Reaction products of sodium glucoheptonate with manganese sulfate and sodium hydroxide

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: complete raw data not given. However, the available data indicates that the test was well performed similar to OECD Guideline 221 with minor deviations and meets general scientific requirements.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Reference

There is no data available for the target substance manganese glucoheptonate on acute toxicity towards aquatic algae. However, there is data available for the source substances sodium gluconate, gluconic acid and manganese chloride. This data is used within a frame of a weight-of-evidence approach to assess the toxicity of manganese glucoheptonate (MnGHA).

The MnGHA EC50s range from 24.11 to 2222.18 mg/L for various different freshwater species and the 10d EC10s range from 12.82 to 598.28 mg/L. The key value for chemical safety assessment for freshwater algae is set to the lowest reported EC50 value of 24.11 mg/L which was obtained forSelenastrum capricornutum (Pseudokirchneriella subcapitata)within a 14 d study by Christensen et al (1979).

EC50(14d): 24.11 mg/L for Selenastrum capricornutum (Christensen et al, 1979).

EC50 for freshwater algae:

24.11 mg/L

gluconic acid and sodium gluconate

The toxicity of Sodium gluconate (CAS 527-07-1) towards algae has been determined according to OECD Guideline 201 in compliance with GLP (OECD SIDS, 2004). Two tests have been performed. In the first test, 1000 mg/L of the test item have been tested. However, a decrease of the test item concentration was observed and therefore the test could not meet the stability requirements. Conclusively, a second test with 100 and 1000 mg/L test concentration was performed. Desmodesmus subspicatus CHODAT (strain No 86.81 SAG) was used as test organism. An initial cell density of 10 x 10E4 algae/mL was applied. For the second test 3 flasks with 100 mg/L, 3 flasks with 1000 mg/L and 6 flasks without test item were used. The common OECD procedure has been modified by covering the test vessels with glass petri dishes to prevent contamination by micro-organisms. After 24, 48 and 72 hours, cell concentration was determined using a microscope with a counter chamber (8 fields counted). No cell growth inhibition at 100 mg/L was determined. At 1000 mg/L, 70% cell growth inhibition was observed. For the average specific growth rate, no inhibition at 100 mg/L but 42% inhibition at 1000 mg/L was determined. The cell concentrations in controls increased by a factor of 65.9 after 72h. As final results and based on growth rate, an EC50 (7h) of > 100 mg/L and a NOEC (72h) of 100 mg/L were derived.

 

There was an additional acute toxicity study of Sodium gluconate (CAS 527-07-1) according to OECD Guideline 201 in compliance with GLP (OECD SIDS, 2004). A range-finding test was conducted prior to the definitive test to enable the following concentrations in the definitive test: 0 (control), 100, 180, 320, 560, 1000 mg/L (nominal concentrations). Measured concentrations of the test substance in the test solutions at the beginning of exposure were +/-20 % of the nominal concentrations. As test organism, Pseudokirchneriella subcapitata has been used (Biomass loading: 1 x 10 E04 cells/mL). As final results, the EC50 (72h) was determined to be >1000 mg/L while the NOEC (72h) was set to 560 mg/L based on the growth rate (nominal concentration).

 

Acute toxicity of four relatively new chelating agents and their equimolar manganese and cadmium complexes was studied (Silanpää et al., 2003). The chelating agents studied were gluconic acid (GA),β-alaninediacetic acid (ADA), diethylenetriaminepentakismethylenephosphonic acid (DTPMP), and nitrilotriacetic acid (NTA).The bioassay with R. subcapitata using gluconic acid was performed according to a Finnish standard SFS 5072 (1986, Toxicity test with pure culture of algae). At the time of an inoculation, the alga was in its exponential growth phase. During the test, the flasks were shaken in every 24h. The volume in all tests was 10 mL and illumination intensity was set to 5000 lx. Temperature was maintained at 22 ± 1°C throughout the 72h test. Two simultaneous experiments were performed for each test concentration and the highest concentration of chelating agents was 1000 mg/L. The growth was estimated with in vivo fluorescence of chlorophyll (Labsystems, Fluoroskan Ascent) and the results obtained from the bioassay are expressed as 72h EC50 values with 95% confidence interval. The EC50 (72h) value for gluconic acid is reported as 76 mg/L.R. subcapitata proved the most sensitive to these compounds compared to Daphnia magna and Photobacterium phosphoreum.

manganese chloride

Data on the toxicity of manganese to algae and aquatic plants was reviewed. In the reviewed studies three different freshwater algae (Selenastrum capricornutum, Chroococcus limneticus and Plectonema boryanum), as well as the floating aquatic vascular plants Lemna minor (Duckweed) and one marine algae were used as test organisms. The reported effect concentrations (EC10 and EC50) for the test substances were stated as mg Mn/L.

