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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000-03-14 till 2000-05-31
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Batch 29090020

OTHER SPECIFICS: Name of the test substance: Menthol rac.
Analytical monitoring:
yes
Details on test solutions:
The test substance was weighed into water and treated for 1 h with an ultrasonic batch to produce the stock stock solution (50 mg/L)
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Origin: Institute of Plant Physiology, University of Goettingen
- Cultivation: light chamber at 23 +- 2 °C and 120 µE/m2s
- Algal inoculum 10000 cells/ml initial cell density
- Illumination: 120 µE/m2s
- Cell density measured with a microcellcounter after 24, 48 and 72 hours
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23 +- 2 °C
pH:
7.5 - 10.3
Nominal and measured concentrations:
Nominal concentration: 1.25, 2.5, 5, 10, 20 and 40 mg/L (Test concentrations 1.25 and 2.5 mg/L were not analytically determined as the expected concentrations were below the detection limit of the TOC determination method (2 mg/L).
Not measured: 1.25 and 2.5 mg/L
Measured (0 h): 4, 8, 15, 29 mg/L
Measured (72 h) 3, 7, 13, 26 mg/L
Details on test conditions:
- Erlenmeyer flasks (300 mL) with stoppers
- 100 mL of test medium
- Light chamber with shaker
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
16.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 15.504 - 16.537 mg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
4.6 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
Since the original study on short-term toxicity to algae from 2000 only gives a range (> 9.8 < 18.2 mg/L) but not a distinct value for the ErC50 this value was determined by Probit analysis as ErC50 = 16.2 mg/L and quoted in the OECD SIDS report, 2003 (agreed by the ICCA initiative). The calculated ErC50 value is used as result of the underlying study on short-term toxicity to algae.
The NOEC results from the Dunnett test.

Results analysis by start of test and after 72 hours

 Nominal concentration [mg/L]  0 hours [mg/L]  72 hours [mg/L]
 control  < 2  3
 5 *w.algae  5  3
 5  4
 10  8
 20  15 13 
 40  29  26
 40 *w.algae  27  27

 *w.algae = without algal inoculum

All values refer to TOC determinations. According to the relevant product infomations 1 mg/L TOC equals to 1.3 mg/L of the test substance (empirical formula: C10H20O; molecular weight: 156.3 g/mol).

Analysis of the test concentrations 5 mg/L, 10 mg/L, 20 mg/L, 40 mg/L plus a control; additional analysis of the highest and the lowest analytically determined test concentration without algal inoculum, at test start and after 72 hours of exposure.

The test concentrations 1.25 mg/L and 2.5 mg/L were not analytically determined as the measured concentrations to be expected were below the detection limit of the TOC determination method (2 mg/L).

Before measuring TOC, the samples after 72 hours of exposure were filtered.

Validity criteria fulfilled:
yes
Remarks:
The mean of the replicate coefficients of variation in the section-by-section growth rate was 20 %; - The coefficient of variation of the mean specific rate replicates in the control not exceed 7 %
Conclusions:
During 72 hours exposure an ErC50 of 16.2 mg/L and a NOEC of 4.6 mg/L was determined.
Executive summary:

A growth inhibition study according to EU Method C.3 on algae which is equivalent to OECD Guideline for Testing of Chemicals No. 201 was performed on Desmodesmus subspicatus (former name: Scenedesmus subspicatus). Algae were exposed to 6 concentration levels (1.25, 2.5, 5, 10, 20 and 40 mg/L) of DL-Menthol for 72 h and one control without substance was performed. Cell density and pH were determined every 24 h. A 72-hour EC50 of 16.2 mg/L based on nominal concentrations was determined and NOEC resulting from Dunnett was 4.6 mg/L.

Description of key information

A growth inhibition study according to EU Method C.3 on algae which is equivalent to OECD Guideline for Testing of Chemicals No. 201 was performed on Desmodesmus subspicatus (former name: Scenedesmus subspicatus). Algae were exposed to 6 concentration levels (1.25, 2.5, 5, 10, 20 and 40 mg/L) of DL-Menthol for 72 h and one control without substance was performed. Cell density and pH were determined every 24 h. A 72-hour EC50 of 16.2 mg/L based on nominal concentrations was determined and NOEC resulting from Dunnett was 4.6 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
16.2 mg/L
EC10 or NOEC for freshwater algae:
4.6 mg/L

Additional information