Potassium chlorate

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
[further information is included as attachment to Iuclid section 13]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that the common compound ClO3- is solely responsible for the effects encountered, because the source and the target substance were transformed (by dissociation) into chlorate-ion (ClO3-).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Refer to the Test material section of the source and target records.

3. ANALOGUE APPROACH JUSTIFICATION
See attached document in Iuclid section 13

4. DATA MATRIX
See attached document in Iuclid section 13

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

GLP compliance:

yes

Details on sampling:

.

Key result

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

11.5 mg/L

Remarks on result:

other: potassium chlorate

Duration:

7 d

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: sodium chlorate

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

134 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: 33.7- > 320 mg/L

Details on results:

Details on results
Biomass growth (number of fronds):
EC50 = 73.7 mg/L (95% c.i. 34.5-158 mg/L)
LOEC = 32 mg/L NOEC = 10 mg/L
Growth rate (number of fronds):
EC50 = 134 mg/L (95% c.i. 33.7- > 320 mg/L)
LOEC = 32 mg/L NOEC = 10 mg/L
Biomass dry weight:
EC50 = 128 mg/L (95% c.i. 28.0- > 320 mg/L)
LOEC = 32 mg/L
NOEC = 10 mg/L
- Evaluation after day 7 (mean and standard deviation in brackets):

Conc (mg/L) log biomass Inhibition of
integral log biomass (%)
control 7.49 (0.49)
3.2 8.37 (0.29) -11.74 (3.88)
10 8.30 (0.29) -10.75 (3.82)
32 6.12 (0.44) 18.31 (5.81)
100 3.25 (0.47) 56.58 (6.27)
320 0.24 (0.11) 96.83 (1.50)

Conc (mg/L) Specific Inhibition of
growth rate specific growth rate (%)

control 0.350 (0.020)
3.2 0.366 (0.020) -4.45 (5.08)
10 0.355 (0.000) -1.44 (1.31)
32 0.289 (0.010) 17.29 (3.15)
100 0.204 (0.010) 41.74 (2.04)
320 0.099 (0.20) 71.70 (6.18)

Conc (mg/L) Doubling Biomass dw Inhibition of
time of (mg) biomass dw (%)
fronds (d)

control 1.98 (0.12) 26.0 (2.1)
3.2 1.90 (0.09) 29.5 (0.6) -4.87 (0.79)
10 1.95 (0.03) 23.4 (0.9) 4.21 (1.52)
32 2.39 (0.09) 15.4 (2.0) 20.37 (4.95)
100 3.40 (0.12) 8.4 (0.6) 43.92 (2.81)
320 7.00 (1.86) 4.2 (0.6) 70.78 (5.41)

- Other observations: In the three highest concentrations the fronds were lighter green and partly covered with white spots at day 2.
At day 5 the fronts in 320 and 100 mg/L were partly without pigmentation and in 32 mg/L fronds were partly covered with white spots.
At day 7 fronds in the three highest concentrations were partly without pigmentation.

Validity criteria fulfilled:

yes

Conclusions:

Test conducted under GLP with analysis, analysis certificate and to relevant guideline. This study can be considered reliable without restrictions.
The NOEC based on biomass dry weight is 10 mg/l. The lowest EC50 is based on biomass grwoth and is 73.7 mg/L (95% c.i. 34.5-158 mg/L).

Executive summary:

 

The effects of the test item Sodium Chlorate on growth of the monocotyledon species Lemna minor were determined according to the principles of OECD-Guideline 221 (Revised Draft Document July 2002), from October 29 to November 05, 2003 at DR.U.NoACK-LABORATORIEN, Sarstedt, Germany. The test item (batch number 1E01 03WF) contained 99.66 % Sodium Chlorate. The aim of the study was to determine the effects of the test item on the growth of Lemna minor over 7 days under static exposure conditions. On the basis of a preliminary test, 5 concentration levels were chosen in a geometrical series with a dilution factor of √1 0: nominal: 3.2 - 10 - 32 - 100 - 320 mg/L. Three replicates were investigated for the test concentrations and the control. Frond numbers were assessed on days 0, 2, 5 and 7. Inhibition of log biomass growth. specific growth rate and biomass dry weight were determined. The concentrations of sodium chlorate were analysed on day 0 (freshly prepared solutions) and on day 7 (old solutions) via HPLC. The recovery rates of the active ingredient chlorate were> 80 % at start and end of the study (for details of the analytical method and results please refer to chapter 10). Environmental parameters like water temperature and pH-value were determined to be within the acceptable limits. The effects of sodium chlorate, based on nominal concentrations, are summarised in table 1.   Table 1: Effects on Lemna minor after 2, 5 and 7 d (based on nominal concentrations of the test item)      2d 5d  7d    Inhibition of log biomass growth [mg/L]          Elog bC50value  91.3 60.5 73.7  95 % confidence interval for ElogbC50values  68.6 -122  38.6 -95.0   34.5 -158  LOEC 100 100  32   NOEC 32  32  10  Inhibition of specific growth rate [mg/L]            ErC50value  91.3  57.8  134  95 % confidence interval for ErC50values  68.6 -122 35.8 -93.3  33.7 - >320   LOEC 100  100  32   NOEC 32  32  10  Inhibition of log biomass dry weight [mg/L]            ElogdwC50value n.a  n.a  128   95% cofidence interval forElogdwC50value n.a  n.a  28.0- >320   LOEC n.a  n.a  32   NOEC n.a  n.a  10  n.a. =not applicable