The data on manganese compounds allows estimating a corresponding EC for manganese glucoheptonate providing that no toxicity is attributed to the glucoheptonate ion, that the absorption of manganese from this manganese compounds is 100 % and all manganese became systemically available. 

 

Algal assays were conducted by Christensen et al (1979) to observe the response of the freshwater alga Selenastrum capricornutum and the marine algae Chlorella stigmatophora to the metals manganese, copper and lead added singly or in combination to both artificial media and natural waters. Thereby, only the effects induced by manganese in artificial waters are of importance for this read-across purpose.

Growth rates and average cell volumes were assessed by the authors. While the growth rate, based on cell volume, in all cases decreased with increasing metal concentration, the average cell volume does not follow a similarly, consistent pattern. Manganese has only a slight effect on the average cell volume. It is concluded that main effects and interactions occur rather regarding to the total cell number than concerning the total cell volume. This means that the cell volume as a measure of the total biomass is less affected by manganese than the total cell number.

The marine water algae Chlorella stigmatophora showed a 50 % reduction in the total algal cell volume in 28 ppt ASW plus full SAAM (standard algal assay medium) nutrients in the presence of 50 mg manganese per liter added singly. The study was conducted for approximately 21 days, so the reported concentration of 50 mg/L is regarded as the 21d EC50. The corresponding 21d EC50 for manganese glucoheptonate is calculated to be 388.92 mg/L for Chlorella stigmatophora.

Christensen et al (1979) also assay the freshwater algae Selenastrum capricornutum in SAAM. A 50 % reduction in the total algal cell volume occurs in the presence of 3.1 mg manganese per liter added singly. The study was conducted for approximately 14 days, so the reported concentration of 3.1 mg/L is regarded as the 14d EC50. This value corresponds to a 14d EC50 of 24.11 mg/L for manganese glucoheptonate for Selenastrum capricornutum.

 

The effect of manganese chloride on Chroococcus limneticus and two mutants of Plectonema boryanum was investigated by Singh and Kashyap (1978). In a 10 d toxicity study, cultures of Chroococcus limneticus and Plectonema boryanum were placed on nutrient agar plates with various concentrations of MnCl2 incorporated (1 -10 mM), i.e. under static conditions. The EC50 and the EC10 values based on the count of surviving colonies were 5.2 mmol/L and 1.4 mmol/L for C. limneticus and 0.2 mmol/L and 0.03 mmol/L for P. boryanum, respectively. The following abnormalities were noted: asymmetry in cell division, abnormal cell enlargement. This toxicity study was classified as acceptable and reliable with restrictions and satisfies general scientific requirement for a 10 d toxicity study in algae. Although no standard guideline was followed, two different strains of algae tested and the documentation and given results indicate that the study was well-performed and satisfies general scientific requirements. So the study is classified as reliable with restrictions. The corresponding 10d EC50 for manganese glucoheptonate is 85.47 mg/L for Plectonema boryanum and 2222.18 mg/L for Chroococcus limneticus. The 10d EC10 for manganese glucoheptonate are 598.28 and 12.82 mg/L for Plectonema boryanum and Chroococcus limneticus, respectively.

 

In a 4 d acute toxicity study, the freshwater floating aquatic vascular plant Lemna minor were exposed to Manganese at 6 different concentrations under static conditions similar to OECD Guideline 221. The EC50 values based on growth rate determined by front number compared to control was 31 mg/L Manganese. This toxicity study was classified as acceptable and satisfies the guideline requirement for a Lemna Growth inhibition test with minor restrictions.

The study is classified as reliable with restrictions because of the testing similar to OECD Guideline 221 and the results indicate, that the study was well-performed and satifies general scientific requirements. Consequently, the results can be considered to be reliable. Additionally, the test organism Lemna minor broadens the spectrum of aquatic organisms and, as an additional model, allows a deeper insight in the expectable effects of the test substance on the aquatic environment. Therefore, these results should be also taken into account when assessing the need for classification. A 4d EC50 value of 31 mg/L Mn2+ was obtained. The 4d EC50 for manganese glucoheptonate is 241.13 mg/L for Lemna minor.

 

Conclusion

The MnGHA EC50s range from 24.11 to 2222.18 mg/L for various different freshwater species and the 10d EC10s range from 12.82 to 598.28 mg/L. The key value for chemical safety assessment for freshwater algae is set to the lowest reported EC50 value of 24.11 mg/L which was obtained for Selenastrum capricornutum (Pseudokirchneriella subcapitata) within a 14 d study by Christensen et al (1979).

 

Only one EC50 was obtained for marine water algae. This value is not used as key value for chemical safety assessment for marine water algae because it can not be validated in comparison with further EC values of marine water species to assess the reliability.

Table 1: Effect concentrations (EC) derived from studies performed with various manganese compounds and converted to manganese glucoheptonate (MnGHA).

