Barium carbonate

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP study according to International guidelines. Total and dissolved Ba-levels were reported

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Chemical analysis of test concentrations at start and end of exposure
- at the beginning of the test, duplicate samples of each of the test solutions and the control were taken.
- at the end of the test, immediately after determination of the biological and physico-chemical parameters, the test solutions of the replicates of each treatment were mixed. Duplicate samples were taken from the control, each of the test solutions and from the test vessels without algae with the highest test item concentration.

Vehicle:

no

Details on test solutions:

The algal medium (Kuhl and Lorenzen, 1964) consists of trace elements and macronutrients in the following final concentrations:
KNO3: 1011.1 mg/L
NaH2PO4 * 1 H2O: 621.0 mg/L
Na2HPO4 * 2 H2O: 89.0 mg/L
MgSO4 * 7 H2O: 246.5 mg/L
CaCl2 * 2 H2O: 14.7 mg/L
FeSO4 * 7 H2O: 6.9 mg/L
Titriercomplex III: 9.3 mg/L
H3BO3: 0.061 mg/L
MnSO4 * 1 H2O: 0.169 mg/L
ZnSO4 * 7 H2O: 0.287 mg/L
CuSO4 * 5 H2O: 0.00249 mg/L
(NH4)6Mo7O24 * 4 H2O: 0.01235 mg/L
100 mg of the test item was mixed into 1,000 mL algal medium in a 1,000 mL measuring flask, resulting in a nominal concentration of 100 mg test item/L. The solution was shaken for 3 minutes at room temperature.

Test organisms (species):

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

Details on test organisms:

Pseudokirchneriella subcapitata (SAG 61.81) was supplied by Georg-August-Universität Göttingen, D-37073 Göttingen, Germany (Date of receipt: December 18, 2009)
Amount of liquid stock culture per pre-culture vessel: 100 mL
Pre-culture vessels: 300 mL Erlenmeyer flasks
Number of cells per mL in the pre-culture before inoculating the test solution: 88.5E4
Number of replicates: 2
Light: light/dark (24/0 h); fluorescent tubes of universal white type
Light intensity: 60 – 120 µE/m2 * s
Shaker: 100 ± 5 oscillations/min
Temperature in the test room: 21 - 24°C, controlled at ± 2°C

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.9 +/- 0.6 degrees Celcius (mean +/- SD)

pH:

start of test: 5.8-5.9 (all test concentrations)
end of test: 6.0-6.1 (all test concentrations)

Dissolved oxygen:

not relevant for algal testing

Nominal and measured concentrations:

Nominal: 0, 1.0, 2.2, 10, 31.6 and 100 mg test item/L
Measured concentrations: Measured concentrations of dissolved test item in 0.45 μm-filtered test solutions were between 2 and 25% of the nominal concentrations. Analysis of total Barium in non-filtered, acidified test solutions resulted in recoveries of 12 and 61% of the nominal concentrations.
(For details see Table 2 and 3 in 'Any other information on results incl. tables').

Details on test conditions:

Test units: 300 mL Erlenmeyer flasks
Volume of test solution per test vessel: 100 ml
No. of test concentrations (incl. control): 6
No. of replicates in the control: 6
No. of replicats per test concentration: 3
Test medium: Algal medium (Kuhl & Lorenzen, 1964)
The concentration of the algal cells in the test solutions at the beginning of exposure was approximately 0.5 * 1E4 cells per mL.
Endpoints: EC50, NOEC, LOEC
Biological parameters: Inhibition of growth in relation to control (growth rate & yield)
Light regime: permanent at 93.6 µE/m2 * s (mean; required is 60-120 µE/m2 * s).
Types of light: fluorescent tubes of universal white type (Osram Lumilux 58W/865)
For chemical analysis at the end of the test, two additional test vessels without algae were prepared at the highest test item concentration in order to assess test item stability during exposure without the presence of algae (stability samples).
Determination of cell number: THOMA Counting Chamber with Microscope Ortholux II, Ernst Leitz KG, Wetzlar, Germany; Multiple Reader Tecan ULTRA, Tecan Deutschland GmbH, Crailsheim, Germany

After 24, 48 and 72 hours, the cell numbers were determined by measuring the fluorescence intensity in 4 samples of 200 µL of test solution per replicate using a fluorometer (Multiple Reader Tecan ULTRA). The results [RFU, relative fluorescence units] were converted into biomass concentration [cells/mL] using a calibration line. A dilution series of the pre-culture was used to determine the calibration line by comparison of cell numbers (counted using a microscope) and fluorescence intensity (measured using a fluorometer) in consideration of background fluorescence of the blank algal medium.

