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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, near guideline, experimental study, published in peer reviewed literature; minor restrictions in design and/or reporting but otherwise adequate for assessment.
Qualifier:
according to
Guideline:
other: DIN 38 412, Part 9 (draft standard) 1988
Deviations:
yes
Remarks:
Modified procedure for volatile substances. 250 mL bottles used with ground-glass stoppers and with an overall test time of 48 hours.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
no
Details on sampling:
No data reported
Vehicle:
not specified
Details on test solutions:
In order to produce the test solutions, water-soluble substances were quantitatively dissolved to produce an optically clear stock solution in 800 mL double-distilled water using magnetic stirrers (max 24 hours). Before beginning the test, the stock solutions of the substances to be tested were adjusted to pH 8.0±0.3 whereby the concentration of the acid or base was selected so as to ensure that the volume added remained small. When testing volatile substances (e.g. 1,3,5-trimethylbenzene) the procedure was modified and 250 mL wide-neck bottles with ground-glass stoppers were used. The parallel dilution series (f=2) was set up in the following way: the volume of dilution water (e.g. 27.5 mL) corresponding to the dilution level (e.g. 1:4 of the test medium) was pre-filled into each of the six bottles for the conentration level. Then, 5 mL of the 10-fold concentration of the nutrient solution and the corresponding volume of the test preparation (stock solution) (e.g. 12.5 mL) for the desired concentration was added to each test vessel. The bottles were closed immediately. Finally, the stopper was lifted briefly to add 5 mL of the algae suspension of the preliminary culture.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Strain number 8681 SAG. A strain that has been maintained over a number of decades in submerged culture. For this purpose, the required number of 100 mL Erlenmeyer flasks with metal caps containing 20 mL nutrient solution were sterilised in a steam steriliser for 30 minutes on 2 consecutive days. After cooling, the contents of each flask were inoculated with 2 mL cell suspension taken from a 10 day old stock culture. The inoculated flasks were placed on a white surface, protected from daylight and exposed to constant light from two parallel fluorescent Osram 40W/30 tubes, at 24 ± 1°C and relative humidity of 50%. To maintain the test strain, fresh stock cultures were prepared at 10 day intervals.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
No data reported
Hardness:
No data reported
Test temperature:
24 ± 1°C
pH:
8.0± 0.3
Dissolved oxygen:
No data reported
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal tested concentration range 0.40 - 50 mg/L
Details on test conditions:
Constant lighting provided by OSRAM l 25/40 fluorescent tubes; each of the positions for the test preparation had an irradiance E = 17.0 W/m2. Temperature and arradiance are given as manipulated variables.
Reference substance (positive control):
not specified
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
8.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
16 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
53 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Assumed to be extrapolated
Details on results:
No data reported
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
The area under the growth curve (integral of biomass with time) was calculated according to the given equation and from this was calculated the percentage inhibition of cell multiplication during the test for each concentration level on the basis of a comparison of the biomass formed under the influence of the substance with the biomass in the control population.
The average growth rate for cultures showing exponential growth was calculated and on this basis, the growth related inhibition was calcualted from the difference between the growth rates under the influence of the substance and the growth rate in the control. The growth rate, as stipulated by DIN 38 312 Part 9 in the test procedure, was expressed by means of the logarithm of the change in the cell count.
The tested concentration was assigned to the respective inhibition values in the probability paper. The regression line was determined and from this could be read the desired EC10 and EC50 values.
Validity criteria fulfilled:
yes
Remarks:
16 fold increase in cell growth confirmed for control in 48 hours, meets DIN 38 412 part 9 criteria.
Conclusions:
The reported experimental 48 hour EC50 for Scenedesmus subspicatus was determined to be 25 mg/L based on biomass and 53 mg/L based on growth rate. The 48 hour EC10 was determined to be 8.1 mg/L based on biomass and 16 mg/L based on growth rate.
Executive summary:

This robust summary has a reliability rating of 2 because it is a non-GLP, near guideline, experimental study, published in peer reviewed literature; minor restrictions in design and/or reporting but otherwise adequate for assessment. Since there is no information in the article to suggest that the data are invalid it can be considered suitable as the key study for this endpoint. The reported experimental 48 hour EC50 for Scenedesmus subspicatus was determined to be 25 mg/L based on biomass ad 53 mg/L based on growth rate. The 48 hour EC10 was determined to be 81 mg/L based on biomass and 16 mg/L based on growth rate. The result does not indicate that 1,3,5-trimethylbenzene (mesitylene) would meet the criteria for toxic in the PBT assessment. This endpoint will not affect the classification of the substance since a lower LC50 is found for Daphnia magna which will determine the classification.

Description of key information

The reported experimental 48 hour EC50 for Scenedesmus subspicatus was determined to be 25 mg/L based on biomass and 53 mg/L based on growth rate. The 48 hour EC10 was determined to be 8.1 mg/L based on biomass and 16 mg/L based on growth rate.

Key value for chemical safety assessment

EC50 for freshwater algae:
53 mg/L

Additional information

The Kuhn and Pattard (1990) study is a non-GLP, near guideline, experimental study, published in peer reviewed literature with minor restrictions in design and/or reporting but otherwise adequate for assessment. Since there is no information in the article to suggest that the data are invalid, it can be considered suitable as the key study for this endpoint. The 48 hour EC50 value for green algae (Scendesmus subspicatus) was 25 mg/L based on biomass and 53 mg/L based on growth rate. The 48 hour EC10 value was 8.1 mg/L based on biomass and 16 mg/L based on growth rate.

A QSAR calculation using the ECOSAR model gives an estimated 96 hour EC50 for green algae of 3.19 mg/L.