5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

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:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: U.S. EPA-FIFRA Pesticide Assessment Guidelines Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Substance ID: TSN 100097
- Name of substance: XDE-795
- Lot # DECO-97-152-1
- Purity: 97.4%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

acetone

Test organisms (species):

Anabaena flos-aquae

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Test temperature:

23.3 ± 0.04°C

pH:

7.1 to 7.7 (without alga)
8.7 to 9.1 (with alga)

Nominal and measured concentrations:

Nominal: 0.313, 0.625, 1.25, 2.5, 5.0, 10.0 mg/L, a media control group and an acetone solvent control group
Measured: 0.153, 0.265, 0.505, 0.956, 1.35, 0.722 mg/L

Reference substance (positive control):

no

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

> 1.35 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

120 h

Dose descriptor:

other: EC25

Effect conc.:

> 1.35 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

1.35 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: highest concentration tested

Validity criteria fulfilled:

yes

Conclusions:

120 hr EC50 (bluegreen algae): >1.35 mg/L (growth rate) (highest concentration tested)
120 hr NOEC (bluegreen algae): 1.35 mg/L (highest concentration tested)

Executive summary:

The effect of the test substance on the growth of freshwater bluegreen algae, Anabaena flos-aquae was assessed following U.S. EPA-FIFRA subdivision J, 123-2. Bluegreen algae were exposed to six target concentrations (0.313, 0.625, 1.25, 2.5, 5.0, 10.0 mg/L), a media control group and an acetone solvent control group (100 µL acetone/L media) for a duration of 120 hours (5 days). The mean measured concentrations were 0.153, 0.265, 0.505, 0.956, 1.35, 0.722 mg/L. Temperatures during the exposure period averaged 23.3 ± 0.04°C, light intensity averaged 2046 ± 160 lux, agitated daily.

The effects of the test substance on algal growth, relative to the combined controls, ranged from 13.7% inhibition of growth at 0.153 mg/L to 2.4% stimulation of growth at 0.265 mg/L.

The 5-day EC25 and EC50 values for algal growth were greater than 1.35 mg/L. The 5-day NOEC was 1.35 mg/L, the highest concentration tested.

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:

other: U.S. EPA-FIFRA Pesticide Assessment Guidelines, Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Substance ID: TSN 100097
- Name of substance: DE-795
- Lot: DECO-97-152-1
- Purity: 97.4%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

acetone

Test organisms (species):

Navicula pelliculosa

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

120 h

Test temperature:

23.6 ± 0.6°C

pH:

6.9-7.7 (without diatoms)
7.6-8.5 (with diatoms)

Nominal and measured concentrations:

Nominal: 0.0195, 0.039, 0.078, 0.156, 0.312, 0.625 mg/L, a media control group and an acetone control group
Mean measured: 0.0104, 0.0279, 0.0452, 0.115, 0.236, 0.391 mg/L

Reference substance (positive control):

no

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

28.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI: 3.91-213 µg/L

Duration:

120 h

Dose descriptor:

other: EC25

Effect conc.:

11.2 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI: 1.39-90.0 µg/L

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

28.7 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: inhibition of growth

Remarks on result:

other: 95% CI: 1.23-668 µg/L

Key result

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

10.4 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

120 h EC50 (freshwater diatom): 28.9 µg/L (growth rate)
120 h EbC50 (freshwater diatom): 28.7 µg/L (inhibition of growth)
120 h NOEC (freshwater diatom): 10.4 µg/L

Executive summary:

The effect of the test substance on the growth of a freshwater diatom, Navicula pelliculosa was assessed following U.S. EPA-FIFRA subdivision J, 123-2. Freshwater diatoms were exposed to six target concentrations (0.0195, 0.039, 0.078, 0.156, 0.312, 0.625 mg/L), a media control group and an acetone solvent control group (100 µL acetone/L media) for a duration of 120 hours (5 days). The mean measured concentrations were 0.0104, 0.0279, 0.0452, 0.115, 0.236, 0.391 mg/L. Temperatures during the exposure period averaged 23.6 ± 0.6°C, light intensity averaged 4363 ± 498 lux, agitated continuously at 75 rpm.

The effects of the test substance on diatom growth, relative to the combined controls, ranged from 0.4% inhibition of growth at 0.0104 mg/L to 99.7% inhibition growth at 0.236 mg/L.

