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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
Study period:
28 September 2000 through 15 February 2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Nectaryl :
- Batch No. : 9000368697
- Purity : 97.1% (sum of 3 peaks)
- Expiry Date : 07 August 2002
Analytical monitoring:
yes
Remarks:
HPLC-UV/VIS
Details on sampling:
Test samples were taken for analysis at Time 0, after 24 hours exposure and at the end of the study, at 72 hours.

All samples which were not analysed on the same day as sampling were stored deep frozen. On the day of analysis, the frozen samples were defrosted at room temperature.
Vehicle:
no
Remarks:
Water saturated fractions were prepared.
Details on test solutions:
A water saturated fraction with a loading rate of 100 mg Nectaryl/L was prepared. The solution was prepared by stirring for three days. The test solution was allowed to stabilise. The water fractions were then separated from the excess of test item.

Dilutions were prepared directly from the 100 mg/L loading-rate using algal medium to obtain the following Nominal dilutions :
100% (Loading Rate 100 mg/L)
46% (Loading Rate 46 mg/L)
22% (Loading Rate 22 mg/L)
10% (Loading Rate 10 mg/L)
4.6% (Loading Rate 4.6 mg/L)
2.2% (Loading Rate 2.2 mg/L)
1.0% (Loading Rate 1 mg/L)
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
-Selenastrum capricornutum - Strain CCAP 278/4;
- Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously areated and exposed to light (4000 - 9000 Lux) in a climate room at a temperature of 23 +/- 2 °C. Three days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 20,000 cells/mL. The pre-culture was maintained under the same conditions as used in the test. The cell density was measured directly before use.
Test type:
static
Water media type:
freshwater
Remarks:
M2 medium
Limit test:
no
Total exposure duration:
72 h
Hardness:
24 mg CaCO3/L
Test temperature:
Start : 21.4 °C
During : 23.5 °C
pH:
pH range :

Concn. Level Exposure Time
(% saturation) 0 hours 72 hours

Control 8.2 8.5
1.0 8.2 8.2
2.2 8.2 8.2
4.6 8.2 7.9
10 8.0 7.9
22 7.7 7.8
46 7.4 7.7
100 7.0 7.7
Nominal and measured concentrations:
Water saturated fraction were prepared starting with a 100 mg/L laoding rate stock which underwent subsequent dilution

The geometric mean of the Time 0, 24 hours and 72 hours analyses has been calculated

Exposure Concn. (Dilution) Geometric Mean Concn. (mg/L)
100% (Loading Rate 100 mg/L) 7.0
46% (Loading Rate 46 mg/L) 3.7
22% (Loading Rate 22 mg/L) 1.9
10% (Loading Rate 10 mg/L) 0.76
4.6% (Loading Rate 4.6 mg/L) 0.34
2.2% (Loading Rate 2.2 mg/L) 0.16
1.0% (Loading Rate 1 mg/L) 0.07
Control Not Detected
Details on test conditions:
- Test Type : Static
- Test Vessels : 100 mL, glass
- Medium : M2 medium according to the ISO-Standard "Algal Growth Inhibition Test", November 1989
- Cell Density : A volume of 1 mL of the pre-culture was added to each replicate containing 50 mL of test medium providing a cell density of 10,000 cells/mL
- Test Duration : 72 hours
- Lighting/Ilumination : Continuous lighting using 30 Watt TLD lamps with a light intensity within the range 76 - 98 microEm-2s-1
- Incubation : During incubation the algal cells were kept in suspension by continuous shaking in a climatised incubator.
Reference substance (positive control):
yes
Remarks:
Potassium Dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.9 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.32 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.46 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.07 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: NOEC for both Growth Rate and Biomass
Details on results:
In the Controls, the cell density increased by a factor of > 90 within the 72 hours.

Test conditions (pH and Temperature) remained within the ranges prescribed by the study plan.

Under ths study conditions, Nectaryl had effects on algae at average measured exposure concentrations of 0.16 mg/L, and, above.
Results with reference substance (positive control):
The results obtained with the Reference substance, Potassium Dichromate following a 72 hour exposure, were, as follows :
72 hour ErC50 = 1.1 mg/L (95% confidence interval 0.71 - 1.7 mg/L)
72 hour EbC50 = 0.59 mg/L (95% confidence interval 0.32 - 1.1 mg/L)
Conclusions:
Under the conditions of the current study, the effect concentrations for Nectaryl with the freshwater algae Selenastrum capricornutum (Pseudo. subcapitata) were :

72 hour Growth Rate End-Points based on measured average exposure concentrations :
ErC50 = 2.9 mg/L
ErC10 = 0.32 mg/L
NOErC = 0.07 mg/L

72 hour Biomass End-Points based on measured average exposure concentrations :
EbC50 = 0.46 mg/L
EbC10 = 0.06 mg/L
NOEbC = 0.07 mg/L
Executive summary:

Under the conditions of the current study, the effect concentrations for Nectaryl with the freshwater algae Selenastrum capricornutum (Pseudo. subcapitata) were :

72 hour Growth Rate End-Points based on measured average exposure concentrations :

ErC50 = 2.9 mg/L

ErC10 = 0.32 mg/L

NOErC = 0.07 mg/L

72 hour Biomass End-Points based on measured average exposure concentrations :

EbC50 = 0.46 mg/L

EbC10 = 0.06 mg/L

NOEbC = 0.07 mg/L

Description of key information

Under the conditions of the current study, the effect concentrations for Nectaryl with the freshwater algae Selenastrum capricornutum (Pseudo. subcapitata) were :

72 hour Growth Rate End-Points based on measured average exposure concentrations :

ErC50 = 2.9 mg/L

ErC10 = 0.32 mg/L

NOErC = 0.07 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
2.9 mg/L
EC10 or NOEC for freshwater algae:
0.32 mg/L

Additional information