Based on read-across approach, it can be concluded that the result of the aquatic plant study conducted with the source substance is likely to predict the properties of the target substance with a NOEC growth (7d) of 11.5 mg/L based on molecular weight of potassium chlorate.

Reference 2

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study generated according to generally valid and internationally accepted testing guideline and performed under GLP.

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 221 (revised draft document 2002)

Deviations:

yes

Remarks:

Swedish Standard (SIS) medium. Modified: NH4Cl was given as inorganic nitrogen source instead of NaNO3 to get sufficient recovery rates of concentration control analysis. growth sp. inhibition test"

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

At the start and the end of the test samples were taken for analyses.

Vehicle:

no

Details on test solutions:

- Dispersion treatment: Agitation
- Procedures: 320 mg/L prepared with dilution water

Test organisms (species):

Lemna minor

Details on test organisms:

- Source/supplier: OekoTox Moser & Pickl Gbr, Stuttgart, Germany
- Laboratory culture: yes
- Method of cultivation: in 900 ml crystallization dishes, filled with 500 ml Swedish Standard (SIS) Medium.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Test temperature:

24 ± 1 °C

pH:

6.60-6.64 at the start of the test and 5.23-5.95 at the end

Nominal and measured concentrations:

- Nominal test concentrations: 0.0, 3.2, 10, 32, 100, 320 mg/L
- The measured concentrations of the test substance were between 90 and 107% of the nominal concentrations, therefore the nominal values were
used for the calculations

Details on test conditions:

Swedish Standard (SIS) medium, modified GROWTH/TEST MEDIUM CHEMISTRY: Swedish Standard (SIS) medium
- pH: 6.5 ± 0.2
- Exposure vessel type: Crystallization dishes with a volume of 500 ml, covered with glass tops and filled with 200 ml test solution.
- Number of replicates, plants per replicate: 3, 3 plants with 4 fronds each
- Intensity of irradiation: 6500-10000 lx (85-125 µmol/m2*s)
- Photoperiod: continuous fluorescent light
- Number of plants (start and end of the test), number of fronds (on day 0, 2, 5 and 7) and dry weight (at the end of the test).
On each observation day the pigmentation, destruction of roots etc. were determined.

Reference substance (positive control):

yes

Remarks:

Zinc chloride, 99.2% pure

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

134 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks on result:

other: 33.7- > 320 mg/L

Details on results:

Details on results
Biomass growth (number of fronds):
EC50 = 73.7 mg/L (95% c.i. 34.5-158 mg/L)
LOEC = 32 mg/L NOEC = 10 mg/L
Growth rate (number of fronds):
EC50 = 134 mg/L (95% c.i. 33.7- > 320 mg/L)
LOEC = 32 mg/L NOEC = 10 mg/L
Biomass dry weight:
EC50 = 128 mg/L (95% c.i. 28.0- > 320 mg/L)
LOEC = 32 mg/L
NOEC = 10 mg/L
- Evaluation after day 7 (mean and standard deviation in brackets):

Conc (mg/L) log biomass Inhibition of
integral log biomass (%)
control 7.49 (0.49)
3.2 8.37 (0.29) -11.74 (3.88)
10 8.30 (0.29) -10.75 (3.82)
32 6.12 (0.44) 18.31 (5.81)
100 3.25 (0.47) 56.58 (6.27)
320 0.24 (0.11) 96.83 (1.50)

Conc (mg/L) Specific Inhibition of
growth rate specific growth rate (%)

control 0.350 (0.020)
3.2 0.366 (0.020) -4.45 (5.08)
10 0.355 (0.000) -1.44 (1.31)
32 0.289 (0.010) 17.29 (3.15)
100 0.204 (0.010) 41.74 (2.04)
320 0.099 (0.20) 71.70 (6.18)

