Barium tartrate

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:

4 - 29 May 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to the OECD 201 Guideline and complied with the principles of GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

(2006, Annex 5 corrected 28 July 2011)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Barium tartrate

EC Number:

227-615-9

EC Name:

Barium tartrate

Cas Number:

5908-81-6

Molecular formula:

C4H4O6Ba

IUPAC Name:

Barium L(+)-(2R,3R)-tartrate

Test material form:

solid: particulate/powder

Remarks:

migrated information: powder

Details on test material:

- Name of test material (as cited in study report): Barium tartrate
- Appearance: White powder

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Samples of 4.8 mL for possible analysis were taken from all test concentrations and the control at t=0 h and t=72 h and stored in a freezer until analysis. In addition, the filter containing undissolved residue was retained for possible analysis.
At the end of the exposure period, the replicates with algae were pooled at each concentration before sampling.
On the day of analysis, the test samples were defrosted at room temperature. The samples were diluted in a 25:1 (v:v) ratio with HNO3 and analysed. If necessary, the samples were further diluted with 4% HNO3 in M2-medium to obtain concentrations within the calibration range.

Test solutions

Vehicle:

no

Details on test solutions:

Preparation of test solutions started with a loading rate of 100 mg/L applying a 2-day period of magnetic stirring followed by a filtration through a 0.45 µm membrane filter (RC55, Whatman). The obtained Water Soluble Fraction (WSF) was used as the highest concentration. The lower test concentrations were prepared by subsequent dilutions of the highest concentration in test medium. The final test solutions were all clear and colourless.
After preparation, volumes of 50 mL were added to each replicate of the respective test concentration. Subsequently, 1 mL of an algal suspension was added to each replicate providing a cell density of 10^4 cells/mL.

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture.
- Age of inoculum (at test initiation):
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24°C. 3 days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 1 x 10^4 cells/mL. The pre-culture was maintained under the same conditions as used in the test. The cell density was measured immediately before use.

ACCLIMATION
- Culturing media and conditions (same as test or not): Pre-culture medium is same as test (M2)

Study design

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Post exposure observation period:

None

Test conditions

Hardness:

24 mg CaCO3/L

Test temperature:

21.9 -23.0 ºC

pH:

7.9-8.4

Dissolved oxygen:

Not measured

Salinity:

Not applicable

Nominal and measured concentrations:

Test groups represented 1.0, 3.2, 10, 32 and 100% of the WSF prepared at a loading rate of 100 mg/L, respectively.
At the start of the test, the actual test concentrations were between 80 and 87% relative to the expected loading rates. The concentrations remained stable at 97 to 101% of initial during the 72-hour test period. The range tested based on actual exposure concentrations corresponded therefore with 1.0, 3.2, 10, 32 and 100 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL, all-glass, containing 50 mL of test solution
- Aeration: no
- Initial cells density: 1x 10^4 cells/mL
- Control end cells density: 125 x 10^4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (M2)

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuously
- Light intensity and quality: TLD-lamps with a light intensity within the range of 78 to 83 µE.m-2.s-1.

EFFECT PARAMETERS MEASURED :
- Algal density at t = 0 , 24, 48 and 72h. The test solutions at 100% WSF after 72 hours in the combined range-finding/limit test contained particles. It was consequently decided that spectrophotometric measurement could be disturbed in the final test. Therefore algal density was determined by use of a microscope and a counting chamber throughout the final tests.

TEST CONCENTRATIONS
- combined limit/range-finding test with solutions containing 0.1, 1.0, 10 and 100% of a WSF prepared at a loading rate of 100 mg/L.
- definitive test with solutions containing 1.0, 3.2, 10, 32 and 100% of the WSF prepared at a loading rate of 100 mg/L

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

11 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 7.7 - 15 mg/L / The nominal concentrations were analytically confirmed (recovery > 80%)

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI 0.86 - 3.7 mg/L / The nominal concentrations were analytically confirmed (recovery > 80%)

Details on results:

Growth rates were in the range of the controls at the concentrations 1.0 and 3.2 mg/l during the 72-hour test period, whereas the growth rate of algae exposed to 10 mg/l and higher were increasingly reduced.
Statistically significant inhibition of growth rate was found at the lowest test concentration of 1.0 mg/l and at concentrations of 10 mg/l and higher. The NOEC was set at the in-between concentration of 3.2 mg/l despite the statistical significant reduction at the lower test group of 1.0 mg/l. Note further that the reduction in both groups was far below the biological relevant 10% level

Microscopic observations at the end of the test revealed a normal and healthy appearance of the exposed cells when compared to the control.

Acceptability of the test:
- In the controls, cell density increased by an average factor of >16 within 2 days (i.e. 69).
- The mean coefficient of variation for section-by-section specific growth rates in the control cultures did not exceed 35% (i.e. 35%).
- The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures did not exceed 7% (i.e. 2.6%).

Results with reference substance (positive control):

The EC50 for growth rate inhibition (72h-ERC50) was 1.3 mg/L with a 95% confidence interval ranging from 1.1 to 1.5 mg/L. The historical ranges for growth rate inhibition lie between 0.82 and 2.3 mg/L. Hence, the 72h-ERC50 for the algal culture tested corresponds with this range.

Any other information on results incl. tables

Table 1            Percentage inhibition of growth rate (total test period) during the final test

Barium tartrate Concentration (mg/l)	Mean	Std. Dev.	n	%Inhibition
Control	1.411	0.0361	6	0.0
1.0	1.370	0.0111	3	2.9*
3.2	1.362	0.0371	3	3.5^#
10	0.531	0.0099	3	62.4*
32	0.427	0.0786	3	69.7*
100	0.025	0.0429	3	98.2*

* - effect was statistically significant

^#- effect biologically insignificant (<10%)

 

Table 2            Percentage inhibition of growth rate at different time intervals during the final test

Barium tartrate Concentration (mg/l)	n	0 – 24 h		24 – 48 h		48 – 72h
		Mean	%Inhibition	Mean	%Inhibition	Mean	%Inhibition
Control	6	0.859	0.0	1.685	0.0	1.689	0.0
1.0	3	0.986	-14.8	1.397	17.1	1.728	-2.3
3.2	3	0.842	1.9	1.355	19.6	1.888	-11.8
10	3	0.833	2.9	0.254	84.9	0.505	70.1
32	3	0.846	1.5	-0.158	109.4	0.594	64.9
100	3	0.345	59.9	0.112	93.3	-0.382	122.6

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study with Pseudokirchneriella subcapitata, 72h-ErC50 was 11 mg/L and the 72h-ErC10 was 2.3 mg/L.

Executive summary:

A 72-h algae growth inhibition test was performed with the substance according to OECD 201 and in compliance with GLP principles. Test groups represented 1.0, 3.2, 10, 32 and 100% of the WSF prepared at a loading rate of 100 mg/L, respectively. At the start of the test, the actual test concentrations were between 80 and 87% relative to the expected loading rates. The concentrations remained stable at 97 to 101% of initial during the 72-hour test period. The range tested based on actual exposure concentrations corresponded therefore with 1.0, 3.2, 10, 32 and 100 mg/L.

Under the conditions of the present study with Pseudokirchneriella subcapitata, 72h-ErC50 was 11 mg/L and the 72h-ErC10 was 2.3 mg/L