Potassium cyanate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

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.