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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
Study period:
2002
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
After 24, 48, and 72 hours, the cell growth was determined by counting.
Vehicle:
yes
Details on test solutions:
Vehicle acetone 0.01 % (v/v)

Preparation of test solution (TS):
A 143 mg/mL stock solution was prepared by the direct addition of piperonyl butoxide to acetone. The stock solution was diluted with acetone to nominal concentrations of 70, 35, 18, 9 and 4.5 mg/mL.
Two control treatments were prepared, one containing algal nutrient medium only and the other was prepared by the addition of acetone (0.1 mL/L) to algal nutrient medium.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
Species: Selenastrum capricornutum
Strain: CCAP 278/4
Source: Culture Collection of Algae and Protozoa, Institut of freshwater Ecology, Ambleside, Cumbria, UK
Laboratory culture: Yes, semi-axenic
Method of cultivation: not stated
Pretreatment: not stated
Initial cell concentration: Nominally 10000 cells/mL
Limit test:
no
Total exposure duration:
72 h
Test temperature:
See the table "Cell concentration data" attached in background material
pH:
See the table "Cell concentration data" attached in background material
Dissolved oxygen:
Aeration of dilution water: not stated
Details on test conditions:
TEST SYSTEM
Volume of culture flasks: 250 mL Erlenmeyer glass flasks. The final volume in each test vessel was 100 mL.
Culturing apparatus: 100 mL quantities of test medium were added to five flasks for each of the control, 0.45, 0.90, 1.8, 3.5, 7.0 and 14.3 mg/L treatments. Eight flasks were prepared with the solvent control medium. One of each flask per treatment was used to determine a background electronic count and one for determining water quality. Further equipment: HPLC-UV apparatus
Procedure for suspending algae: not stated
Number of vessels/ concentration: 3. The control was tested in 6 parallel cultures
Test performed in closed vessels due to significant volatility of TS: No

CULTURE MEDIUM
Culture medium: the cell density was adjusted to an initial concentration of 104 cells/mL in each test vessel. Composition (minerals, hardness) of algal growth medium according to OECD guideline #201.
The algal culture medium was autoclaved before the addition of NaHCO3. The NaHCO3 was added to the algal culture medium after filter sterilisation (0.2 µm filter)

OTHER TEST CONDITIONS
Light intensity: 6760-7940 lux
Light quality: Constant illumination from the top by a cooled orbital incubator (100 cycles/min)
Photoperiod: Continuous illumination

TEST PARAMETER
Inhibition of (i) area under the growth curve (AUC) and (ii) specific growth rate (μ)

MONITORING OF TS CONCENTRATION
The determination of active ingredients from water samples was performed by HPLC-UV analysis at point zero and after 72 h.
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.824 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
3.89 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.09 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
biomass
Details on results:
RESULTS TEST SUBSTANCE
- Initial concentrations of test substance:
Nominal concentrations were 0.45, 0.90, 1.8, 3.5, 7.0 and 14.3 mg/L Piperonyl Butoxide, based on the results of a range finding test.
- Actual concentrations of test substance:
See the graphic "ACTUAL CONCENTRATIONS" attached in backdground material.
- Growth curves:
See the graphic "GROWTH CURVES" attached in backdground material.
- Concentration/response curve:
See the graphic "CONCENTRATION-RESPONSE CURVE" attached in backdground material.
- Cell concentration data:
See the table "Cell concentration data" attached in background material.
- Effect data (cell multiplication inhibition):
EbC50: 2.09 mg mg Piperonyl Butoxide/L (with 95% confidence limits of 1.90 to 2.3 mg/L)
ErC50: 3.89 mg Piperonyl Butoxide/L
NOErC: 0.824 mg Piperonyl Butoxide/L
- Other observed effects:
Piperonyl Butoxide showed significant inhibitory effects on algal growth at concentrations above or equal to 1.78 mg/L.

RESULTS OF CONTROLS
No inhibitory effects were observed

TEST WITH REFERENCE SUBSTANCE
Not performed
Reported statistics and error estimates:
The EC values (EbC, ErC, LOEC, and NOEC) were calculated using probit analysis after log10 transformation of the mean measured exposure concentrations. The highest no observed effect concentrations (NOEC) were determined from the results of an analysis of variance at p=0.05. The significance of differences in the mean A and µ values between the solvent control and all remaining treatments were calculated using Dunnett’s test.

RESULTS AND DISCUSSION

Based on the results of this study the highest no observed effect level (NOEC) of Piperonyl Butoxide to S. capricornutum was calculated to be 0.824 mg/L.

NOErC = 0.824 mg Piperonyl Butoxide/L (based on measured concentration)

ErC50 = 3.89 mg Piperonyl Butoxide/L (based on measured concentration)

EbC50 = 2.09 mg mg Piperonyl Butoxide/L (based on measured concentration)

Validity criteria fulfilled:
yes
Remarks:
according to OECD Guideline 201
Conclusions:
Validity criteria can be considered as fulfilled (see validity criteria summarized in the table "VALIDITY CRITERIA" attached in background material.)
Based on the results of this study the highest no observed effect level (NOEC) of Piperonyl Butoxide to S. capricornutum was calculated to be 0.824 mg/L.
Reliability: 1
Deficiencies: No
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1990
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
not specified
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Limit test:
no
Duration:
72 h
Dose descriptor:
other: ErC50
Effect conc.:
0.5 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
other: EbC50
Effect conc.:
0.17 mg/L
Nominal / measured:
not specified
Conc. based on:
not specified
Basis for effect:
growth rate

Description of key information

ErC50 0.5 mg/l

EbC50 0.17 mg/l

NOEC 0.824 mg/l

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
0.824 mg/L

Additional information

Test organism: Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)