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Ecotoxicological information

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:
22-26 March 1979
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP status not known, available as unpublished report, predates OECD study guidelines but otherwise acceptable for assessment. There was no information test solution preparation or observational data on the test substance behaviour which from tests on similar substances indicates that globules formed during the study. Therefore this study is used but major reservations.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
US EPA Algal Assay Procedure: Bottle Test. 1971.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
not specified
Details on sampling:
No data
Vehicle:
no
Details on test solutions:
Concentrations for the definitive test were based on the results of a 96-hour range-finding test. Test concentrations were prepared by adding appropriate weighed amounts of test material directly to each flask. Concentrations are reported as mg of test material per litre of algal growth medium or ppm.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Obtained from the USEPA's Environmental Research Laboratory, Corvallis, Oregon. Maintained in stock culture at BMRL.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Post exposure observation period:
none reported
Hardness:
no data reported
Test temperature:
24°C ±1°C
pH:
ranged from 7.2 to 7.4
Dissolved oxygen:
no data reported
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal. 3 replicates for each of the 3 concentrations (360, 600 and 1000 mg/l), plus 3 replicates for the control.
Details on test conditions:
125 ml flask. '~20,000 cells per ml. ~4000 lux.
Reference substance (positive control):
no
Key result
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 other: ppm
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Key result
Duration:
96 h
Dose descriptor:
EC10
Effect conc.:
>= 360 - <= 600 other: ppm
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Details on results:
After 96 hours of exposure, decrease of in vivo chlorophyll α was from 22% in cultures exposed to 360 and 600 ppm to 36% in those exposed to 1000 ppm. Decrease of cell numbers was from 9% in cultures exposed to 360 ppm to 21% in those exposed to 1000 ppm.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Probit analysis.

Nominal        chg    % chg 
concentration  pH      Chlor  alpha    Cell no. 
mg/l;ppm  0 h  96 h  24 h  48 h  72 h  96 h  96 h 
Control  7.2  7.4  ---  ---  ---  ---  --- 
360  7.2  7.3  -7  -17  -36  -22  -9 
600  7.2  7.3  -13  -27  -40  -22  -12 
1000  7.2  7.2  -9  -26  -47  -36  -21 
Conclusions:
The estimated 24-, 48-, 72-, and 96-hour EC50s were >1000 ppm. The 96-hour EC50 based on cell number decrease was also >1000 ppm. The EC10 (cell number) can be estimated as being in the range of 360 to 600 ppm. The table of results shows some effects but concentrations were far in excess of the water solubility of the substance. It is therefore concluded that Santicizer 278 is non-toxic to algae.
Executive summary:

This laboratory study was conducted before current OECD guidelines came into effect, although it was conducted in accordance with U.S. guidelines of the time (1979) and is considered adequate for assessment. It is considered reliable with restrictions. The estimated 24-, 48-, 72-, and 96-hour EC50s were >1000 ppm.  The 96-hour EC50 based on cell number decrease was also >1000 ppm. The EC10 (cell number) can be estimated as being in the range of 360 to 600 ppm.  The table of results shows some effects but concentrations were far in excess of the water solubility of the substance. It is therefore concluded that Santicizer 278 is non-toxic to algae.

Description of key information

The 96-hour EC50 based on both cell number decrease and growth rate was >1000 mg/l.  The EC10 (cell number) can be estimated as being in the range of 360 to 600 ppm. This exceeds the solubility of the test compound (0.0015 mg/l at 25°C) and it is therefore concluded that Santicizer 278 is non-toxic to algae.

Key value for chemical safety assessment

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