4-Hydroxy-3,5-dimethylbenzonitrile

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:

2003-11-14 to 2004-02-26

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:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method: duplicate samples were taken before the start of the test and after 72 hours from each test medium and from the control (all without algae).
- Sample storage conditions before analysis: the samples were deep-frozen (~-20°C) immediately after sampling.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test medium of the highest test nominal concentration of 100 mg/L was prepared by dissolving 50.1 mg T002251 in 500 mL of test water by ultrasonic treatment (15 minutes) and intense stirring for 1 hour at room temperature in the dark. The lower test item concentrations were prepared by dilution.
- Controls: yes

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain:n° 86.81 SAG
- Source (laboratory, culture collection): Collection of Algal Cultures (SAG, Institute for Plant Physiology, University of Göttingen, D-37073 Göttingen, Germany)
- Method of cultivation: in the RCC laboratories under standardized conditions according to the test guideline (OECD 201)

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions (same as test or not): same as the test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

24 mg CaCO3/L

Test temperature:

22-23°C

pH:

At the start of the test: 7.6 - 8.0
At the end of the test: 7.9 - 8.2

Dissolved oxygen:

not reported

Salinity:

not applicable

Nominal and measured concentrations:

nominal test concentrations (mg/L) : 1.0, 3.2, 10, 32, 100
mean measured concentrations (mg/L) : -, 3.08, 10.1, 31.6, 103

The mean measured concentrations (calculated as the average over all measurements per test concentration) ranged from 96% to 104% of nominal.

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type (delete if not applicable): covered with glass dishes
- Material, size, headspace, fill volume: 50 mL Erlenmeyer flasks filled with 15 mL algal suspension
- Initial cells density: 10,000 cells/mL
- Control end cells density: 32 x 10,000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (OECD 201)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic test water
- Culture medium different from test medium: no
- Intervals of water quality measurement:
* temperature: daily
* pH: at the begin and the end of the test

OTHER TEST CONDITIONS
- Sterile test conditions: no information
- Adjustment of pH: no
- Photoperiod: continuous illumination
- Light intensity and quality: mean of 8500 lux (range: 7670-9160 lux) by fluorescent tubes (Philips TLD 36W-1/840)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter
- effect calculated parameters: specific growth rate and biomass (area under the growth curve)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: x3.2
- Range finding study
- Test concentrations:data not shown
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (tested at least once a year)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

27.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 16.6-46.6

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: clear test medium except in the highest test concentration where noticeable coloration (slightly yellowish-brown) was caused by the test item.
- EC50 (biomass) = 21.1mg T002251 /L.
- EC10 (growth rate) = 10.2 mg T002251 /L.
- EC10 (biomass) = 8.6 mg T002251 / L.
- EC90 (growth rate) = 75.0 mg T002251 / L.
- EC90 (biomass) = 51.8 mg T002251 / L.
- LOEC (growth rate and biomass) = 32 mg T002251 / L.
- NOEC (biomass) = 10 mg T002251 / L.

Results with reference substance (positive control):

not data reported except that the latest result of the positive control test showed that the toxic performance was valid and within the historical range in the RCC laboratory.

Reported statistics and error estimates:

EC50 (biomass and growth rate) and corresponding EC10, EC90 values and their 95% confidence intervals were calculated by Probit analysis.
NOEC and LOEC values were determined using a Dunnett-test

Validity criteria fulfilled:

yes

Conclusions:

A 72-h growth inhibition test with the unicellular green alga Scenedesmus subspicatus was performed according to the OECD 201 guideline. The results were based on nominal concentrations. The 72-h EC50 (growth rate) was determined to be 27.6 mg T002251/L and the 72-h NOEC was determined to be 10 mg T002251/L. The results of the test can be considered reliable without restrictions.

Description of key information

The study of Seyfried (2004), investigating the acute toxicity of T002251 to algae according to OECD guideline 201, was considered as the key study for endpoint coverage. The 72-h NOEC and 72-h EC50 for growth rate (based on nominal concentrations) were determined to be 10 mg/L and 27.6 mg/L respectively. The substance can be considered as harmful to algae.

Key value for chemical safety assessment

EC50 for freshwater algae:

27.6 mg/L