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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:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Some details are missing on validation criteria. unsure whether the endpoint is growth rate
Qualifier:
according to guideline
Guideline:
other: US EPA Algal, Selenastrum capricornutum, growth test Method 1003.0. In: Short-term methods for estimating the chronic toxicity of effluent and receiving waters to freshwater organisms. EPA 600/4-89/001, Cincinnati OH
GLP compliance:
no
Analytical monitoring:
no
Remarks:
results based on nominal concentrations
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 ± 1°C
pH:
7.45
Nominal and measured concentrations:
full range starting around 0.35 and ending around 14 mg/L
Details on test conditions:
6 concentrations in triplicate
the test also investigated the effect of the level of P (phosphorus) levels, here only the results at 6 µM of P are provided since this is the recommended value in test media
Reference substance (positive control):
not required
Key result
Duration:
72 h
Dose descriptor:
IC50
Effect conc.:
2.19 mg/L
Basis for effect:
growth rate
Remarks on result:
other: result at 6 µM of P, the recommended value. unsure whether the endpoint is growth rate
Key result
Duration:
72 h
Dose descriptor:
IC10
Effect conc.:
> 1 - <= 1.5 mg/L
Basis for effect:
growth rate
Remarks on result:
other: result at 6 µM of P, the recommended value. unsure whether the endpoint is growth rate
Details on results:
72h inhibition (unsure whether the endpoint is growth rate) at pH 7.45 and 1 mg/L of test item in medium:
- IC50: 2,19 mg/L
- IC10 graphically determined as ranging > 1-1,5 mg/L
Validity criteria fulfilled:
not specified
Conclusions:
Algae IC50-(72h) of the test item is 2,19 mg/L, and the IC10 ranges > 1-1.5 mg/L. It is unsure whether the endpoint is growth rate.
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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Some details are missing on test medium and validation criteria. Moreover the exposure duration is 48h instead of 72h recommended. The initial pH is too low (6.5) compared to 7.5-8.1 recommended.
Qualifier:
no guideline followed
Principles of method if other than guideline:
The test technique used is a closed-system algal toxicity test.
Algal inoculum under a steady state was transferred into 300mL BOD bottles containing dilution water (with growth medium) and toxicants. The bottles were then placed on an orbital shaker operated at 100 rpm.
The algal growth rate based on cell density counts was then evaluated.
The population density of the algae was determined using an electronic particle counter (Culter Electronics, Luton, UK).
All chemicals used were of reagent grade and were tested at least twice, i.e., range finding test and definitive test. For the definitive test, one control and 6 (or 7) different treatments were performed in triplicate.
Probit analysis was applied to determine the concentration–response relationship and the median effective concentration (EC50). One-tail Dunnett’s procedure was applied for the estimation of NOEC and LOEC values at 5% level of significance.
GLP compliance:
no
Analytical monitoring:
no
Remarks:
initial concentrations only
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
other: Dilution water
Limit test:
no
Total exposure duration:
48 h
Test temperature:
24 ± 1 °C
pH:
6.5
Nominal and measured concentrations:
Concentration range: 0.40 to 38.4 mg/L
Reference substance (positive control):
not required
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
15.9 mg/L
Basis for effect:
growth rate
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
3.2 mg/L
Basis for effect:
growth rate
Validity criteria fulfilled:
not specified
Conclusions:
Algae growth rate EC50-(48h) and NOEC of the test item are respectively 15.90 mg/L and 3.20 mg/L.

Description of key information

Two study reports in which representative guideline test organism (Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum) are available with the following endpoints:

  • Algae IC50-(72h) of the test item is 2,19 mg/L, and the IC10 ranges from > 1 to < 1.5 mg/L. It is unsure whether the endpoint is growth rate
  • Algae growth rate EC50-(48h) and NOEC of the test item are respectively 15.90 mg/L and 3.20 mg/L

Based on these endpoints, gallic acid is not classified for aquatic hazards.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.19 mg/L
EC10 or NOEC for freshwater algae:
1 mg/L

Additional information