The 5-day EC25 value (95% confidence intervals) for diatom growth was 11.2 µg/L (1.39-90.0 µg/L). The 5-day EC50 value (95% confidence intervals) for growth was 28.9 µg/L (3.91-213 µg/L). The regression equation for day 5 was total cell counts = 3695174-1618123 (Log Conc.), with an R² value of 0.682. The 5-day EbC50 value (95% confidence intervals) for inhibition of growth was 28.7 µg/L (1.23-668 µg/L). The regression equation for day 5 was percent inhibition of growth = -38.9-61.0 (Log Conc.), with an R² value of 0.696. The statistically derived 5-day NOEC was 10.4 µg/L.

Reference 3

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:

other: U.S. EPA-FIFRA Pesticide Assessment Guidelines, Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Substance ID: TSN 100097
- Name of substance: DE-795
- Lot: DECO-97-152-1
- Purity: 97.4%

Analytical monitoring:

yes

Vehicle:

yes

Remarks:

acetone

Test organisms (species):

Skeletonema costatum

Test type:

static

Water media type:

saltwater

Limit test:

no

Total exposure duration:

120 h

Test temperature:

20.5 ± 0.5°C

pH:

8.0-9.0 (without diatoms)
7.9-8.3 (with diatoms)

Nominal and measured concentrations:

Nominal: 0.078, 0.156, 0.313, 0.625, 1.25, 2.5 mg/L, a media control group and an acetone control group
Mean measured: 0.0303, 0.0423, 0.126, 0.196, 0.314, 0.577 mg/L

Reference substance (positive control):

no

Key result

Duration:

120 h

Dose descriptor:

EC50

Effect conc.:

0.106 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI: 0.030-0.360 mg/L

Duration:

120 h

Dose descriptor:

other: EC25

Effect conc.:

0.038 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI: 0.010-0.130 mg/L

Key result

Duration:

120 h

Dose descriptor:

NOEC

Effect conc.:

< 0.03 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

120 h EC50 (saltwater diatom): 0.106 mg/L (growth rate)
120 h NOEC (saltwater diatom): <0.0303 mg/L

Executive summary:

The effect of the test substance on the growth of a saltwater diatom, Skeletonema costatum was assessed following U.S. EPA-FIFRA subdivision J, 123-2. Saltwater diatoms were exposed to six target concentrations (0.078, 0.156, 0.313, 0.625, 1.25, 2.5 mg/L), a media control group and an acetone solvent control group (100 µL acetone/L media) for a duration of 120 hours (5 days). The mean measured concentrations were 0.0303, 0.0423, 0.126, 0.196, 0.314, 0.577 mg/L. Temperatures during the exposure period averaged 20.5 ± 0.5°C, light intensity averaged 4290 ± 581 lux, agitated continuously at 80 rpm.

The effects of the test substance on diatom growth, relative to the combined controls, ranged from 13.4% inhibition of growth at 0.0423 mg/L to 75.5% inhibition at 0.126 mg/L.

The 5-day EC25 value (95% confidence intervals) for diatom growth was 0.038 mg/L (0.010-0.130 mg/L). The 5-day EC50 value (95% confidence intervals) for growth was 0.106 mg/L (0.030-0.360 mg/L). The regression equation for day 5 was total cell counts = -35166-430580 (Log Conc.), with an R² value of 0.798. The 5-day NOEC was less than 0.0303 mg/L, the lowest level tested.

Reference 4

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: EEC Directive 67/548 Annex VIII, Part C (87/302/EEC)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: TSN 100010
Name of substance: XDE-795
Lot number: DECO-0325-7474
Purity: 98.7%

Analytical monitoring:

yes

Details on sampling:

Samples from each exposure test concentration were analyzed on day 0, 3 and 5 from each replicate test flask containing algae.

Vehicle:

yes

Remarks:

acetone

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Four separate dosing solutions were prepared to set the range of test concentrations; in order that the maximum solvent limit of 10 µL acetone/ 100 µL test solution would not be exceeded.
- Controls: There were two control groups: algal assay medium (AAM) with acetone and AAM without acetone.
- Evidence of undissolved material: It was suspected that the day 0 sample of the 496 µg/L stock solution contained residual undissolved test substance which resulted in an elevated measured concentration and was not included in the calculated average.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Green alga
- Strain: Pseudokirchneriella subcapitata
- Source: University of Texas, Austin, Texas
- Method of cultivation: Stock cultures of the organism are maintained aseptically by weekly transfer into sterile algal assay medium (AAM).