Reference substance (positive control):

yes

Remarks:

K2Cr2O7 (potassium dichromate)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1.15 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

Ba

Basis for effect:

growth rate

Remarks on result:

other: highest measured level

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 1.15 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

Ba

Basis for effect:

growth rate

Remarks on result:

other: highest measured level

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 30.07 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

total Ba

Basis for effect:

growth rate

Remarks on result:

other: highest measured level

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 30.07 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

total Ba

Basis for effect:

growth rate

Remarks on result:

other: highest measured level

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

No statistically significant differences (Table 1) were found between the control and the test item concentrations up to 100 mg test item/L. The EC50 (72 h) based on nominal concentrations was therefore determined to be higher than the highest concentration of 100 mg test item/L. The results of the study demonstrate that the no-observed effect concentration for Pseudokirchneriella subcapitata for the parameters yield and growth rate is ≥ 100 mg test item/L (nominal concentration).

Samples from the test solutions were analysed to determine the actual test item concentration in comparison to the nominally applied concentration. Measured concentrations of dissolved test item in 0.45 µm-filtered test solutions were between 2 and 25% of the nominal concentrations. Analysis of total Barium in non-filtered, acidified test solutions resulted in recoveries of 12 and 61% of the nominal concentrations.
Considering the measured concentrations as based on total measured Barium content, the EC50 for Pseudokirchneriella subcapitata is > 61.1 mg test item/L (measured in the highest concentration at test end). The no-observed effect concentration (NOEC) is ≥ 61.1 mg/L Barium Chloride Dihydrated

Results with reference substance (positive control):

The reference item potassium dichromate (K2Cr2O7) is tested at least twice a year in order to determine the sensitivity of the organisms from the culture, and to demonstrate that the test conditions are appropriate. Results of the reference test performed in January 2010:
- EbC50: 0.23 mg/L
- ErC50: 0.85 mg/L
Based on an international ring test (ISO 2004) mentioned in OECD guideline 201, the ErC50 (72h)-values for potassium dichromate obtained from different laboratories should be 1.19 mg/L with a standard deviation of 0.27 mg/L.
The EC50 value for the toxic reference item, potassium dichromate, was determined as 0.85 mg/L. This value is within the historical range of the results of our laboratory (mean EC50 value = 1.15 ± 0.42 mg/L) and within the upper (2.54 mg/L) and lower (0.44 mg/L) warning limit. The warning limits were calculated as two standard deviations from the historical mean of the EC50 (all calculated using the log concentration; according to Environment Canada 2005). Furthermore, the EC50 value is within the refined range of 1.10 ± 0.48 mg/L, recommended based on an international ring test (Pattard et al. 2009). Therefore, the results of this reference test are acceptable and the test conditions are reliable.

Reported statistics and error estimates:

Range-to-standard-deviation-ratio Test on Normal Distribution; Cochran´s Test on Variance Homogeneity; One-way Analysis of Variance (ANOVA)
The statistical software package ToxRat 2.10 Professional (ToxRat Solutions GmbH, Naheweg 15, D-52477 Alsdorf) was used for these calculations.

Table 1: Summary of tests results based on statistical evaluation of biological results and nominal concentrations of the test item  

Treatment (mg test item/L)	% Inhibition of Yield (72h)	Significant difference to control (p≤0.05)	% Inhibition of Growth (72h)	Significant difference to control (p≤0.05)
Control	0.00	No	0.00	No
1.0	0.55	No	0.06	No
3.2	6.93	No	1.29	No
10.0	17.30	No	3.43	No
31.6	4.62	No	0.89	No
100	5.87	No	1.08	No
EC50	>100.0		>100.0
NOEC	≥100.0		≥100.0
LOEC	>100.0		>100.0

Validity of test:

- Mean biomass increase in the control cultures: 252.0 (required: factor of at least 16 within the 72h test period

- Mean coefficient of variation for section-by-section specific growth rates in the control cultures: 22.8% (required: up to 35%)

- Coefficient of variation of average specific growth rates during test period in replicate control cultures: 1.4% (required: up to 7%)

