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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Justification for type of information:
Read-across toxicity studies in algae on one closely structural and physicochemical related substance: Benzoic acid.
For further read-across justification se document attached in section 13
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across: supporting information
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
101.1 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
11.7 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Validity criteria fulfilled:
not specified
Conclusions:
Based on read-across to benzoic acid, the following effect concentrations were identified:
EC50 (Pseudokirchneriella subcapitata) = 101.1 mg/L (growth rate)
NOEC ( Pseudokirchneriella subcapitata) = 11.7 mg/L
Executive summary:

Based on read-across to benzoic acid, the following effect concentrations were identified:

EC50 (Pseudokirchneriella subcapitata) = 101.1 mg/L (growth rate)

NOEC ( Pseudokirchneriella subcapitata) = 11.7 mg/L

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2003
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Version / remarks:
ISO 8692-1989-11-15, 1989. Water quality––Fresh water algal growth inhibition test with Scenedesmus subspicatus and Selenastrum capricornutum. First edition. ISO, Geneve,
Switzerland.
Deviations:
not specified
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information): no data
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Scenedesmus sp.
Details on test organisms:
Cultures of S. subspicatus were obtained from the National Institute of Biology (NIB, Ljubljana, Slovenia). The test design was to incubate an algal culture for several generations to obtain asynchronous exponential growth under test conditions using a geometric dilution series of 10 concentrations.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Hardness:
no data
Test temperature:
no data
pH:
8.3+/-0.2
Dissolved oxygen:
no data
Nominal and measured concentrations:
A geometric dilution series of 10 concentrations
Details on test conditions:
mineral medium, composed for the test as follows (mg/l): NH4Cl = 15; MgCl2 x 6H2O = 12; CaCl2 x 2H2O = 18; MgSO4 x 7H2O = 15; KH2PO4 = 1.6; NaHCO3 = 50
and (ug/l): FeCl3 x 6H2O ? 80; Na2EDTAx 2H2O = 100; H3BO3 = 185; MnCl2 x4H2O = 415; ZnCl2 = 3; CoCl2 x6H2O = 1.5; CuCl2 x 2H2O = 0.01 and Na2MoO4 x2H2O = 7
Reference substance (positive control):
not specified
Key result
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
333 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
no data
Validity criteria fulfilled:
not specified
Conclusions:
7 d-EC50 of benzoic acid to Scenedesmus subspicatus was 333 mg/L based on the growth rates.
Executive summary:

The toxicity of benzoic acid towards algae (Scenedesmus subspicatus) was tested applying a modified ISO 8692 Guideline. The test design was to incubate an algal culture for several generations to obtain asynchronous exponential growth under test conditions using a geometric dilution series of 10 concentrations. Based on the endpoint growth rate the 7-d-EC50 was determined to be 333 mg/L.

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
Closed system algal toxicity test. For more details see: Jui-Ho Lin, Wei-Chen Kao, Kuo-Pei Tsai, Chung-Yuan Chen (): A novel algal toxicity testing technique for assessing the toxicity of both metallic and organic toxicants. Water Research 39 (2005) 1869–1877
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The alga Raphidocelis subcapitata (formerly known as Selenastrum capricornutum, UTEX 1648) was grown in a 4-L transparent chemostat incubator. The growth medium was continuously supplied by a variable-speed pump (flow rate ¼ 1 L=day). Air agitation was used to achieve adequate mixing. The chemostat reactors were placed in a constant-temperature room at 24+/-1C. Light intensity was set at 65 uE m2 s-1.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
no data
Test temperature:
24 +/-1
pH:
8.3+/-0.2
Dissolved oxygen:
no data
Nominal and measured concentrations:
A geometric dilution series of 10 concentrations
Details on test conditions:
After the algal incubator has reached the steady state, toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with growth medium), and toxicants into 300-mL BOD bottles. The BOD bottles were completely filled up with no head space left. Water seal was provided to ensure a closed-test environment. The bottles were then placed on an orbital shaker (Ferstek, Model S103) operated at 100 rpm. Temperature and light intensity were kept the same as the algal incubator. US EPA (1996) bottle medium with no ethylenediaminetetraacetic acid (EDTA) content was used for toxicity testing. The dilution water was stripped by nitrogen gas to reduce the initial dissolved oxygen level to approximately 1–3 mg/ L. In addition, the N2 gas contained 0.5% carbon dioxide as an extra carbon source. The initial pH for the growth medium was 7.5. Three response endpoints were used to evaluate the toxicity of toxicants; dissolved oxygen production (DDO), the delta cell density, and the algal growth rate based on cell density. The median effective concentration (EC50) was defined as the toxicant concentration that resulted in 50% reduction with respect to the response endpoints (i.e., DeltaDO, Deltacell density and growth rate). In a preliminary study, test conditions (in terms of the initial cell densities and test duration) were optimized through a series of trial-anderror tests. The objective of these trials was to achieve maximum test sensitivity and, yet, maintain satisfactory reproducibility. In general, lower cell densities resulted in higher sensitivity with poorer test repeatability. Furthermore, longer exposure time may increase the test sensitivity but, in some instance, result in insufficient carbon supply due to the excessive production of algal biomass. The optimum inoculated cell density and the test duration were 15,000 cells/mL and 48 h, respectively. Toxicant concentrations presented in this work are in the form of nominal concentration. Concentration controls were periodically conducted following exactly the same procedure as described above. The only difference is that no algal inoculum was added to the concentration controls. The prepared controls were then analyzed using an atomic absorption spectrophotometer (Hitachi, Model Z-8100) or a HPLC analyzer (Waters, 2996 Photodiode Array Detector). The difference between the nominal and measured concentrations was found to be less than 6%. All chemicals used were of reagent grade. All tests were performed in triplicate.
Reference substance (positive control):
not specified
Key result
Duration:
2 d
Dose descriptor:
EC50
Effect conc.:
83.29 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
Duration:
2 d
Dose descriptor:
NOEC
Effect conc.:
9.62 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Results with reference substance (positive control):
no data
Validity criteria fulfilled:
not specified
Conclusions:
The toxicity of benzoic acid towards algae ( Pseudokirchneriella subcapitata) was tested. Based on the endpoint growth rate the 2-d-EC50 was determined to be 83.3 mg/L and the NOEC to 9.62 mg/L. .
Executive summary:

The toxicity of benzoic acid towards algae ( Pseudokirchneriella subcapitata) was tested. Based on the endpoint growth rate the 2-d-EC50 was determined to be 83.3 mg/L and the NOEC to 9.62 mg/L. .

Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
101.1 mg/L
EC10 or NOEC for freshwater algae:
11.7 mg/L

Additional information

Based on read-across to benzoic acid, the following effect concentrations were identified:

EC50 (Pseudokirchneriella subcapitata) = 101.1 mg/L (growth rate)

NOEC ( Pseudokirchneriella subcapitata) = 11.7 mg/L