Barium bis(dihydrogenorthophosphate)

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:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: samples of all tested concentrations were taken at test start and test end. The samples were immediately stabilised by adding 0.2 mL conc. HNO3 to 20 mL test media

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution with the hightest nominal test substance concentration was prepared. The lower test substance concentrations were prepared separately by diluting the highest concentration.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: 61.81 SAG.
- Source (laboratory, culture collection): SAG, Culture Collection of Algae at Pflanzenphysiologisches Institut of the University at Göttingen, Germany
- Method of cultivation: stock cultures were maintained acc. to OECD guideline

ACCLIMATION
- Acclimation period: A pre-culture was reared (3 days prior to test start)
- Culturing media and conditions (same as test or not): OECD standard growth medium

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Nominal and measured concentrations:

Nominal test substance concentrations: 0, 0.625, 1.25, 2.50, 5.00 and 10.0 mg/L,
equivalent to 0.251, 0.501, 1.00, 2.01 and 4.01 mg Ba/L,
equivalent to 0.117, 0.233, 0.467, 0.934 and 1.87 mg P/L.

Analytically determined concentrations:
at test start: 0.238, 0.483, 0.972, 1.93 and 3.90 mg Ba/L (94.8 – 97.3% of nominal).
after 72 hours: 0.245, 0.480, 0.990, 2.00 and 4.05 mg Ba/L (95.6 – 100.8% of nominal; 99.3 – 103.6% of initial).

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks (250 ml nominal volume)
- Fill volume: 100 mL
- Initial cells density: 10 000 cells/mL
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 8

GROWTH MEDIUM
- Standard medium used: yes, sterilised synthetic growth medium acc. to OECD guideline 201

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH: no
- Photoperiod: contionous illumination
- Light intensity and quality: 60 - 120 µE m-2 s-1 (OSRAM Standard “cool white”)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter (CASY 1 Model TT, OMNI Life Science GmbH & Co. KG, Bremen, Germany). The cell concentrations were determined after 24, 48 and 72 hours

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 1.0, 10 and 100 mg test item/L
- Results used to determine the conditions for the definitive study: inhibition of grwoth rate at 10 mg/L: 80.6%

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

6.07 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.86 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

2.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

A background value of barium in the control of 0.0001 mg Ba/L at test start was measured. The background concentration of barium at test end was below the LOD.
Since the test item concentrations were between 80 and 120% of nominal at test start and test end, the test evaluation was based on the nominal test item concentration.
Based on the Ba concentration the EC10(72 h) was > 1 mg Ba/L.

Results with reference substance (positive control):

Nominal ErC50 (obtained in August 2015): 2.62 mg/L (2.52 - 2.72 mg/L, 95 % confidence limits).

Validity criteria fulfilled:

yes

Additional information

The acute toxicity of barium bis(dihydrogen orthophosphate) to aquatic algae was investigated in a study following OECD guideline 201 (Fraunhofer, 2017). Raphidocelis subcapitata was exposed to nominal test substance concentrations of 0.625, 1.25, 2.50, 5.00 and 10 mg/L (equivalent to 0.251, 0.501, 1.00, 2.01 and 4.01 mg Ba/L). The analytically determined test substance concentrations ranged between 80% and 120% of the nominal substance concentrations. The evaluation was therefore based on the nominal substance concentrations. The algal growth rate was affected by barium bis(dihydrogenorthophosphate). After 72 hours an EC50 of 6.07 mg/L (nominal) was determined. The determined NOEC is 2.5 mg/L (nominal) based on the algal growth rate.