Test type:

static

Water media type:

freshwater

Total exposure duration:

5 d

Test temperature:

25.5 ± 0.04 ºC

pH:

7.4 - 7.7

Nominal and measured concentrations:

Nominal: 3.82, 7.64, 15.5, 31.0, 62.1, 124, 248 and 496 µg/L
Measured: 2.30, 4.63, 10.1, 14.9, 45.1, 86.6, 154 and 211 µg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL borosilicate Erlenmeyer flasks with Shimadzu closures containing 100 mL algal test medium
- Initial cells density: 3000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per solvent control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Continous agitation maintained at a constant rate of 100 rpm throughout the exposure
- Sterile test conditions: yes
- Photoperiod: Continous
- Light intensity and quality: 4305 ± 646 lux

EFFECT PARAMETERS MEASURED:
- The algal cell densities of the inoculum and test cultures were determined by electron particle counting using the Coulter Multisizer. Total cell counts were determined at approximately 24, 48, 72, 96, and 120 hours.

TEST CONCENTRATIONS
- Range finding study: A preliminary test was conducted with an objective to select treatment levels that result in both inhibition in algal growth and no inhibition or observable effect in growth. The test was carried out by exposing algae to four nominal concentrations of 9.97, 0.997, 0.0997, and 0.00997 mg/L including a control group; replicating each treatment twice. These test results indicated an inhibition of cell growth through 0.0997 mg/L and essentially no effect in growth at 0.00997 mg/L in comparison to the controls.
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

31.4 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% C. l.: 7.23-136.2 µg/L

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

57.5 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Percent inhibition

Remarks on result:

other: 95% C. l.: 7.79-424.6 µg/L

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4.63 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

5 d

Dose descriptor:

EC50

Effect conc.:

26.8 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% C. l.: 4.76-150.8 µg/L

Duration:

5 d

Dose descriptor:

EC50

Effect conc.:

27.8 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: Percent inhibition

Remarks on result:

other: 95% C. l.: 4.28-180.9 µg/L

Duration:

5 d

Dose descriptor:

NOEC

Effect conc.:

4.63 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Reported statistics and error estimates:

The NOEC’S given for algal growth were calculated using analysis of variance and the Dunnett's t test. The inhibition is a graphic interpretation of the data and the EC50and EC25 values were calculated based on the comparison of the areas under the growth curves between the control group and each exposure concentration.

Validity criteria fulfilled:

yes

Conclusions:

Day 3 and day 5 EC50 (algal growth): 31.4 and 26.8 µg/L, respectively
Day 3 and day 5 EC50 (percent inhibition): 57.5 and 27.8 µg/L, respectively
5 day NOEC (algal growth): 4.63 µg/L

Executive summary:

The test substance, was evaluated for its phytotoxicity to a freshwater green alga, Selenastrum capricornutum Printz over a five-day test period per the guideline OECD 201. Measured test concentrations, including two control groups (algal assay medium and algae; algal assay medium with acetone and algae), were set in a range from 2.30 to 211 µg/L. Treatment and control groups were set in triplicate with an initial cell density of 3000 cells/mL in each replicate.

The EC50 values and the 95% confidence intervals as well as the no observable effect concentrations, NOEC's, were determined on the endpoints, algal growth (total cell count/mL) and inhibition of growth (%) in comparison to the control group.

The day 3 and day 5 EC50 values and their 95% confidence intervals for algal growth were 31.4 (7.23-136.2) and 26.8 (4.76-150.8) µg/L, respectively; and 57.5 (7.79-424.6) and 27.8 (4.28-180.9) µg/L respectively, for percent inhibition. The day 5 NOEC for algal growth was 4.63 µg/L.

Reference 5

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 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: TSN 100097
Lot number: DECO-97-152-1
Purity: 97.3%

Analytical monitoring:

yes

Details on sampling:

At test initiation (0 hour), 24 hours and test termination (72 hours), a single sample was removed from each test concentration and the controls and analyzed for the test substance. Samples analyzed at 0 hour were removed from the test and control solutions prior to division into the replicate test vessels. Samples analyzed at 24 and 72 hours were removed from individually composited replicate solutions of the treatment levels and controls.

