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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Documentation inssufficient for assessment: data is lacking on many parameters like the test substance, test organisms, test concentration
Principles of method if other than guideline:
The concentration of the algal suspension was determined by measuring turbidity at 578 nm in a layer of 10 mm thickness. The threshold concentration for growth inhibition was set at a mean extinction value of 3% below the mean value of the extinction value for non-toxic dilutions of the test cultures.
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
not specified
Details on test solutions:
Stock solutions of the substance were prepared in sterile double-distilled water. The pH was not adjusted. Dilutions were prepared using sterile double-distilled water containing 1 part v/v of pollutant solution in 2 to 214 parts v/v mixture. Two parallel dilution series were prepared in 300-ml Erlenmeyer flasks each containing 40 ml of growth medium. Each flask from the dilution series was inoculated to 50 ml by adding 5 ml each of the stock solution and 5 ml each of the algal suspension of the preliminary culture having a known adjusted extinction value.
Test organisms (species):
Scenedesmus quadricauda
Details on test organisms:
TEST ORGANISM
- Common name: fresh water algae
- Strain: Scenedesmus quadricauda
- Age of inoculum (at test initiation): 10 days
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Remarks on exposure duration:
Extinction was only measured at the start and after 7 d of exposure.
Post exposure observation period:
Not performed.
Test temperature:
27°C
pH:
pH not adjusted to take into account the pH of the pollutant solution
Nominal and measured concentrations:
No data
Details on test conditions:
The Erlenmeyer flasks with algal suspensions were incubated on a white surface protected against daylight and exposed to constant lighting by luminescent worm white tubes at 60cm distance from each other, at 27°C and a relative humidity of 50%. Determination of cell concentrations: spectrophotometer (measurement of the extinction of the monochromatic radiation at 578 nm in a 10-mm layer of cell suspension). The flasks were shaken once a day. Exposure period was 7 days.
Duration:
7 d
Dose descriptor:
other: TGK
Effect conc.:
2.9 mg/L
Basis for effect:
other: 3% reproductive inhibition
Reported statistics and error estimates:
For evaluation of the toxicological findings at the end of the test period, the mean value (A) of the extinction is calculated for all test cultures that are free from both toxic influence and stimulation of growth except for those having extinction values outside a standard deviation of < 3% and also, the mean value (B) of the extinction for those test cultures having the lowest toxic pollutant concentration within the dilution series.
For mathematical evaluation by means of a suitable electronic calculator (a) (highest non-toxic pollutant concentration) is plotted against (A) and (b) (lowest toxic pollutant concentration) against (B) as coordinates. After entering (A - 3%), the pollutant concentration at which the inhibitory action (c) begins may be obtained from the regression line between (a;A) and (b;B) if a negative deviation of the mean extinction by a 3% difference against the mean extinction value for all test cultures having a non-toxic and non-stimulating pollutant concentration is used as an indicator of the beginning of inhibitory action.
Conclusions:
Diallyl phthalate was found toxic for Scenedesmus quadricauda at the threshold concentration of 2.9 mg/l
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
other: DIN 38412, Part 9
Deviations:
not specified
GLP compliance:
not specified
Analytical monitoring:
not specified
Vehicle:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Green algae
- Strain: Scenedesmus subspicatus N° 8681 SAG
- Age of inoculum (at test initiation): 10 day old
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Post exposure observation period:
Measurements at the beginning of the test and after 24, 48, 72 & 96 hr
Nominal and measured concentrations:
Nominal: concentration range 0.63 - 80 mg/l
Details on test conditions:
TEST SYSTEM
- Test vessel: 300 ml erlenmeyers flasks
- Type (delete if not applicable): covered with metal caps
- Initial cells density: 10000 cells/ml

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Light intensity and quality: E = 17.0 W/m2

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: measurement of optical density (turbidity) using the Eppendorf digital photometer
Reference substance (positive control):
yes
Remarks:
Potassium dichromate, cadmium chloride
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
5.5 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
growth rate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
11 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
3 mg/L
Basis for effect:
growth rate
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
1.9 mg/L
Basis for effect:
growth rate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
5.3 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
3.8 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
4.5 mg/L
Nominal / measured:
nominal
Conc. based on:
dissolved
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
1.9 mg/L
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
1.6 mg/L
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Duration:
96 h
Dose descriptor:
EC10
Effect conc.:
2.6 mg/L
Basis for effect:
biomass
Remarks:
based on measurement of turbidity
Details on results:
EC10 values indicate recovery of algal growth during the exposure period probably due to degradation of the test substance.
Results with reference substance (positive control):
Potassium dichromate: 96h-EbC50=0.35 mg/l
Cadmium chloride: 96h-EbC50=0.15 mg/l
Reported statistics and error estimates:
Reference to control growth was based on the average values of different control preparations. Assessment of effects on growth was performed on the basis of logarithmic groth versus time. Algal growth in the controls showed a shift from exponential to stationary phase after 48h. Hence, no values for growth rate could be given after 72h when the stationary phase was already reached. Data were evaluated by establishing the growth curves, calculating the area under the growth curve and calculating the differentiates of the exponential phase to assess growth rates. EC-values were determined by assigning the tested concentrations to the respective inhibition values on probability paper.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the study, diallyl phthalate was found to affect algal growth at concentrations above 1.6 mg/l (EC10 for biomass) with an EC50 for biomass corresponding with 3.8 mg/l (72h).

Description of key information

The key information is based on a peer reviewed and published study. The key values are based on the EC10 and EC50 values for the 72h period as these were lower than those for the 48h period, although exponential growth decreased after 48h in the controls. Results of an additional publication support the key values chosen.
Acute toxicity was in agreement with data from a GLP study reported elsewhere in this file.

Key value for chemical safety assessment

EC50 for freshwater algae:
3.8 mg/L
EC10 or NOEC for freshwater algae:
1.6 mg/L

Additional information

Reference to control growth was based on the average values of different control preparations. Algal growth in the controls showed a shift from exponential to stationary phase after 48h. Hence, no values for growth rate could be given after 72h when the stationary phase was already reached. In the case of diallyl phthalate, the EC10 and EC50 values correspond with the 72h period as these were lower than those determined for the 48h period. (Bringmann & Kühn, 1980)