Species	Duration of exposure	Dose descriptor	Mn GHA (70%) mg/L	Impact	Reference
Chlorella stigmatophora	21d	EC50	388.92	salt water	Christensen et al, 1979
Selenastrum capricornutum	14d	EC50	24.11	freshwater	Christensen et al, 1979
Chroococcus limneticus	10d	EC50	2222.18	freshwater	Singh and Kashyap, 1975
Plectonema boryanum	10d	EC50	85.47	freshwater	Singh and Kashyap, 1975
Chroococcus limneticus	10d	EC10	598.28	freshwater	Singh and Kashyap, 1975
Plectonema boryanum	10d	EC10	12.82	freshwater	Singh and Kashyap, 1975
Lemna minor	4d	EC50	241.13	freshwater	Wang, 1986

Data source

Reference

Reference Type:

publication

Title:

Toxicity Tests of Aquatic Pollutants by Using Common Duckweed

Author:

Wang W

Year:

1986

Bibliographic source:

Environmental Pollution (Series B) 11 (1986) 1-14

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

Deviations:

yes

Remarks:

Test substance incubation only 4 d

Principles of method if other than guideline:

Duckweed colonies were exposed to several concentrations of the test item. After 4 days, the number of fronds was counted

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Mn(II)

IUPAC Name:

Mn(II)

Test material form:

not specified

Details on test material:

- Name of test material (as cited in study report): Mn(II)
- Molecular formula (if other than submission substance): Mn
- Substance type: inorganic cation
- Analytical purity: Reagent grade

Sampling and analysis

Analytical monitoring:

not specified

Test organisms

Test organisms (species):

Lemna minor

Details on test organisms:

TEST ORGANISM
- Common name: Duckweed
- Strain: Lemna minor
- Source (laboratory, culture collection): Duckweed stock was collected from a pond located inside the Illinois State Water Survey property during the spring of 1982. The stock was maintained in the laboratory in a polypropylene tray with 20 litre capacity. To the tray was added a small amount of sediment, collected from the same pond, 10 litres of pond water and 5 litres of cold tap water. The plants were illuminated with cool-white fluorescent lights. Every 3-4 days cold tap water was added to maintain the water level.
Twenty-four hours before the toxicity experiment was initiated, duckweed samples were selected for tests. A scoopful of duckweed from the stock was placed in a small tray containing cold tap water. The test specimens were selected from this tray and transferred to a second tray containing only deionized water. The test specimens must appear healthy, with two fronds of approximately equal size per colony. Care was exercised so as not to injure the plant. The selected duckweed colonies were sealed from light and were ready for experiment. The purpose of the light exclusion was to prevent growth during the holding period. The colony was discarded if it grew, or if it appeared unhealthy.
Approximately twice a year, the stock was discarded and restocked with fresh duckweed.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

4 d

Test conditions

pH:

7.5

Nominal and measured concentrations:

6 different concentrations

Details on test conditions:

TEST SYSTEM
- Incubation chamber used: no data; Temperature was maintained at 27 ° ± 2 °C
- Test vessel: fruit jar
- Material, size, headspace, fill volume: 200 ml test solution
- Type of cover: watch glas
- No. of colonies per vessel: 20
- No. of fronds per colony: 2
- No. of vessels per concentration (replicates): 3-6

GROWTH MEDIUM
- Standard medium used: yes, algal nutrient solution suggested in Standard Methods (1980)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water

OTHER TEST CONDITIONS
- Sterile test conditions: no data
- Adjustment of pH: yes, pH 7.5
- Photoperiod: constant illumination during tests
- Light intensity and quality: illumination was provided by cool-white fluorescent light with an intensity of 6456 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of frond number: manual counting

Reference substance (positive control):

not specified

Results and discussion

Effect concentrations

Duration:

4 d

Dose descriptor:

EC50

Effect conc.:

31 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Mn(II)

Basis for effect:

growth rate

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

The testing was performed similar to OECD guideline 221, the documentation and given results indicate that the study was well-performed and satisfies general scientific requirements. So the study is classified as reliable with restrictions and consequently, the results can be considered to be reliable. Additionally, the test organism Lemna minor broadens the spectrum of aquatic organisms and, as an additional model, allows a deeper insight in the expectable effects of the test substance on the aquatic environment. Therefore, these results should be also taken into account when assessing the need for classification.
A 4 d EC50 value of 31 mg/L Mn2+ was obtained.

Executive summary:

In a 4 d acute toxicity study, the freshwater floating aquatic vascular plants Lemna minor were exposed to Manganese at 6 different concentrations under static conditions similar to OECD Guideline 221. The EC50 values based on growth rate determined by front number compared to control was 31 mg/L Manganese.

This toxicity study was classified as acceptable and satisfies the guideline requirement for a Lemna Growth inhibition test with minor restrictions.