Vehicle:

yes

Remarks:

dimethylformamide

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A 460 μg a.i./mL primary stock solution was prepared prior to test initiation by placing 0.01182 g of the test substance (0.01150 g as active ingredient) in a 25-mL volumetric flask and bringing it to volume with dimethylformamide. Secondary stock solutions were prepared in dimethylformamide as dilutions of the primary stock solution. Nominal test concentrations were prepared by diluting 0.1 mL of Secondary stock solution with 1000 mL of sterile AAP medium.
- Controls: A solvent control solution was prepared by placing 0.10 mL of dimethylformamide in a 1000-mL flask and bringing it to volume with AAP medium. Additional untreated AAP medium was used for the control.
- Evidence of undissolved material: None; all test solutions were observed to be clear and colorless with no visible undissolved test substance.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Green alga
- Strain: Pseudokirchneriella subcapitata
- Source: University of Texas, Austin, Texas
- Age of inoculum (at test initiation): 4 days
- Method of cultivation: Stock cultures were grown in 250-mL glass flasks each containing 100 mL of AAP medium. The flasks were covered with stainless steel caps which permitted gas exchange.
The stock cultures were maintained within the following conditions: A shaking rate of 100 ± 10 rpm, a temperature of 23 ± 2°C and continuous illumination at the surface of the medium with an intensity range of 4400 to 5900 lux (420 to 550 footcandles). Lighting was supplied by fluorescent bulbs. Culture flasks were agitated continuously on an orbital shaker. Temperature was controlled using an environmental chamber.

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Test temperature:

23 to 24 ºC

pH:

7.1 to 7.7

Conductivity:

78 to 85 μS/cm

Nominal and measured concentrations:

Nominal: 2.9, 5.8, 12, 23 and 46 μg a.i./L
Time-weighted average concentrations: 2.0, 4.0, 9.0, 17 and 34 μg a.i./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250-mL Erlenmeyer flasks
- Type: All test vessels were fitted with stainless steel caps which permit gas exchange
- Initial cells density: 1.0 x 10e4 cells/mL.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per solvent control (replicates): 6

GROWTH MEDIUM
- Standard medium used: Yes

TEST MEDIUM
- The culture medium used was Algal Assay Procedure (AAP) medium prepared with sterile, deionized water. The AAP medium used to prepare the exposure solutions was formulated in the same manner as
the culture medium.
- Total organic carbon: 1.7 mg/L

OTHER TEST CONDITIONS
- The photosynthetically-active radiation (PAR) of the test area measured at test initiation ranged from 66 to 78 μE/m2/s.
- The shaking rate was maintained at a constant rate of 100 rpm throughout the exposure.
- Sterile test conditions: Yes
- Adjustment of pH: Adjusted to approximately pH 7.5 ± 0.1 with dilute hydrochloric acid or sodium hydroxide
- Photoperiod: Continous
- Light intensity and quality: 420 to 530 footcandles (4500 to 5700 lux)

EFFECT PARAMETERS MEASURED:
- At each subsequent 24-hour interval, cell counts were conducted on each replicate solution of the treatment levels and the controls using a hemacytometer and compound microscope. One sample was removed from each flask for counting. One or more hemacytometer fields, each 0.10 x 0.10 cm in surface area and 0.010-cm deep and containing 0.00010 mL of culture, were examined until at least 400 algal cells or four fields were counted. Observations of the health of the algal cells were also made and recorded at each 24-hour interval.

TEST CONCENTRATIONS
- Range finding study: A preliminary exposure was conducted at nominal concentrations of 0.046, 0.46, 4.6 and 46 μg a.i./L, a control and solvent (DMF) control. Two replicate exposure vessels were established for each concentration and the controls. Following 72 hours of exposure, cells exposed to all treatment levels tested and the controls were observed to be normal. Cell density in the control and solvent control averaged 39 and 63 x 10e4 cells/mL, respectively. Cell density in the 0.046, 0.46, 4.6 and 46 μg a.i./L treatment levels averaged 61, 51, 45 and 52 x 10e4 cells/mL, respectively.
- Results used to determine the conditions for the definitive study: Yes

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 34 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

act. ingr.

Basis for effect:

other: Yield and Average Growth Rate

Remarks on result:

other: Highest time-weighted average concentrations

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

34 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

act. ingr.

Basis for effect:

other: Yield and Average Growth Rate

Remarks on result:

other: Highest time-weighted average concentrations

Duration:

72 h

Dose descriptor:

other: EC10 and EC20

Effect conc.:

> 34 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

act. ingr.

Basis for effect:

other: Yield and Average Growth Rate

Remarks on result:

other: Highest time-weighted average concentrations

Details on results:

At test termination, cells exposed to all treatment levels tested and the controls were observed to be normal throughout the exposure period. The 72-hour cell density in the control and solvent control averaged 76.25 x and 59.00 x 10e4 cells/mL, respectively. Cell densities in the 2.0, 4.0, 9.0, 17 and 34 μg a.i./L treatment levels averaged 48.83, 63.25, 70.17, 58.25 and 55.25 x 10e4 cells/mL, respectively.

