Fenuron

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:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Principles of method if other than guideline:

aeration with 95% air 5% CO2; but cultures were in exponential phase at least up to 65 hours, light intensity 4300 lx., exact exposure duration not provided "between 48 hr and 72 hr" for the different algae species) Extinction at 550 nm measured. Experiments were performed twice.

GLP compliance:

no

Analytical monitoring:

not specified

Test organisms (species):

Chlorella pyrenoidosa

Details on test organisms:

TEST ORGANISM
- Common name: Chlorella pyrenoidosa
- Strain: 211/8h
- Source (laboratory, culture collection): C.C.A.P. Culture Collection of Algae and Protozoa, Cambridge, UK

Test type:

static

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

"between 48 hr and 72 hr", not specified further

Test temperature:

25.0 +/- 0.1°C

Nominal and measured concentrations:

0 (control), 0.1, 0.25, 0.5, 0.75, 1.0, 2.0, 5.0 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: test tubes 150 x 25 mm, each fitted with an aeration tube (250x 3.5 mm) held in place by a cotton wool or rubber bung.
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 20.4 mL
- Aeration: yes 95% air, 5% CO2
- Initial cells density: "20 mL medium were inoculated with 0.4 mL standardized cell suspension"
- Control end cells density: not provided for the individual tests, but the publication cobntains a statement that "Chlorella grew to 0.9 mg/mLdry weight in 65 hr"
- No. of vessels per concentration (replicates): not provided, but the experiment was performed twice
- No. of vessels per control (replicates): not provided, but the experiment was performed twice

GROWTH MEDIUM
- Standard medium used: yes, stanard medium at the time when the publication was prepared (Samejima & Myers, 1958)


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: 4300 lx fluorescent tubes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:optical density at 550 nm
- Chlorophyll measurement: no
- Other: the publication contains a statement that the optical density at 550 nm correlates well with the dry weight and extracted pigments

Reference substance (positive control):

no

Dose descriptor:

EC50

Effect conc.:

0.53 mg/L

Basis for effect:

biomass

Remarks on result:

other: no further information provided

Details on results:

- Exponential growth in the control (for algal test): not determined for the that test, but there was a statement that the cultures are in exponentional growth for 65 hours.
- Effect concentrations exceeding solubility of substance in test medium: no

Concentration [mg/L]	% of control growth
0 (Control)	100
0.1	100.2
0.25	81.5
0.5	51.5
0.75	33.6
1	21.9
2	9.9
5	8.6
EC50	0.53 mg/L

Conclusions:

about 3 day EC50 Chlorella pyrenoidasa: 0.53 mg/L

Executive summary:

WRIGHT (1972) reported a 50% inhibition of the growth of Chlorella pyrenoidasa by 0.53 ppm of fenuron when exposed between 48 and 72 hours. Aeration was performed with 95% air and 5% CO2 light intensity was 4300 lux. The growth of the cultures was determined by measureing the optical density at 550 nm.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Principles of method if other than guideline:

- Principle of test: According to ASTM 1980
static test, exposure for 240 hours, 12 light/12 h darkness, growth analysed (OD 525 nm), EC50 calcualted
- Parameters analysed / observed: growth based on increase of optical density (525 nm) after 10 days exposure

The results from Walsh (1972) were published before modern guidelines were available. The EPA publication (Mayer 1987) contains a statement that the data base listed in the EPA publication was reviewed and only results considered to be acceptable were reported in the EPA-List. The results from Walsh (1972) were reported in that EPA-document.

GLP compliance:

no

Analytical monitoring:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: In Walsh (1972) the preoaration of the stock solution is not described. According to Mayer (1987) the stock solutions were prepared with either acetone, ethanol, polyethylene glycol, triethylene glycol or water as carrier/solvent. Solvent concentrations did not exceed 1.0 mL/L in the exposure containers. Sine the herbicides tested by Walsh are highly water soluble, it is not unlikely that the stock solutions were prepared in water. Nevertheless, it has to be pointed out that It is not specified how the test solutions for the test reported here have been prepared.

Test organisms (species):

other: Isochrysis galbana

Details on test organisms:

TEST ORGANISM
- Common name: Isochrysis galbana
- Source (laboratory, culture collection): The algae used for the experiments listed in this publication were provided from the Woods Hole Oceanographic Institute.
- Method of cultivation: axenic culture

Test type:

static

Water media type:

saltwater

Total exposure duration:

240 h

Test temperature:

20 °C

Salinity:

30 ppt

Nominal and measured concentrations:

not reported

Details on test conditions:

TEST SYSTEM
- Test vessel: optically matched test tubes
- Material, size, headspace, fill volume: fill volume 2
- Initial cells density: "1 mL cell culture in logarithmic phase was added to 24 mL medium"
- Control end cells density: not reported
- No. of vessels per concentration (replicates): not provided
- No. of vessels per control (replicates): not provided
- The test solutions were not shaken.

GROWTH MEDIUM
- Standard medium used: yes; from Rila Products Teaneck New Jersey; artificial seawater supplemented with trace elements and vitamins

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: 12 h light / 12 h darkness
- Light intensity and quality: 6000 lux provided by fluorescence tubes
- Salinity (for marine algae): 30 ppt

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer at 525 nm, day 0 and day 10

Reference substance (positive control):

not required

Key result

Duration:

240 h

Dose descriptor:

EC50

Effect conc.:

0.75 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Based on optical density at 525 nm.

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: no

Conclusions:

240h-EC50 on Isochrysis galbana: 0.75 mg/L biomass increase (OD525 nm)

Executive summary:

In the publication from Walsh (1972) the 240 h toxicity of fenuron (technical) to the marine algae Isochrysis galbana in sea water was investigated in a 12 h light/12 h darkness cycle. The test was in general performed according to ASTM 1980. The EC50 was determined to be 0.75 mg fenuron technical/L based on biomass growth (optical density at 525 nm).

The US-EPA reviewed the data. The US-EPA document EPA/600/8-87/017 (Mayer, 1987) listed the data from Walsh (1972) and stated that all data listed are judged acceptable. Therefore the result of this study is considered to be reliable with restrictions even if only limited experimental details were provided.

Description of key information

EC50: 0.934 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

0.934 mg/L

Additional information

Several literature data are available for freshwater and marine algae. The Klimisch scores were within 2 and 3. The exposure duration of the Klimisch 2 studies was within 2 hours (oxygen production) and 240 h (biomass). The results are similar. Hence the results are considered reliable with restrictions. Studies from episammon (Arrehnius et al. 2004) were not considered since the test design deviated significantly from laboratory studies.

The EC50 was calculated as geometric mean from 5 WoE studies (freshwater and marine) since there was no significant difference in quality, impact on the test design on the results and the relevance of the data within the WoE studies. The calculation is attached to this endpoint summary.