Potassium bromate

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-04-23 to 2010-04-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

The study was performed in compliance with the Good Laboratory Practice (GLP) regulations (revised in 1997, ENV/MC/CHEM(98)17). The method followed that described in the OECD Guidelines for Testing of Chemicals (Adopted: 4 April 1984) No 201 "Alga, Growth Inhibition Test", adopted March 23, 2006.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Principles of method if other than guideline:

None

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Potassium bromate

EC Number:

231-829-8

EC Name:

Potassium bromate

Cas Number:

7758-01-2

Molecular formula:

BrHO3.K

IUPAC Name:

potassium bromate

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
all test concentrations and the control

- Sampling method:
Samples were taken at the beginning of the study and after 72 hours. The samples were delivered to the analytic laboratory for a quantitative analysis.

- Sample storage conditions before analysis:
All samples were stored in a refrigerator immediately after sampling and were kept stored to enable additional analyses.

Test solutions

Vehicle:

yes

Details on test solutions:

The test medium (reconstituted water and test material) was freshly prepared. The calibrated flask with test material and vehicle, reconstituted water, was treated in an ultrasound bath for 1 hour. Subsequently, the preparation was stirred with a magnetic stirrer for further 23 hours. Afterwards, the preparation was filtered through a filter funnel with a pore size of 10-16 µm. The filtrate was used for the study.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The test system used for this study was a green unicellular algae species, Desmodesmus subspicatus, strain No. SAG 86.81, supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universitat Gottingen". This strain is recommended by international guidelines.

Study design

Test type:

static

Water media type:

not specified

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

250 mg CaCO3

Test temperature:

22-23 °C

pH:

8.3±0.4

Dissolved oxygen:

about 80 %

Salinity:

for details see composition of reconstituted water "details on test conditions"

Nominal and measured concentrations:

The study was performed with nominal concentrations of 10.0, 17.8, 31.6, 56.2 and 100.0 mg/L in reconstituted water.

Details on test conditions:

The test medium (reconstituted water and test material) was freshly prepared. The light intensity was approximately 7500 to 9500 Lux. The experimental part was started by inoculation of algae to the different groups so that the flasks contained about 10,000 cells/mL. The algae were taken from an exponentially growing pre-culture (growth rate 120.7) which was set up 3 days prior to the experimental part under the same conditions as in the final study.

Details on composition of the reconstituted water:

Macro-nutrients:
50.00 mg/L NaHCO3
18.00 mg/L CaCl2 x 2 H2O
15.00 mg/L NH4Cl
15.00 mg/L MgSO4 x 7 H2O
12.00 mg/L MgCl2 x 6 H2O
1.60 mg/L KH2PO4

Trace elements:
100.00 µg/L Na2EDTA x 2 H2O
64.00 µg/L FeCl3 x 6 H2O
415.00 µg/L MnCl2 x 4 H2O
185.00 µg/L H3BO3
7.00 µg/L Na2MoO4 x 2 H2O
3.00 µg/L ZnCl2
1.50 µg/L CoCl2 x 6 H2O
0.01 µg/L CuCl2 x 2 H2O

The pH of the reconstituted water after aeration is approximately 8.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

31.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

56.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

for details see executive summary

Results with reference substance (positive control):

Regularly, a positive control test to check the test system is carried out with potassium dichromate.

Reported statistics and error estimates:

For the determination of the LOEC and NOEC, average growth rate and yield at the test concentrations were compared to the control values by Williams tests.

Any other information on results incl. tables

The following nominal and mean analytical concentrations were obtained at time points as indicated:

Nominal Concentration in [mg/L]	Mean Analytical Concentration in [mg/L]
	0 hours	72 hours
100.0	99.9	101.9
56.2	56.3	57.3
31.6	31.3	32.6
17.8	17.5	17.9
10.0	9.9	10.1

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Under the given conditions of this study the 72h EC50 value was 603.5 (189.3 – n.d.) mg/L for Yield. The EC50 value for the Growth rate could not be determined.

Executive summary:

Purpose
The purpose of this assay was to identify the aquatic toxicity potential of potassium bromate in algea to provide a rational basis for hazard estimation for the test item in aquatic environments.

Study Design
The influence of the test material on the growth and growth rate of the green algae species Desmodesmus subspicatus was tested. The algae were exposed to different concentrations of the test material and the growth was calculated after 24, 48, or 72 hours of exposure in the test media. The study was performed with nominal concentrations of 10.0, 17.8, 31.6, 56.2 and 100.0 mg/L in reconstituted water. The study design included one control with six replicates and five test material groups with three replicates, each containing 100 mL reconstituted water or test medium and about 10,000 cells/mL at the start of the experimental phase. The study was performed in an open static test system.
The test material concentrations were analyzed at 0 (start) and 72 hours after start of the experimental part.


Results

The limit of detection of the analytical method was 0.07 mg/L. The analytically determined concentrations were between 98.3 – 100.2 % at the start and 100.6 – 103.2 % at the end of the experimental part.

For the test material the following EC values, low effect and no effect concentration for Desmodesmus subspicatus were determined:

Parameter (0-72h)	Growth rate	Yield
EC10 (mg/L) 95% confidence interval	n.d n.d.	43.9 0.2 – 77.8
EC20 (mg/L) 95% confidence interval	n.d. n.d.	>100 63.0 – 258728.2
EC50 (mg/L) 95% confidence interval	>100 n.d.	>100 n.d.
NOEC (mg/L)	31.6	31.6
LOEC (mg/L)	56.2	56.2

n.d.   could not be determined

Conclusion
Under the given conditions of this study the 72h EC50 values for Yield and Growth rate could not be determined as it exceeds the limit concentration of 100 mg/L.