Sodium cyanate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2012-03-23 to 2012-04-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.20 (Daphnia magna Reproduction Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1300 (Daphnid Chronic Toxicity Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Sampling method:
Calibration solutions for sodium cyanate: Stock solution (~1 mg/mL): ~10 mg of the test item was dissolved in water to a total volume of 10 mL. 6 calibration solutions were diluted with water: 0.1, 0.2, 0.5, 1, 2, and 5 µg/mL.
Sample preparation for the analysis:
The samples were measured directly, after the reaction of cyanate ions with 2-aminobenzoic acid. The pH value of the samples was adjusted to ~pH 4.5 with buffer solution. 2-aminobenzoic acid and hydrochloric acid solution were added and the solution was thermostated. The absorbance of this reaction compound in the hydrochloric acid solution was measured at a wavelength of 310 nm.

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: Laboratory of Hydrobiology (Central Agricultural Office, Directorate of Plant-, and Soil Protection) 2100 Gödöllő, Kotlán S. u. 3. Hungary
- Age of parental stock (mean and range, SD):
- Feeding during test: yes
- Amount: 0.15 mg C/Daphnia/day
- Frequency: daily

ACCLIMATION
- Acclimation period: Brood daphnids were maintained in Elendt M4 Medium under test conditions for about 21 days prior to the start of the test.
The stock animals were maintained under test conditions (light, temperature, medium, feeding and animals per unit volume) to avoid the necessity of longer adaptation prior to the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 h

Hardness:

218.9 – 254.5 mg/L

Test temperature:

20.0 – 20.9°C in the control
20.0 – 20.8°C in the 0.8 mg/L concentration

pH:

pH 7.86 to 8.64 in the control
pH 7.88 to 8.29 in the 0.8 mg/L concentration

Dissolved oxygen:

7.68 to 9.51 mg/L in the control
7.23 to 8.92 mg/L in the 0.8 mg/L concentration

Nominal and measured concentrations:

0.025; 0.05; 0.1; 0.2; 0.4, and 0.8 mg/L (nominal concentrations)
The test item concentrations were measured in the range from 94 % to 109 % of the nominal values at the start of the measured renewal period and from 94 % to 117% of the nominal values at the end of the renewal period.

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers (100 mL volume) with 80 mL test medium
- Renewal rate of test solution: 3 days
- No. of organisms per vessel: one per vessel
- No. of vessels per concentration: ten replicates
- No. of vessels per control: ten replicates

TEST MEDIUM / WATER PARAMETERS
- in accordance to the guildeline

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: 16 h light : 8 h dark
- Light intensity: appropx. 1292 lux that corresponds to 17.46 µE m-2s-1

EFFECT PARAMETERS MEASURED: mortality, offspring

VEHICLE CONTROL PERFORMED: no vehicle used

RANGE-FINDING STUDY
- Test concentrations: Two non-GLP preliminary range-finding tests were performed. In the first range-finding test the examined nominal concentrations were: 1, 2.5; 5, 10, 25; 50 and 100 mg test item/L. In the second range-finding test the following concentration range was investigated: 0.125; 0.25; 0.5; 0.7 and 0.9 mg test item/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.05 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

0.81 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

- Mortality of parent animals: In the performed chronic toxicity test 10 % mortality was observed at the lowest concentration of 0.025 mg/L. This mortality was within the assay acceptance range of the control, therefore the observed mortality was not evaluated as an effect of the test item.
- Time to first brood release or time to hatch: the first brood appeared in every of the concentrations on days 8-10 of the test.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: The 24-hour EC50 of Potassium dichromate: 0.97 mg/L. The 24-h NOEC: 0.50 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

In the 21-day semi-static chronic toxicity test to Daphnia magna with sodium cyanate the 21-day EC50 value was calculated to be 0.81 mg test item/L. The NOEC value was determined as 0.05 mg test item/L, consequently the LOEC was 0.1 mg test item/L.

