Toxicity to aquatic algae and cyanobacteria.008
Administrative data
- Purpose flag:
- supporting study
- Study result type:
- experimental result
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- Study generated according to generally valid and
internationally accepted testing guideline and performed
under GLP, but the results obtained were not consistent at the highest concentration tested and Fe2O3 had an influence
on the spectroscopic measurements.
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 2004
- Report Date:
- 2004
Materials and methods
Test guideline
- Qualifier:
- according to
- Guideline:
- OECD Guideline 201 (Alga, Growth Inhibition Test)
- Deviations:
- yes
- Remarks:
- The NaHCO3 concentration of the test medium was 150 mg/L instead of 50 mg/L, as recommended by the OECD/EEC guidelines, in order to maintain a more constant pH during the test. The pH should not deviate more than 1.5 units during the test (EEC). The growt
- GLP compliance:
- yes
Test materials
- Identity of test material same as for substance defined in section 1 (if not read-across):
- no
Test material identityopen allclose all
- Identifier:
- CAS number
- Identity:
- 7775-09-9
- Identifier:
- EC number
- Identity:
- 231-887-4
- Identifier:
- EC name
- Identity:
- sodium chlorate
- Details on test material:
- Purity: 99.66%
- Analytical monitoring:
- yes
- Vehicle:
- no
Test organisms
- Test organisms (species):
- Scenedesmus subspicatus (new name: Desmodesmus subspicatus)
- Details on test organisms:
- - source: Culture Collection of Algae and Protozoa, Institute of Freshwater Ecology, Ambleside, United Kingdom.
Study design
- Test type:
- static
- Water media type:
- freshwater
- Limit test:
- no
- Total exposure duration:
- 72 h
Test conditions
- Test temperature:
- 23.0-23.7°C
- pH:
- 8.0-8.4
- Nominal and measured concentrations:
- Test concentrations: 0, 97.4, 202.2, 396.9, 793.8 and 1592.3 mg a.i./L (nominal).
Measured concentrations were higher than 80% of the nominals, therefore nominal concentrations were used for the effect calculations. - Details on test conditions:
- - Replicates: 5 test concentrations with 3 replicates, plus a control with 6 replicates
- Glassware: 100 mL glass Erlenmeyer flasks, continuous shaking
- initial cell densities of 10.000 cells/mL
- continuous light at about 91-93 µmol.s-1m-2.
- Cell concentrations were determined photometrically with a UV/VIS spectrophotometer.
Results and discussion
Effect concentrations
- Duration:
- 72 h
- Endpoint:
- NOEC
- Effect conc.:
- 1 592.3 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- test mat.
- Basis for effect:
- growth rate
- Details on results:
- - The cell density of the controls increased at least a factor 16 within 72 hours, the quality criteria have been met.
- The measured concentrations are higher than 80% of the nominal. The results are based on the nominal concentrations.
- The extinction at the beginning of the test is higher in the test solutions than in the control. The Fe2O3 present in the test substance is most likely the cause of this increase. At the highest test concentration a small decrease of the extinction was observed after 24 h. This is probably caused by the precipitation of Fe2O3. This phenomenon is considered to have a negligible impact on the final result. However the growth rate at this concentration was calculated using only the extinctions at the beginning and at the end of the test.
There is no significant effect on the growth rate of Scenedesmus subspicatus.
For the biomass a 9% response was found at a test concentration of 794 mg/L and a 22% response was found at the highest test concentration of 1592.3 mg/L. An EbC50 of 3665 mg/L is calculated after extrapolation. NOEC (biomass) = 396.9 mg/l - Reported statistics and error estimates:
- Results of the toxicity test were interpreted by probit analysis. All computations were performed using the TOXCALCTM 5.0 program.
- Any other information on results incl. tables:
Remark => The reviewer finds it more accurate to say that the EbC50 is higher than 1592.3 mg/l, the highest concentration tested. An ErC50 is not given in the report, but it can also be stated that this is higher than 1592.3 mg/l. The NOEC (growth rate) = 1592.3 mg/l The increase in extinction most likely caused by Fe2O3, is not considered to have a significant impact on the results of this test. In the calculation of the biomass a correction is made for the higher extinctions measured at t=0. The higher values at t=0 do not have an influence on the slope of the growth curve, which is used for the calculation of the growth rate. Therefore these results are considered to be accurate.
Applicant's summary and conclusion
- Conclusions:
- Sodium chlorate is not very toxic to Scenedesmus subspicatus. The highest test concentration of 1595 mg/l gave only a 22% biomass inhibition response.
It was therefore not possible to calculate reliable EC50 values for both the inhibition based on biomass and growth rate.
The NOEC determined from the results is 396.9 mg/l, the LOEC is 793.8 mg/l. - Executive summary:
- In order to predict effects of Sodium chlorate in an aquatic environment, the toxicity of this chemical to freshwater algae was assessed. The algal toxicity was determined in the Algal Growth Inhibition test in accordance with OECD, EEC and IS0 test guidelines and with the OECD Principles of Good Laboratory Practice. The guidelines were slightly modified to ensure good growth and pH control of the cultures.The green algae Scenedesmus subspicatus was exposed to the following final nominal test concentrations: 97.4 - 202.2 - 396.9 - 793.8 and 1592.3 mg/l of sodium chlorate.The toxicity of sodium chlorate to an exponentially growing culture of Scenedesmus subspicatus was determined over an exposure period of 72 hours. Sodium chlorate is not very toxic to Scenedesmus subspicatus. The highest test concentration of 1595 mg/l gave only a 22% biomass inhibition response.It was therefore not possible to calculate reliable EC50 values for both the inhibition based on biomass and growth rate.The NOEC determined from the results is 396.9 mg/l, the LOEC is 793.8 mg/l. The test was conducted in a mineral salts medium in a climatized illuminated orbital incubator. The maximum variation in pH in the test media was 0.4 pH unit.The definitive test is valid as shown by the increase of the extinction of the control over 72 h by a factor of 26.The chemical analyses carried out showed that the concentration of the test compound during the test remained within 80% of the concentration at the beginning of the test. The results are based on nominal concentrations.
- Validity criteria fulfilled:
- yes
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