Conc (mg/L) Doubling Biomass dw Inhibition of
time of (mg) biomass dw (%)
fronds (d)

control 1.98 (0.12) 26.0 (2.1)
3.2 1.90 (0.09) 29.5 (0.6) -4.87 (0.79)
10 1.95 (0.03) 23.4 (0.9) 4.21 (1.52)
32 2.39 (0.09) 15.4 (2.0) 20.37 (4.95)
100 3.40 (0.12) 8.4 (0.6) 43.92 (2.81)
320 7.00 (1.86) 4.2 (0.6) 70.78 (5.41)

- Other observations: In the three highest concentrations the fronds were lighter green and partly covered with white spots at day 2.
At day 5 the fronts in 320 and 100 mg/L were partly without pigmentation and in 32 mg/L fronds were partly covered with white spots.
At day 7 fronds in the three highest concentrations were partly without pigmentation.

Results with reference substance (positive control):

- Concentrations: 0.0, 0.32, 1, 3.2, 10, 32 mg/L
- Results:
- EC50 (biomass growth) = 9.5 mg/L (95% c.i. 1.8-50.2 mg/L)
- EC50 (growth rate) = 5.2 mg/L (95% c.i. 1.1-24.6 mg/L)
- EC50 (biomass dry weight) = 10.9 mg/L (95% c.i. 3.2-37.1 mg/L)

Reported statistics and error estimates:

ANOVA and Dunnett's test were used for determination of significant differences compared control replicates.
If normality of equal variance failed Bonferroni t-test was carried out. Probit analysis for calculation of EC50, confidence intervals
are calculated using.

Validity criteria fulfilled:

yes

Conclusions:

Test conducted under GLP with analysis, analysis certificate and to relevant guideline. This study can be considered reliable without restrictions.
The NOEC based on biomass dry weight is 10 mg/l. The lowest EC50 is based on biomass grwoth and is 73.7 mg/L (95% c.i. 34.5-158 mg/L).

Executive summary:

The effects of the test item Sodium Chlorate on growth of the monocotyledon species Lemna minor were determined according to the principles of OECD-Guideline 221 (Revised Draft Document July 2002), from October 29 to November 05, 2003 at DR.U.NoACK-LABORATORIEN, Sarstedt, Germany. The test item (batch number 1E01 03WF) contained 99.66 % Sodium Chlorate. The aim of the study was to determine the effects of the test item on the growth of Lemna minor over 7 days under static exposure conditions. On the basis of a preliminary test, 5 concentration levels were chosen in a geometrical series with a dilution factor of √1 0: nominal: 3.2 - 10 - 32 - 100 - 320 mg/L. Three replicates were investigated for the test concentrations and the control. Frond numbers were assessed on days 0, 2, 5 and 7. Inhibition of log biomass growth. specific growth rate and biomass dry weight were determined. The concentrations of sodium chlorate were analysed on day 0 (freshly prepared solutions) and on day 7 (old solutions) via HPLC. The recovery rates of the active ingredient chlorate were> 80 % at start and end of the study (for details of the analytical method and results please refer to chapter 10). Environmental parameters like water temperature and pH-value were determined to be within the acceptable limits. The effects of sodium chlorate, based on nominal concentrations, are summarised in table 1. Table 1: Effects on Lemna minor after 2, 5 and 7 d (based on nominal concentrations of the test item)    2d 5d  7d    Inhibition of log biomass growth [mg/L]          Elog bC50value  91.3 60.5 73.7  95 % confidence interval for ElogbC50values  68.6 -122  38.6 -95.0   34.5 -158  LOEC 100 100  32   NOEC 32  32  10  Inhibition of specific growth rate [mg/L]            ErC50value  91.3  57.8  134  95 % confidence interval for ErC50values  68.6 -122 35.8 -93.3  33.7 - >320   LOEC 100  100  32   NOEC 32  32  10  Inhibition of log biomass dry weight [mg/L]            ElogdwC50value n.a  n.a  128   95% cofidence interval forElogdwC50value n.a  n.a  28.0- >320   LOEC n.a  n.a  32   NOEC n.a  n.a  10  n.a. =not applicable

Description of key information

The NOEC for fresh water aquatic plants is 10 mg/l sodium chlorate. On a molecular weight basis this would be 11.5 mg/l potassium chlorate.

Key value for chemical safety assessment

EC10 or NOEC for freshwater plants:

11.5 mg/L

Additional information

No studies are available on potassium chlorate.

One valid study was found with sodium chlorate for lemna minor. The NOEC for fresh water aquatic plants is 10 mg/l sodium chlorate. On a molecular weight basis this would be 11.5 mg/l potassium chlorate.

Lemna minor is the most sensitive freshwater species tested to sodium chlorate.