2-[4-(4-Alkoxyphenyl)-(pyridin-2-yl)-heteromonocyclyl]phenol

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

Study period:

Study initiation date - 27 May 2021; Experiment start date - 28 May 2021; Experiment end date - 10 June 2021; Study completion date - 02 July 2021.

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

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Test Item: FAT 75637/B TE
Physical appearance: Light yellow powder
Purity as per Certificate of Analysis: 99.4 % all organic constituents; 95.0 % main constituent
Batch No: AT-0063765400
pH: 6.7 (aq. susp. of 2 % (w/w) at room temperature)
Manufactured date: 21st April 2020
Expiry date: 27th May 2025
Storage conditions: Ambient (+15 to +25 ºC)

Analytical monitoring:

yes

Details on sampling:

The recovery of the test item in the test medium was assessed at room temperature at nominal concentrations of 1.012 mg/L and 151.000 mg/L, using a validated analytical method. All the test concentrations along with the negative control were analyzed for the test item concentration at the beginning, at 24 hour, at 48 hour and at the end of the test. For the analysis, duplicate set of composite samples were drawn from the prepared test concentrations and from the negative control. The criteria for acceptance of analysis results of test concentration were 80 to 120 % of nominal concentration with ≤20 % RSD of analyzed concentration.

Vehicle:

no

Details on test solutions:

Test item stock of 1 mg/mL was prepared by grinding 500 mg test item in test medium and made up to 500 mL in a volumetric flask using test medium and sonicated for 30 minutes. Control (G1) was prepared by adding 3.2 mL algal suspension to achieve initial cell density of 1x10E4 cells/mL and made up to 1 L in a volumetric flask using test medium. To prepare test concentrations of 3.125 (G2), 6.25 (G3), 12.5 (G4), 25 (G5) and 50 (G6) mg/L, 3.125, 6.25, 12.5, 25 and 50 mL of test item stock was mixed with test medium, 3.2 mL algal suspension was added to achieve initial cell density of 1x10E4 cells/mL and made up to 1 L in a volumetric flask using test medium separately. 150 mL of prepared negative control was dispensed into 6 test containers and 150 mL of each test item concentration was dispensed separately into 3 test containers.

Test organisms (species):

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

Details on test organisms:

Source: American Type Culture Collection, P.O. Box 1549, Manassas, VA 20108, USA

Culture Maintenance:
Algal cells were maintained at the test facility through sub-culturing once in 5 to 10 days from the continuous culture into fresh medium in a conical flask. These conical flasks were incubated between 21 and 25 °C (± 2 °C) under a white fluorescent continuous illumination of 8000 ± 1600 Lux.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.1 to 22.6 °C

pH:

8.12- 8.19

Nominal and measured concentrations:

Definitive test: 0, 3.125, 6.25, 12.5, 25, 50 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: Conical flask
- Type: closed
- Material, size: Glass, 250 mL,
- Initial cells density: 1 x 10E4 /mL
- No. of vessels per concentration (replicates): Three
- No. of vessels per control (replicates): Six

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: Continuous illumination
- Light intensity and quality: 8000 ± 1600 Lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: The algal biomass in each flask was determined at 24, 48 and 72 hours after the start of the test using a haemocytometer

TEST CONCENTRATIONS
- Range finding study: A range finding test was conducted to select the test concentrations for the definitive test with a negative control and test item concentrations at 0.01, 0.1, 1, 10 and 50 mg/L. Each group had single replicate.
- Results used to determine the conditions for the definitive study: The test item exhibited 0, 0, 0, 19.37 and 25.05 % inhibition at the tested concentrations of 0.01, 0.1, 1, 10 and 50 mg/L respectively at 72 h.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 50 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Test Item Solubility

FAT 75637/B was tested for its solubility in the test medium and formed semi-transparent cream coloured formulation with visible solid particles in test medium at 50 mg/L.

Definitive test result:

At the end of the test (72 hours), the cell biomass in the test item solutions decreased with the increase in test concentration. At test concentration of 3.125, 6.25, 12.5, 25 and 50 mg/L, the observed inhibition in the growth rate of algal biomass was 0, 0, 20.06, 21.54 and 24.82 %; and the percent yield inhibition was 0, 0, 59.18, 61.82 and 67.11 %, respectively when compared to that of the negative control at the end of the 72 hour test period. Observed cells were found morphologically normal in all the tested concentrations at the end of test. The EC10 and EC20 values for growth were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations. The EC50 value for growth rate was higher than 50 mg test item/L based on the nominal concentrations. The EC10, EC20 and EC50 values for yield were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations.

VALIDITY OF TEST

There was an increase in cell concentration of the negative control culture by a factor of 78.79, which is more than the required factor limit of at least 16 at the end of the test. The mean coefficient of variation for section-by-section specific growth rates in the negative control cultures during the test was 27.64 %, which is within the required limit of 35 %. The coefficient of variation of average growth rate between replicate cultures of negative control was 0.27 , which is within the required limit of 7 %.

