2-chloro-N-[[[4-(trifluoromethoxy)phenyl]amino]carbonyl]benzamide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study initiated/completed: 9 October 1989 -13 October 1989.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

June 7, 1984

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Version / remarks:

November 15, 1989

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Sampling method: The stock culture of the green algal species employed is maintained under 16 hours of light per day and at 20 °C in an autoclaved nutrient solution. The stock cultures are transferred into fresh nutrient solution once a week. All nutrient solutions are prepared using deionized filter-sterilized water. The inoculation and transfer of algae suspensions is done under sterile conditions (sterile bench).

The pre-cultures are inoculated with 1*10^4 cells/ml. For the test, the algae from the exponentially-growing pre-culture are exposed to the various test concentrations 3 days later at an initial concentration of 1*10^4 cells/ml.
300 ml labelled (study number, series number, concentration) narrow-necked
Erlenmeyer flasks served as test containers. Details on test solutions are given.

For the evaluation, cell counts were performed indirectly by photometric
evaluation of extinction / turbidity. A sample of the test suspension was
filled into a 5 cm-cuvette and the wave-length was determined at 578 nm
with the aid of a 1 beam-photometer. (The photometer was adjusted to the corresponding dispersion without algae under the same test conditions).

This 2nd order polynom was evaluated using a series of 58 single counts of
cells under a microscope at a magnification of 400 diameters in the Thoma-Zeiss counting chamber and the corresponding extinction with Scenedesnius
subspicatus under the test conditions. The deviations for these values are
± 0.00019 resp. ± 0.00000053. With the first constant, there are minimal
differences to the corresponding constant of the 1st order polynom.

Additionally, a sample of each flask was examined under a microscope at a
magnification of 400 diameters to detect possible cell alteration (as unusual cell size) that might influence the extinction. The cell counts are performed with the help of the photometer only if there are no alterations that might influence extinction. Temperatures and pH values of the test suspensions were determined with the aid of electronic measurement equipment.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

For the test, 26 mg of triflumuron were weighed ad 100 mL Acetone and stirred for 5 minutes on a magnetic stirrer. The final test concentrations were prepared from this stock solution by adding the appropriate amounts of deionized water. The highest concentration of Acetone resulted in 0.1 mL Acetone/L (at the test concentration 25 µg/L). The test concentrations were chosen according to the water solubility of triflumuron (25 µg/L).

Test organisms (species):

other: Scenedesmus subspicatus

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test temperature:

20°C

pH:

8.26

Nominal and measured concentrations:

The nominal concentrations were 1, 10 and 25 µg/L. According to the water solubility of 25 µg/L, higher concentrations could not be tested. For the highest test concentration without any biological effect the measured concentration level was 87.4% of the expected nominal concentration. This is in good agreement with the nominal concentration.

Details on test conditions:

The Erlenmeyer flasks were exposed in an incubator at 23 ± 2 °C and 8000
lux continuous light (spherical, +. 20 %, measured with a three-dimensional
quantum radiometer photometer). Illumination was provided by 2 x 4
fluorescent lamps (Osram L 140 W/20 Sa) that were attached on the sides of
the incubator. Moreover, the inner walls of the incubator were covered with
reflective material, so that a uniform illumination at all points of the
interior was assured. The illumination intensity of the lamps was adjusted
by means of two dimmers to maintain it at the level required by the
guideline. By intermittent turning of the support frame in the incubator
(6.5 thrusts per revolution, 3 revolutions per minute), sedimentation of
the algal cells was prevented and the light exposure of the individual
flasks was made even more uniform.

Reference substance (positive control):

yes

Remarks:

K2Cr2O7

Key result

Duration:

96 h

Dose descriptor:

other: ErC50

Effect conc.:

> 25 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: same at 72h

Key result

Duration:

96 h

Dose descriptor:

other: EbC50

Effect conc.:

> 25 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: same at 72h

Key result

Duration:

96 h

Dose descriptor:

LOEC

Effect conc.:

> 25 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: toxicity

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 25 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: toxicity

Details on results:

No abnormalities, e.g. morphological changes, were observed. The growth in the control containers after 3 days shows a rate of reproduction that is greater than a factor of 16 and thus fulfills the quality of the ISO and/or OECD guideline.

As the physical/chemical measurements showed, the nature of the 10× nutrient solution also corresponds to the required nominal values. The pH-values increased slightly during the tests according to the increasing number of algal cells (lack of CO2). According to the guidelines specified, the control pH did not vary more than 1.5 units.

Results with reference substance (positive control):

Test was performed on August 7, 1989, under the same conditions using the reference standard K2Cr2O7 reagent grade in accordance with GLP regulations (test concentrations 0.18, 0.32, 0.56, 1.0 and 1.8 mg/L) (Report HBF/A1 70 of August 31, 1989 GLP study number: E 323 0335-9). In this test, the 72-hours EC50 determined for the growth of the biomass (EbC50), 0.58 mg/L, agrees well with the results of a collaborative study in which the test results ranged from 0.20 - 0.75 mg/L. The 72-hours EC50 determined for the algal growth rate (ErC50) , 1.09 mg/L falls also in the corresponding range of the collaborative study (0.60 - 1.03 mg/L).

Validity criteria fulfilled:

yes

Conclusions:

In accordance with GLP-regulations, tri-flumuron was tested for its toxicity to green algae in accordance with the ISO-Buideline ISOS 8692 : 1989 (E) (Water quality - Fresh water algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum) dated June 25, 1987 and OECD-Guideline No. 201 "OECD Guideline for Testing of Chemicals", "Alga, Growth Inhibition Test" dated June 7, 1984. The green algae (Scenedesmus subspicatus) were exposed under static sterile conditions. After 24, 48, 72 and 96 hours, the cell counts were determined. The nominal concentrations were 1, 10 and 25 µg/L. According to the water solubility of 25 µg/L, higher concentrations could not be tested. For the highest test concentration without any biological effect (25 µg/L, see Table 1) the measured concentration level was 87.4% of the expected nominal concentration. This is in good agreement with the nominal concentration. >25 µg/L was the result for EbC50, ErC50 and LOEC. The NOEC was determined to be = 25 µg/L.

Description of key information

Triflumuron was tested for its toxicity to green algae (Scenedesmus subspicatus)  under static sterile conditions. The nominal concentrations were 1, 10 and 25 µg/L, limited by the water solubility of the test item. For the highest test concentration without any biological effect (25 µg/L) the measured concentration level was 87.4% of the expected nominal concentration.

EbC50 >25 µg/L 

ErC50 >25 µg/L

LOEC >25 µg/L

NOEC = 25 µg/L.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

25 µg/L