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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:
20 - 25 Mar 1990
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Study is complete, performed under GLP and valid. However no analysis was performed and thus the usability for risk assessment purposes is limited when assessing the bioavailable fraction.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
For the definitive test a stock solution of 1.0 g/L was prepared by dissolving the test substance in deionized water.
This stock solution was titrated to a neutral pH. The selected test concentrations were prepared by dilution of this stock solution in the inoculated test medium. Based on the results of preliminary experiments the definitive test were selected.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
The test was carried out with the unicellular green algae; Selenastrum capricornutum ATCC 22662. This strain was maintained on mineral salts agar slants in the light at room temperature.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Nominal and measured concentrations:
nominal: 2.5, 5.0, 10.0, 20.0 and 40.0 mg/litre
Details on test conditions:
- The KH2PO4 and NaC03 concentrations in the test medium were increased to 160 and 100 mg/litre, respectively, to maintain a constant pH.
- Preliminary experiments to determine the concentration range are performed but not reported according to the guidelines.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
< 2.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
1.34 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: re-calculated
Details on results:
The results of the extinction measurements are presented in in the report. Both the ErC50 and EbC50 (0-72 h) of triethylenetetramine are 20 mg/litre.
The NOEC determined of triethylenetetramime is < 2.5 mg/litre.
Results with reference substance (positive control):
within validity criteria
Reported statistics and error estimates:
according to guideline

EC10 was determined with Toxcalc to be 1.34 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
The toxicity of TETA was tested to S. capricornutum, both EC50 values were determined to be 20 mg/L and the NOEC was <2.5 mg/L. The study meets all criteria and thus is valid. However no analysis was performed and thus the use in risk assessments is restriced.
Executive summary:

The toxicity of triethylenetetramine to exponentially growing S. capricornutum has been assessed over an exposure period of 72 hours, according to the OECD 201 guideline. In the definitive test the algae were exposed to the following nominal concentrations of 2.5, 5.0, 10.0, 20.0 and 40.0 mg/litre. Both the ErC50 (0 -72 h) and EbC50 of triethylenetetramine for S. capricornutum are 20 mg/litre. The NOEC determined of triethylenetetramine is < 2.5 mg/L. The test is valid and meets all criteria. No analysis was performed.

Description of key information

EC50(72 h): 20 mg/L

NOEC (72 h): 1.34 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
20 mg/L
EC10 or NOEC for freshwater algae:
1.34 mg/L

Additional information

The toxicity of the substance to aquatic algae was tested in a guideline study according to OECD 201. The growth of Pseudokirchneriella subcapitata exposed to nominal test substance concentrations of 2.5, 5.0, 10.0, 20.0 and 40.0 mg/L was followed for 72 hours. At the end of the exposure period an EC50(72 h) of 20 mg/L based on the algal growth rate was determined. The recorded NOEC (72 h) was <2.5 mg/L (nominal). An EC10 (72 h) of 1.34 mg/L was re-calculated based on the raw data (software toxcalc v 5.0).