Permanganic acid

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:

20.October - 23. October 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

23.03.2006, Annex 5 corrected: 28 July 2011

Deviations:

yes

Remarks:

The pre-culture was prepared 5 days before the test start. As all validity criteria were met and exponential growth was observed in the blank control this was stated as uncritical.

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: SAG strain number 86.81
- Source (laboratory, culture collection): MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen), May 2020
- Age of inoculum (at test initiation):
- Method of cultivation: stock culture on solid agar at 2 - 8 °C

ACCLIMATION
- Acclimation period: pre-culture: nutrient medium and incubated under continuous lighting for 4 days under test conditions (Lighting: within the specified range of 4440 – 8880 lux; 21.7 – 22.5 °C)
- Culturing media and conditions (same as test or not): standard algal medium
- Any deformed or abnormal cells observed:

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21.6 – 22.3 °C

pH:

7.7 - 7.9

Nominal and measured concentrations:

nominal: 100, 32, 10, 3.2, 1 mg/L (related to test item)
calculated (by dilution factor from highest conctration measured at start): 3.11, 0.97, 0.30, 0.09, 0.03 (related to permanganic acid)

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks total volume 65 mL
- Type (delete if not applicable): open (covered with perforated plastic foil acting as a stopper)
- Material, size, headspace, fill volume: glasss, headspace: 20 mL., fill volume: 45 ± 1 mL
- Aeration:
- Type of flow-through (e.g. peristaltic or proportional diluter): -
- Renewal rate of test solution (frequency/flow rate): -
- Initial cells density: 2.4x10^3
- Control end cells density: 5.2x10^5
- No. of organisms per vessel: -
- No. of vessels per concentration (replicates): 3 vessels, each filled with 45 ±1 mL test solution and algae; 1 vessel, filled with 45 ±1 mL test solution without algae for analytical determination
- No. of vessels per control (replicates):6 vessels, each filled with 45 ±1 mL algal medium and algae; 1 vessel filled with 45 ±1 mL algal medium without algae for analytical determination
- No. of vessels per vehicle control (replicates):-

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used: -

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: demin water
- Total organic carbon: -
- Particulate matter: -
- Metals: -
- Pesticides: -
- Chlorine: -
- Alkalinity: -
- Ca/mg ratio: -
- Conductivity: -
- Culture medium different from test medium: no
- Intervals of water quality measurement: -

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: -
- Photoperiod: continuous
- Light intensity and quality: 4440 – 8880 Lux
- Salinity (for marine algae): -

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [electronic particle counter] Cell Counter Z2, Beckman Coulter
- Chlorophyll measurement:-
- Other: -

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations: not stated
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (K2Cr2O7, CAS No. 7778-50-9)

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.07 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

HMnO4

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.35 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

HMnO4

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

< 0.03 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

HMnO4

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

<= 0.03 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Remarks:

HMnO4

Basis for effect:

growth rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50: growth rate 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L
- Other:

Reported statistics and error estimates:

Statistics were calculated with ToxRat Professional (V.3.3.0). Confidence intervals were calculated. 72h ErC10 0.05 mg/L – 0.10 mg/L, 72h ErC50 0.23 mg/L – 0.55 mg/L

 

Growth Rate µ, Yield

Nominal Concentration in mg/L	Parameter	Growth Rate (0-72 h) [day^-1]	Yield (0-72 h) [Cell Concentration/mL]
Blank control	Mean	1.78	518207
	SD	0.06	91005
1	Mean	1.69	381827
	SD	0.02	19976
3.2	Mean	1.58	278573
	SD	0.05	38685
10	Mean	0.82	25907
	SD	0.05	4042
32	Mean	0.35	4633
	SD	0.04	976
100	Mean	0.18	1780
	SD	0.01	144

SD = Standard Deviation

 

Inhibition Values

Nominal concentration in mg/L	% Inhibition
	Growth Rate (0-72 h)	Yield (0-72 h)
Blank control	0	0
1	5.4	26.3
3.2	11.4	46.2
10	54.3	95.0
32	80.2	99.1
100	89.8	99.7

 

Daily Growth Rates of the blank controls

Growth rates	days 0 – 1	days 1 – 2	days 2 – 3	CV of sectional daily growth rates	days 0 – 3
Replicate 1	2.162	1.683	1.178	29 %	1.674
Replicate 2	2.165	1.905	1.172	29 %	1.747
Replicate 3	2.160	1.871	1.418	21 %	1.816
Replicate 4	2.475	1.700	1.189	36 %	1.788
Replicate 5	2.548	1.590	1.367	34 %	1.835
Replicate 6	2.222	1.318	1.970	25 %	1.837
Mean	2.289	1.678	1.382	29 %	1.783
Standard deviation	0.176	0.213	0.307		0.063
CV	8 %	13 %	22 %		4 %

 

 

Assessment

Parameter	Validity criteria	Observed value	Assessment
Increase factor biomass	factor 16 in 72 h	213	Valid
Mean coefficient of variation of daily growth rates	max. 35 %	29 %	Valid
Coefficient of variation of average growth rate during the whole test period	max. 7 %	4 %	Valid

 

Validity criteria fulfilled:

yes

Conclusions:

An effect concentration EC50 (72 h) of 0.35 mg/L (95% c.i. 0.23 – 0.55 mg/L) was determined in this study.

Executive summary:

One valid experiment was performed.

The study was performed using 5 concentrations ranging from 1 to 100 mg/L (nominal). Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield were determined from the cell number at the respective observation times.

Significant inhibition of algal growth was observed at all tested concentrations for the endpoints growth rate and yield.

 

At the beginning and at the end of the test, the content of Manganese (Mn) as component of the test item in the test solutions was determined using ICP-OES-determination. Due the low content of Mn in the test item (only 3.411 % HMNO₄ in the whole test item), a good correlation between the HMnO₄ and the measured concentration was observed only at the start of the test at the highest tested concentration 100 mg/L (nominal). Through the test, the test item precipitated and was present in the test system but not quantifiable with the measurement system. Only in the two highest test concentrations could be Mn detected at the end of the test. Therefore, the determination of the biological results was based on the calculated concentrations (using dilution factor) from the measured value of the highest concentration at the start of the test.

 

The 72h-EC₅₀ values of potassium dichromate (K₂Cr₂O₇, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.65 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results for the test item Permanganic acid (3-5% in water) were determined:

Results of the test item

Endpoint	NOEC	LOEC	EC10	EC50
Growth Rate	< 0.03 mg/L	≤ 0.03 mg/L	0.07 mg/L	0.35 mg/L
Yield	< 0.03 mg/L	≤ 0.03 mg/L	0.02 mg/L *	0.09 mg/L

* Value was extrapolated by the program.

Note: According to the guideline, NOEC is determined by comparing of the respective treatment with the blank control using a hyphothesis test. Statistically insignificant variation is considered as “no observed effect”, although the EC₁₀ which is read from the graph toxicity vs. concentration may lie lower.

 

 

Key value for chemical safety assessment

EC50 for freshwater algae:

0.35 mg/L

EC10 or NOEC for freshwater algae:

0.07 mg/L