Analysis of Test Concentrations

The test item was recoverable at nominal concentrations of 1.012 mg/L and 151.000 mg/L in the test medium. The active ingredient concentration analysis in all test concentrations showed that the recovery with nominal concentration for was in the range of 84.309 to 105.025 % (RSD was 2.273 to 13.560%) at the start (0 hour), 97.185 to 114.299 % (RSD was 2.491 to 12.480 %) at 24 hour, 85.643 to 111.003 % (RSD was 0.745 to 7.417 %) at 48 hour and 84.331 to 107.443 % (RSD was 2.780 to 16.869 %) at the end of the test (72 hour).

Validity criteria fulfilled:

yes

Conclusions:

The EC50 value for growth rate was higher than 50 mg test item/L based on the nominal concentrations.

Executive summary:

The effect of FAT 75637/B was tested on the growth of freshwater unicellular green alga Raphidocelis subcapitata for 72 hours. This study was conducted according to OECD test guideline 201 in a GLP certified laboratory. The alga was exposed to the test item at the test concentrations 3.125, 6.25, 12.5, 25 and 50 mg/L along with a negative control. Six replicates were maintained for the negative control and three replicates for the test concentrations. The initial cell density of algal cells at the start of exposure was 1 x 10E4/mL. The cell growth was measured at 24, 48 and 72 hours after the initiation of the test using a haemocytometer (microscopic observation). At test concentration of 3.125, 6.25, 12.5, 25 and 50 mg/L, the observed inhibition in the growth rate of algal biomass was 0, 0, 20.06, 21.54 and 24.82 %; and the percent yield inhibition was 0, 0, 59.18, 61.82 and 67.11 %, respectively, when compared to that of the negative control at the end of the 72 hour test period. Observed cells were found morphologically normal in all the tested concentrations at the end of test. The test item was recoverable at nominal concentrations of 1.012 mg/L and 151.000 mg/L in the test medium. The active ingredient concentration analysis in all test concentrations showed that the recovery with nominal concentration was in the range of 84.309 to 105.025 % (RSD was 2.273 to 13.560 %) at the start (0 hour), 97.185 to 114.299 % (RSD was 2.491 to 12.480 %) at 24 hour, 85.643 to 111.003 % (RSD was 0.745 to 7.417 %) at 48 hour and 84.331 to 107.443 % (RSD was 2.780 to 16.869 %) at the end of the test (72 hour). The end point values for growth rate and yield 72 hours are presented below based on nominal concentration. The EC10 and EC20 values for growth were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations. The EC50 value for growth rate was higher than 50 mg test item/L based on the nominal concentrations. The EC10, EC20 and EC50 values for yield were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations.

Description of key information

The EC50 value for growth rate was higher than 50 mg test item/L based on the nominal concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

50 mg/L

EC10 or NOEC for freshwater algae:

6.25 mg/L

Additional information

The effect of FAT 75637/B was tested on the growth of freshwater unicellular green alga Raphidocelis subcapitata for 72 hours. This study was conducted according to OECD test guideline 201 in a GLP-certified laboratory. The algal cells were exposed to the test item at the test concentrations 3.125, 6.25, 12.5, 25 and 50 mg/L along with a negative control. Six replicates were maintained for the negative control and three replicates for the test concentrations. The initial cell density of algal cells at the start of exposure was 1 x 10E4/mL. The cell growth was measured at 24, 48 and 72 hours after the initiation of the test using a haemocytometer (microscopic observation). At test concentration of 3.125, 6.25, 12.5, 25 and 50 mg/L, the observed inhibition in the growth rate of algal biomass was 0, 0, 20.06, 21.54 and 24.82 %; and the percent yield inhibition was 0, 0, 59.18, 61.82 and 67.11 %, respectively when compared to that of the negative control at the end of the 72 hour test period. Observed cells were found morphologically normal in all the tested concentrations at the end of test. The test item was recoverable at nominal concentrations of 1.012 mg/L and 151.000 mg/L in the test medium. The active ingredient concentration analysis in all test concentrations showed that the recovery with nominal concentration was in the range of 84.309 to 105.025 % (RSD was 2.273 to 13.560 %) at the start (0 hour), 97.185 to 114.299 % (RSD was 2.491 to 12.480 %) at 24 hour, 85.643 to 111.003 % (RSD was 0.745 to 7.417 %) at 48 hour and 84.331 to 107.443 % (RSD was 2.780 to 16.869 %) at the end of the test (72 hour). The endpoint values for growth rate and yield 72 hours are presented below based on nominal concentration. The EC10 and EC20 values for growth were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations. The EC50 value for growth rate was higher than 50 mg test item/L based on the nominal concentrations. The EC10, EC20 and EC50 values for yield were between 6.25 mg/L (5.94 mg a.i./L) and 12.5 mg/L (11.88 mg a.i./L) based on the nominal concentrations.