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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Sep.2014 - Nov.2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 26, 36.4, 51.0, 71.4 and 100 mg/L sampled at test start and test termination, respectively
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The text concentrations were prepared according to the OECD guidance documents No. 23 and 29. The Water Accommodated Faction (WAF) of the highest nominal test concentration was prepared by adding 199.9 mg test itemto 2 L sterile growth medium under sterile conditions. The mixture was stirred at 20°C for 24 hours and subsequently filtered. Further test concentrations were prepared by diluting the higest nominal test concentrations.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Source (laboratory, culture collection): SAG, Culture Collection of Algae at Pflanzenphysiologisches Institut of the University at Göttingen, Germany
- Method of cultivation: according to OECD guideline

ACCLIMATION
- Acclimation period: 3 days in standard OECD growth medium
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
22°C
pH:
7.06 - 8.04
Nominal and measured concentrations:
Nominal test substance concentrations: 26, 36.4, 51.0, 71.4 and 100 mg/L
Theoretical nominal boron loading: 2.65, 3.71, 5.20, 7.28 and 10.19 mg B/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass beakers (250 mL)
- Type: covered with air-permeable siliconesponge caps
- Material, fill volume: glass, 100 mL
- Initial cells density: 10000 cells/mL
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 8


GROWTH MEDIUM
- Standard medium used: yes TOECD standard medium according to OECD 201


OTHER TEST CONDITIONS

- Photoperiod: contnious illumination
- Light intensity and quality: 98.1 to 106.5 μmol/m s

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


TEST CONCENTRATIONS
:- Range finding study:yes, non-GLP
- Test concentrations: Nominal test loadings of 10.0, 31.6 and 100 mg test item/L
- Results used to determine the conditions for the definitive study: After 72 hours exposure the inhibition of growth rate was 2.6, -1.8, and 15.9 % at nominal test item loadings of 10.0, 31.6 and 100 mg/L. Respective inhibitions of yield were 11.3, -9.8, and 52.6 %.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1.35 other: mg boron/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 1.35 other: mg boron/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
No effects up to the highest test concentration
Results with reference substance (positive control):
Result of the routine sensitivity test with 3,5-dichlorophenol: ErC50: 3.78 mg/L (3.64-3.92 95% confidence limits)
Reported statistics and error estimates:
The EC values for growth rate and yield after 72 hours were not determined since there was no concentration-dependent inhibition > 50 %.
The NOEC values for growth rate and yield were determined by the Dunnett test using the computer program ToxRat® Professional.

Description of key information

Key value for chemical safety assessment

Additional information

The influence of Boron orthophosphate (CAS 13308-51-5) on growth of the uni-cellular freshwater green alga Pseudokirchneriella subcapitata was investigated in a static OECD 202 test under GLP conditions. Exponentially-growing cultures of the green alga were exposed to various concentrations of Boron orthophosphate over several generations under defined conditions for 72 hours. Since the test item is of low water solubility, the highest nominal test concentration was prepared following the Water Accommodated Faction (WAF) approach according to the OECD guidance documents No. 23 and 29 to obtain the maximal solubility of the test item under the test conditions. The algae were exposed to a series of dilutions obtained from a filtrated eluate of a 100 mg/L of loading. The media preparation was performed under sterile conditions.

For the determination of alga growth eight replicates of the control (test medium only) and four replicates of each test concentration were exposed to theoretical loadings of:

Nominal test item loadings: Control, 26, 36.4, 51.0, 71.4 and 100 mg/L, equivalent to theoretical nominal boron loading: Control, 2.65, 3.71, 5.20, 7.28 and 10.19 mg B/L.

The concentrations of boron in the test media were determined by chemical analyses in the aqueous phase at the start and at the end of the test using ICP-OES (LOQ 0.557 μg B/L).

At test start, the measured boron concentrations were 0.336, 0.475, 0.679, 0.968 and 1.35 mg/L (between 12.7 and 13.3 % of nominal loading). The boron concentrations were stable at all test substance concentrations throughout the test period (101 - 104 % compared to the measured initial concentrations). The test evaluation was based on the measured initial concentrations of boron due to the stability of the test item throughout the test, as well as on the nominal test substance concentration.

There were no concentration-dependent effects on the growth of the green alga up to the highest test concentrations of 1.35 mg boron/L. The ErC50 and EyC50 values for inhibition of growth rate and yield were set to be higher than the highest test concentration of 100 mg/L nominal.

The NOEC for both, growth rate and yield was ≥ 100 mg/L nominal test substance condition, corresponded to 1.35 mg boron/L (measured concentration).