Executive summary:

The purpose of this study was to evaluate the influence of the test item sodium cyanate on the reproductive output of Daphnia magna in a semi-static test system. Young female Daphnia (the parent animals) aged less than 24 hours at the start of the test were exposed to aqueous test media containing the test item for 21 days at a range of concentrations. The nominal test item concentrations were 0.025; 0.05; 0.1; 0.2; 0.4 and 0.8 mg test item/L. As the parallel running analytical determinations showed that the test item concentrations remained within the range of ±20 % of the nominal and of the initial concentrations (varied between 94 and 117 percent of the nominal concentration); therefore all of the results are based on the nominal test item concentrations. The reproduction of the parent animals at the test item concentrations of 0.1; 0.2; 0.4 and 0.8 mg/L was statistically significant different from that of the control group after the exposure period of 21 days in the chronic toxicity test. The LOEC was 0.1 mg test item/L. The NOEC was determined as 0.05 mg test item/L, as this test concentration - immediately below the LOEC - has no statistically significant effect (p < 0.05) when compared to the control, within a stated exposure period of 21 days. The observed reduction was 9.09 % at the test item concentration of 0.025 mg/L. In the group of 0.05 mg/L the percentage reduction was 17.46 %. In the test item treatment group of 0.1 mg/L the observed reduction in reproduction was 26.00 %, while at the concentrations of 0.2 mg/L and 0.4 mg/L it was calculated as 29.35 and 35.89 %, respectively. At the highest test item concentration of 0.8 mg/L 53.59 % reduction of reproduction was calculated after 21 days. On the basis of these results the EC50 of the test item was calculated to be 0.81 mg test item/L. In the performed chronic toxicity test 10 % mortality was observed at the lowest test item concentration of 0.025 mg/L. This mortality was within the assay acceptance range of the control, therefore the observed mortality was not evaluated as an effect of the test item. The body length values measured at the end of the test showed statistically significant differences compared to the control in both of the treatment groups of 0.4 and 0.8 mg/L.

Description of key information

In the 21-day semi-static chronic toxicity test to Daphnia magna with sodium cyanate the 21-day EC50 value was calculated to be 0.81 mg test item/L. The NOEC value was determined as 0.05 mg test item/L, consequently the LOEC was 0.1 mg test item/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.05 mg/L

Additional information

The purpose of this study was to evaluate the influence of the test item sodium cyanate on the reproductive output of Daphnia magna in a semi-static test system in accordance with OECD guideline 211, EU method C.20 and OPPTS 850.1300 guideline. Young female Daphnia (the parent animals) aged less than 24 hours at the start of the test were exposed to aqueous test media containing the test item for 21 days at a range of concentrations. The nominal test item concentrations were 0.025; 0.05; 0.1; 0.2; 0.4 and 0.8 mg test item/L. As the parallel running analytical determinations showed that the test item concentrations remained within the range of ±20 % of the nominal and of the initial concentrations (varied between 94 and 117 percent of the nominal concentration); therefore all of the results are based on the nominal test item concentrations. The reproduction of the parent animals at the test item concentrations of 0.1; 0.2; 0.4 and 0.8 mg/L was statistically significant different from that of the control group after the exposure period of 21 days in the chronic toxicity test. The LOEC was 0.1 mg test item/L. The NOEC was determined as 0.05 mg test item/L, as this test concentration - immediately below the LOEC - has no statistically significant effect (p < 0.05) when compared to the control, within a stated exposure period of 21 days. The observed reduction was 9.09 % at the test item concentration of 0.025 mg/L. In the group of 0.05 mg/L the percentage reduction was 17.46 %. In the test item treatment group of 0.1 mg/L the observed reduction in reproduction was 26.00 %, while at the concentrations of 0.2 mg/L and 0.4 mg/L it was calculated as 29.35 and 35.89 %, respectively. At the highest test item concentration of 0.8 mg/L 53.59 % reduction of reproduction was calculated after 21 days. On the basis of these results the EC50 of the test item was calculated to be 0.81 mg test item/L. In the performed chronic toxicity test 10 % mortality was observed at the lowest test item concentration of 0.025 mg/L. This mortality was within the assay acceptance range of the control, therefore the observed mortality was not evaluated as an effect of the test item. The body length values measured at the end of the test showed statistically significant differences compared to the control in both of the treatment groups of 0.4 and 0.8 mg/L.