour E_bC50, E_rC50 and E_yC50 values based on biomass, growth rate and yield, respectively, were all >118 mg a.s./L, based on the mean, measured concentration of test substance. The NOEC and LOEC for biomass, growth rate and yield were 59 and 118 mg a.s./L, respectively.

Description of key information

72 -hour EC50 (Pseudokirchneriella subcapitata, algae) > 118 mg/L; OECD 201; Reliability = 1

72 -hour NOEC (Pseudokirchneriella subcapitata, algae) = 59 mg/L; OECD 201; Reliability = 1

Key value for chemical safety assessment

EC50 for freshwater algae:

118 mg/L

EC10 or NOEC for freshwater algae:

59 mg/L

Additional information

An algae toxicity test was conducted in the freshwater species Pseudokirchneriella subcapitata.  The acute 72 h ErC50 value was >118 mg a.s./L and the 72 -hr NOEC value was 59 mg a.s./L.