Barium peroxide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

25.01.2010 - 28.01.2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Further information in a detailed justification report is included as attachment to the same iuclid record point.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
For the determination of analogue in this read-across approach, the following points have been considered:
- Chemical speciation and valency (common barium cation: Ba2+).
- The water solubility, as it provides a first indication of the availability of the metal ion in the different compartments of interest. The most simplistic approach to hazard evaluation is to assume that the specific metal-containing compound to be evaluated shows the same hazards as the most water-soluble compounds.
- In fluids of organisms and in in aqueous media, dissociation of barium peroxide takes place immediately, resulting in formation of barium cations (Ba2+) and oxygen. Thus, any ingestion or absorption of barium peroxide by living organisms, in case of systemic consideration, will inevitably result of exposure to the dissociation products.
- Oxygen (formed during the dissociation of barium peroxide) is of low (eco)toxicological relevance when ingested and taken up systemically. Thus, any possible toxicological or ecotoxicological effect triggered by barium peroxide exposure can be attributed to barium.
- Counter ions: the assumption that the metal ion is responsible for the common property or effect implies that the toxicity or ecotoxicity of the counter ion present in the compound will be largely irrelevant in producing the effects to be assessed.
- Likely common breakdown products via physical and/or biological processes for the targeted substance (barium peroxide) and the analogues identified cannot present strong differences since the structures are very simple and very similar (formation of Ba2+ ion).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Source chemical information is provided in the “source” endpoint. No impurity affecting the classification is reported for the source chemical.
Information on the impurities of the target chemical are detailed in the attached report.

3. ANALOGUE APPROACH JUSTIFICATION
The main hypothesis are presented in the detailed report attached. The experimental data performed on the substance (tests performed in this REACH registration dossier on strontium peroxide) consolidates the approach performed.

4. DATA MATRIX
A data matrix is presented in the detailed report attached.

Reason / purpose for cross-reference:

read-across source

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

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

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 30.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

total Ba

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 30.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element

Remarks:

total Ba

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

barium dichloride dihydrate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

barium dichloride dihydrate

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 85.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: barium dichloride

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 85.3 mg/L

Nominal / measured:

nominal

Conc. based on:

other: barium dichloride

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.

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.

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 (72 h)	Significant difference to control (p≤0.05)	%Inhibition of Growth Rate (72 h)	Significant difference to control (p≤0.05)
Control	0.0	No	0.0	No
1.0	0.6	No	0.1	No
3.2	6.9	No	1.3	No
10.0	17.3	No	4.6	No
31.6	4.6	No	0.9	No
100	5.9	No	1.1	No
EC50	> 100.0 > 100.0		>100.0
NOEC	>= 100.0		>= 100.0
LOEC	> 100.0		> 100.0

Validiy 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%)

Validity criteria fulfilled:

yes

Conclusions:

No statistically significant differences were found between the control and any test item concentration up to and including 100 mg barium dichloride dihydrate/L.

Hence the recovery rates (RR) are < 80% the results are given as actual (geometric mean measured) concentrations.

The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >1.74 mg BaCl2 (1.15 mg Ba/L). The no-observed effect concentration (NOEC) is ≥ 1.74 mg BaCl2/L (1.15 mg Ba/L) based on dissolved barium concentrations.

However, based on total barium concentrations the results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is > 45.6 mg BaCl2/L (30.1 mg Ba/L). The no-observed effect concentration (NOEC) is ≥ 45.6 mg BaCl2/L (30.1 mg Ba/L).

These data are considered relevant in a read across approach for Barium peroxide since they are based on dissolved barium concentration and they can be used for hazard and risk assessment purposes (classification; PNEC-derivation).

Description of key information

A test was performed on barium dichloride. No statistically significant differences were found between the control and any test item concentration up to and including 100 mg barium dichloride dihydrate/L. Hence the recovery rates (RR) are < 80% the results are given as actual (geometric mean measured) concentrations.

The results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is >1.74 mg BaCl2 (1.15 mg Ba/L). The no-observed effect concentration (NOEC) is ≥ 1.74 mg BaCl2/L (1.15 mg Ba/L) based on dissolved barium concentrations.

However, based on total barium concentrations the results of the study demonstrate that the EC50 for Pseudokirchneriella subcapitata is > 45.6 mg BaCl2/L (30.1 mg Ba/L). The no-observed effect concentration (NOEC) is ≥ 45.6 mg BaCl2/L (30.1 mg Ba/L).

These data are considered relevant in a read across approach for Barium peroxide since they are based on dissolved barium concentration and they can be used for hazard and risk assessment purposes (classification; PNEC-derivation).

Key value for chemical safety assessment

EC50 for freshwater algae:

1.74 mg/L

EC10 or NOEC for freshwater algae:

45.6 mg/L

Additional information

The value is greatly above the cut off value of 1mg/L, consequently it does not need to be classified as acute toxicity for the environment.