3-fluoro-4'-(trans-4-propylcyclohexyl)-1,1'-biphenyl

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:

16 Oct 2017 - 22 May 2018

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 (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Concentrations of the test material were determined by treating aqueous samples with formic acid, then extracting with hexane. The extracts were diluted with hexane as required to bring the response within the calibration range. Samples were analysed by injection onto a gas chromatography / mass spectrometry (GC/MS) system.
At the start of the test (0 hours), ca 20 mL samples of freshly prepared test media were taken from control, 1.0, 3.2, 10, 32 and 100% saturated solution test media preparation flasks for chemical analysis.
At 72 hours, replicate test vessels at each treatment level were pooled and sampled. Samples (ca 20 mL) of each were taken for chemical analysis. At each sampling occasion, duplicate samples were taken. One sample for the initial analysis and one stored as “back-up”.

Vehicle:

no

Details on test solutions:

The dilution media used was EC medium as described in the OECD 201 Test Guideline.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

18 mg caCl 2H2O

Test temperature:

23-23.5 °C

pH:

7.6 - 8.9

Nominal and measured concentrations:

Nominal Measured values in mg/L
% 0 h 72 h geom. mean
saturated
solution
--------------------------------------------------------------
Control - - -
1.0 0.000308 0.000125** 0.000196
3.2 0.000599 0.00117 0.000837
10 0.00593* 0.000640 0.00195
32 0.00119 0.00032 0.000617
100 0.00350 0.00116 0.00202
--------------------------------------------------------------

- None found above limit of quantification (LOQ) of 0.000025 mg/L
* Mean of two results (0.00729 and 0.00456 mg/L)
** ½ LOQ value used as 72 hour result was found to be below the LOQ

Details on test conditions:

Preparation of Test Medium
The dilution media used was EC medium as described in the OECD 201 Test Guideline.
At the start of the definitive test, the 100% saturated solution test concentration was prepared by weighing 100.03 mg of test substance into a glass vial, the test substance was then added to 1000 mL of EC medium. This was then stirred for ca 24 hours, after stirring the media was filtered through 0.45 μm filters, discarding the first 100 mL filtered, the remaining concentrations were prepared using a serial dilution from the top concentration. A control treatment was prepared by adding EC medium only to the control vessels.

Test Vessel Preparation
The test vessels were sterile autoclaved glass 250 mL Erlenmeyer (conical) flasks, into which 100 mL of the appropriate control or test media was added. Sterile foam bungs were used to cover the top of the vessels.
Each test and control vessel was inoculated with sufficient Pseudokirchneriella subcapitata cells to achieve a starting algae cell concentration of 1 × 10^4 cells/mL. An additional inoculated vessel was prepared for the control and each test concentration for initial water quality analysis.

Test Vessel Sampling
At approximately 24-hour intervals after the start of the incubation period, pre-determined volumes of test media (1.0 mL at 24 hours and 0.5 mL at 48 and 72 hours) were removed from each incubated test vessel, and transferred to individually identified cell counting vials. The contents of each vial were diluted to a 10 mL final volume with an electrolyte solution. The cell density of the vial contents was then determined using a particle counter (Z2 Coulter Counter®).

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.002 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: nominal > 100 mg/L (above limit of water solubility)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.002 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Remarks on result:

other: nominal > 100 mg/L (above limit of water solubility)

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.002 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: nominal >= 100 mg/L (above limit of water solubility)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 0.002 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Yield

Remarks on result:

other: nominal >= 100 mg/L (above limit of water solubility)

Results with reference substance (positive control):

The 72-hour EC50 values for Yield, Area Under the Growth Curve and Growth Rate were determined to be 0.599, 0.604 and 0.875 mg/L, respectively. The 72-hour NOEC value for Yield, Area Under the Growth Curve and Growth Rate were determined to be 0.32, <0.1 and 0.32 mg/L, respectively.

Validity criteria fulfilled:

yes

Conclusions:

The results indicated that there was no toxicity at the limit of solubility of the test substance in the test media. Based on geometric mean measured concentrations, the 72-hour ErC50 and the 72-hour NOEC values were determined to be > 0.00202 mg/L and >= 0.00202 mg/L (nominal 100 mg/L), respectively.

Executive summary:

The objective of the study was to determine the effects of the test substance against algal growth by exposing the green alga, Pseudokirchneriella subcapitata, at the exponential growth phase to the test substance during a 72-hour test period.

The test was conducted in accordance with OECD Chemicals Testing Guideline No. 201. The definitive test was conducted at nominal test concentrations of 1.0, 3.2, 10, 32 and 100% saturated solution, a control group was also included. Six replicate vessels were prepared for the control and three replicate vessels were prepared for the 1.0, 3.2, 10, 32 and 100% saturated solution test groups.
Test vessels (250 mL conical flasks) were prepared containing 100 mL of the appropriate test or control medium. Each test vessel was inoculated with 1 × 10⁴algae cells/mL and incubated at 21 - 24°C (under 4440 - 8880 Lux light intensity) for 72 hours with cell counts at 24-hour intervals. Blank vessels were also prepared for the control and each test group, these vessels were not inoculated with algae and were for establishing back ground counts.
Measured test concentrations were determined from samples of test solution from treatment and control groups at the beginning of the test (new media) and the test end (old media).

Chemical analysis showed a declined in the test material concentration over the 72-hour test period. Therefore, results were based on geometric mean measured concentrations (based on guidance from study guideline).
The concentration inversion at the 10 and 32% saturated solution test groups was considered to be due to the low solubility of the compound causing difficulties with serial dilutions of the test media. The limited water solubility was also considered to have detrimental effects on the sensitivity of the analytical method. As the undiluted top concentration showed no effects this would also suggest that the dilution was causing the issues with achieved concentration. The media trials also confirmed this theory as they showed consistent achieved concentrations from one filtered sample with five analytical samples, whereas, the multiple preparations showed differing concentrations, this would suggest particulate may have been passing through the filter and ending up in the undiluted media, later being diluted into lower test level concentrations where it may have then been sampled and run in the analytical samples giving false concentration levels. These issues were not considered to impact on study integrity as there was no inhibition observed at the limit of water solubility or at the highest concentration tested in the test based on geometric mean measured concentrations in the test water.
Therefore, the inhibition observed at the lower test levels was considered to be due to the dilution problems mentioned above, as this inhibition was above the water solubility level which was considered to be 0.00350 mg/L (based on top test level 0 hour analytical result) it was not considered to impact on study integrity.
The 72-hour yield (EyCx) and growth rate (ErCx) toxicity values, with corresponding no observed effect concentration (NOEC) values, are presented below.

Yield: EyC50>0.00202 mg/L equivalent to nominal 100 mg/L
Growth Rate: EyC50>0.00202 mg/L equivalent to nominal 100 mg/L

The results indicated that there was no toxicity at the limit of solubility of the test substance in the test media.
All validity criteria were met therefore the test was considered valid

Based on geometric mean measured concentrations, the 72-hour ErC50 and the 72-hour NOEC values were determined to be > 0.00202 mg/L and >= 0.00202 mg/L (nominal 100 mg/L), respectively.

Description of key information

Based on geometric mean measured concentrations, the 72-hour ErC50 and the 72-hour NOEC (based on growth rate) values were determined to be > 0.00202 mg/L and >= 0.00202 mg/L (nominal 100 mg/L), respectively.