Table 2: Results of barium determination in filtered samples (dissolved barium)

Test period (h)	Concentration BaCl2·2H2O (mg/L)	Barium Analyzed (mg/L)	Test Item (BaCl2·2H2O) in sample (mg/L)	% of Nominal
0	0	<LOD	<LOD	-
0	1.0	0.139	0.247	25
0	3.2	0.213	0.379	12
0	10.0	0.646	1.15	11
0	31.6	1.923	3.42	11
0	100.0	1.332	2.37	2
72	0	<LOD	<LOD	-
72	1.0	0.054	0.096	10
72	3.2	0.111	0.198	6
72	10.0	0.359	0.639	6
72	31.6	0.839	1.49	5
72	100.0	0.999	1.78	2
72	100.0	1.117	1.99	2

 

Table 3: Results of barium determination in extracted samples (total barium)

Test period (h)	Concentration BaCl2·2H2O (mg/L)	Barium Analyzed (mg/L)	Test Item (BaCl2·2H2O) in sample (mg/L)	% of Nominal
0	0	<LOD	<LOD	-
0	1.0	0.312	0.555	56
0	3.2	0.211	0.376	12
0	10.0	3.649	6.49	65
0	31.6	2.179	3.88	12
0	100.0	26.32	46.8	47
72	0	<LOD	<LOD	-
72	1.0	0.196	0.348	35
72	3.2	0.271	0.481	16
72	10.0	3.205	5.704	58
72	31.6	8.673	15.43	49
72	100.0	34.31	61.05	61
72	100.0	30.10	53.56	54

 

Validity criteria fulfilled:

yes

Conclusions:

The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >100 mg test item/L. The no-observed effect concentration (NOEC) is ≥100 mg/L Barium Chloride Dihydrate based on nominal concentrations.

Executive summary:

A GLP-compliant OECD 201 guideline study with alga (Pseudokirchneriella subcapitata) is available for barium chloride dihydrate. Algae were exposed to nominal concentrations of 1.0, 3.2, 10.0, 31.6 and 100.0 mg/L and a control under static conditions for 72 hours. To study exposure to the test substance, samples of the test solution were taken and analysed with ICP-OES at the beginning and at the end of the test. Samples of the test solutions were either filtered (0.45 µm) or extracted to determined the concentration of dissolved and total barium, respectively. Measured concentrations of dissolved test item in 0.45 μm-filtered test solutions were between 2 and 25% of the nominal concentrations. Analysis of total Barium in non-filtered, acidified test solutions resulted in recoveries of 12 and 61% of the nominal concentrations.

No statistically significant differences were found between the control and any test item concentration up to and including 100 mg test item/L. The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >100 mg test item/L. The no-observed effect concentration (NOEC) is ≥100 mg/L Barium Chloride Dihydrate based on nominal concentrations. Considering the measured concentrations, the EC50 for Pseudokirchneriella subcapitata is > 61.1 mg test item/L (measured in the highest concentration at test end). The no-observed effect concentration (NOEC) is ≥ 61.1 mg/L Barium Chloride Dihydrated.

Description of key information

One reliable acute/chronic toxicity data point (Klimisch 1, GLP) for an algae species – the green alga Pseudokirchneriella subcapitata – has been identified. Based on measured dissolved barium concentrations in the water column, a 72h-ErC50 and 72h-NOEC of >1.15 and >=1.15 mg Ba/L, resp. is reported by Egeler and Kiefer (2010), using  BaCl2 dihydrated as test substance.

Additional information

One reliable acute and chronic toxicity data point (Klimisch 1, GLP) for an algal species - the freshwater green algaPseudokirchneriella subcapitata- has been identified. No effect (growth rate) was noted at the highest (nominal) test concentration of 100 mg barium dichloride dihydrate/L.

Both the dissolved and total fration was measured. Dissolved levels were well below the theoretical expected levels, and this most likely due to formation the poorly soluble barium sulfate. At the highest nominal concentration of 100 mg Ba/L, the dissolved and total Ba concentration were 1.15 and 30.1 mg/L, respectively (geometric mean measured concentration). Therefore, based on total Ba-levels in solution, the ErC50 and NOEC are >30.1 and >=30.1 mg Ba/L, respectively. However, based on dissolved barium concentrations in solution, the ErC50 and NOEC are >1.15 and >=1.15 mg Ba/L, respectively.