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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:
1959
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
no guideline followed
Principles of method if other than guideline:
No guideline indicated. Principles of method see below.
GLP compliance:
not specified
Analytical monitoring:
not specified
Details on sampling:
not indicated.
Vehicle:
no
Details on test solutions:
Waste water supplemented with 570 mg/L KNO3, 200 mg/L CaSO4, 140 mg/L KH3PO4, 90 mg/L MgSO4 and 3 mg/L FeCl3
Test organisms (species):
Scenedesmus sp.
Details on test organisms:
not indicated.
Test type:
static
Water media type:
freshwater
Total exposure duration:
96 h
Post exposure observation period:
no post exposure period
Hardness:
12°dGH
Test temperature:
24 °C
pH:
7.5
Dissolved oxygen:
not indicated.
Salinity:
not indicated.
Nominal and measured concentrations:
not indicated.
Details on test conditions:
not indicated.
Reference substance (positive control):
yes
Remarks:
known water pollutants were measured in parallel
Key result
Duration:
96 h
Dose descriptor:
LOEC
Effect conc.:
520 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
not indicated.
Results with reference substance (positive control):
not indicated.
Reported statistics and error estimates:
not indicated.
Validity criteria fulfilled:
not specified
Conclusions:
Potassium cyanate showed toxicity on growth of Scenedesmus sp. from a concentration of from 520 mg/L on.
Executive summary:

In a 96 hour acute toxicity study, the cultures of Scenedesmus sp. were exposed to potassium cyanate under static conditions. Potassium cyanate showed a distinct toxicity on growth of Scenedesmus sp. from a concentration of 520 mg/L on (LOEC = 520 mg/L). This toxicity study is classified as acceptable as key study.


Results Synopsis:


Test Organism: Scenedesmus sp.


Test Type: Static


LOEC = 520 mg/L

Description of key information

For potassium cyanate, a non-standard study (key) is available. The LOEC identified was 520 mg/L in Scenedesmus sp. In a read-across study (supporting) with the structural analogue sodium cyanate, which was conducted recently according to OECD and EU Guidelines and GLP, a LC50 of >100 mg/L, equivalent to > 125 mgL of potassium cyanate, was determined in a limit study in Desmodesmus subspicatus.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
520 mg/L

Additional information

Key Study:

In a 96 hour acute toxicity study, the cultures of Scenedesmus sp. were exposed to potassium cyanate under static conditions. Potassium cyanate showed a distinct toxicity on growth of Scenedesmus sp. from a concentration of 520 mg/L on (LOEC = 520 mg/L).

Supporting study:

The study (LAUS, 2009) was performed using one concentration containing 100 mg/L. The treatments were used to incubate the unicellular freshwater green alga Desmodesmus subspicatus for a period of 72 hours. The cell concentration of each replicate was determined by measuring the absorption of the cuvettes at 440 nm every 24 hours with a spectral photometer. With these measured values, the number of cells was calculated (linear correlation be-tween cell concentration and absorption given). Then the growth rate µ, the area under the growth curve (AUC ) and the Yield were determined.

At the beginning and at the end of the test, the content of the test item in the test solution was determined using a spectral photometer. The recovery after 72 hours was 109 % of the start concentration. The correlation between nominal and measured concentration was good (98% at the beginning.and.107 % at the end). Therefore, the determination of the biological results was based on nominal concentration.

The EC50s of potassium dichromate were tested in a current positive control test. The values lay within the normal range of the laboratory.

The following results for the test item sodium cyanate were determined:

Endpoint

NOEC

LOEC

EC50

Growth Rate

100 mg/L

>100 mg/L

>100 mg/L

AUC

100 mg/L

>100 mg/L

>100 mg/L

Yield

100 mg/L

>100 mg/L

>100 mg/L

The NOEC value of 100 mg/L for sodium cyanate corresponds to a value of 125 mg/L potassium cyanate and supports the LOEC value of > 520 mg/L as described in the key study.

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