Reported statistics and error estimates:

The data were first checked for normality using Shapiro-Wilks' test and for homogeneity of variance using Bartlett's test. If the data sets passed the tests for homogeneity and normality, then Williams' test, Dunnett’s test or Bonferroni’s test was used to determine the NOEC. If the data did not pass the tests for homogeneity and normality, then Kruskal-Wallis' test was used to determine the NOEC. All statistical determinations were made at the 95% level of certainty, except in the case of Shapiro-Wilks' and Bartlett's tests, where the 99% level of certainty was applied. The EC values were calculated for yield (EyC10, EyC20 and EyC50 values) and average growth rate (ErC10, ErC20 and ErC50 values) by linear interpolation of response (percent reduction of yield and growth rate as compared with the solvent control) versus the time-weighted average concentration.

Validity criteria fulfilled:

yes

Conclusions:

72-Hour EC10, EC20 and EC50 (Yield and Average Growth Rate): > 34 μg a.i./L (Highest time-weighted average concentrations)
72-Hour NOEC (Yield and Average Growth Rate): 34 μg a.i./L

Executive summary:

The study was conducted to determine the effect of the test substance on the growth of the freshwater green alga Pseudokirchneriella subcapitata, according to the guideline OECD 201. Three replicate, sterile 250-mL Erlenmeyer flasks per treatment level, three for the control and six replicates for the solvent control were prepared. Following preparation of the test solutions and addition to the exposure flasks (100 mL per flask), a 0.298-mL inoculum of Pseudokirchneriella subcapitata cells, at a density of approximately 335 x 10e4 cells/mL, was aseptically introduced into each flask. This inoculum provided the required initial (0-hour) cell density of approximately 1.0 x 10e4 cells/mL. Test flasks were randomly placed on the shaking table at test initiation. At each subsequent 24-hour interval, cell counts were conducted on each replicate solution of the treatment levels and the controls using a hemacytometer and compound microscope.

At test termination, cells exposed to all treatment levels tested and the controls were observed to be normal throughout the exposure period. The 72-hour NOEC for yield and growth rate was determined to be 34 μg a.i./L. Since the highest concentration tested resulted in less than 10% reduction of yield and growth rate, the 72-hour EC10, EC20 and EC50 values were empirically estimated to be > 34 μg a.i./L, the highest time weighted average concentration tested.

Description of key information

72-hour E_rC₅₀ (Selenastrum capricornutum Printz): 31.4 µg/L; OECD 201; Reliability = 1

120-hour NOEC (Selenastrum capricornutum Printz): 4.63 µg/L; OECD 201; Reliability = 1

120-hour NOEC (freshwater diatom, Navicula pelliculosa): 10.4 µg/L; U.S. EPA-FIFRA Pesticide Assessment Guidelines, Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2; Reliability=1

120-hour NOEC (bluegreen algae, Anabaena flos-aquae): 1.35 mg/L (highest concentration tested); U.S. EPA-FIFRA Pesticide Assessment Guidelines, Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2; Reliability=1

120 h NOEC (saltwater diatom, Skeletonema costatum): <0.0303 mg/L; U.S. EPA-FIFRA Pesticide Assessment Guidelines, Subdivision J, Hazard Evaluation: Non-target Plants Guideline 123-2, Growth and Reproduction of Aquatic Plants, Tier 2; Reliability=1

Key value for chemical safety assessment

EC50 for freshwater algae:

31.4 µg/L

EC50 for marine water algae:

0.106 mg/L

EC10 or NOEC for freshwater algae:

4.63 µg/L

Additional information

Two algae toxicity tests were conducted in the freshwater species Pseudokirchneriella subcapitata and Selenastrum capricornutum. Acute 72 h E_rC₅₀ values were > 34 µg/L and 31.4 µg/L, respectively. The most sensitive species Selenastrum capricornutum has an acute 72h E_rC₅₀ less than 1 mg a.s./L. 

120-hour NOEC values were available in Selenastrum capricornutum, Navicula pelliculosa, Anabaena flos-aquae, and Skeletonema costatum. The most sensitive freshwater species was Selenastrum capricornutum, with a 120-hour NOEC value of 4.63 µg/L which is <0.1 mg/L (classification criteria limit for Category 1 for non-biodegradable substances). The 120-hour NOEC for the saltwater diatom, Skeletonema costatum, was also <0.1 mg/L.