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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
2 Nov 2009 - 5 Nov 2009
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Preparation of test solutions for the final test started with loading rates of 1.0, 10 and 100 mg/L applying a two-day period of magnetic stirring followed by an overnight stabilisation period. The obtained solutions still contained undissolved material in the form of a floating layer and precipitate. The aqueous phase of each solution was carefully siphoned.
- Differential loading: yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: NIVA CHL 1
- Source: In-house laboratory culture.

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
21.9 and 23.8 °C
pH:
8.1 - 8.6
Nominal and measured concentrations:
WAFs prepared at loading rates of 1.0, 10 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 100 mL, all-glass, containing 50 mL of test solution
- Initial cells density: 1 x 10E4 cells/mL
- No. of vessels per concentration (replicates): 6 replicates of the highest concentration and 3 replicates of each lower test concentration. 1 replicate of each test concentration without algae.
- No. of vessels per control (replicates): 6 replicates of the control.

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: According to guideline (M2)


OTHER TEST CONDITIONS
- Photoperiod: Continuously
- Light intensity and quality: TLD-lamps of the type ‘Cool-white’ of 30 Watt, with a light intensity within the range of 73 to 86 µE.m-2.s-1.


EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: At the beginning of the test, cells were counted using a microscope and a counting chamber. Thereafter cell densities were determined by spectrophotometric measurement of samples at 720 nm using a Varian Cary 50 single beam spectrophotometer with a cuvette (pathlength = 10 mm). At the end of the final test microscopic observations were performed to verify a normal and healthy appearance of the inoculum culture and to observe for any abnormal appearance of the algae.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
- Results with reference substance valid? yes

Potassium dichromate reduced growth rate of this fresh water algae species at nominal concentrations of 1.0 mg/L and higher.

The EC50 for growth rate reduction (ERC50: 0-72h) was 1.6 mg/L with a 95% confidence interval ranging from 1.1 to 2.3 mg/L. The historical ranges for growth rate reduction lie between 0.82 and 2.3 mg/L. Hence, the ERC50: 0-72h for the present batch corresponds with this range.

The EC50 for yield inhibition (EYC50: 0-72h) was 0.62 mg/L with a 95% confidence interval ranging from 0.50 to 0.78 mg/L. Historical ranges are not yet available.

Table 1. Effect parameter

Parameter

TOS/BEM 09-014

WAF1prep. at

(mg/L)

NOERL

100

72h-ERL50

> 100

NOEYL

100

72h-EYL50

> 100

CONCLUSION

No reduction of growth rate or inhibition of yield was recorded at any of the loading rates of
TOS/BEM 09-014 S1 tested.

 The EL50for both growth rate reduction (ERL50: 0-72h) and yield inhibition (EYL50: 0-72h) were beyond the range tested, i.e. exceeded a loading rate of 100 mg/L.

The NOEL for both the growth rate reduction and yield inhibition equalled a WAF prepared at a loading rate of 100 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
No reduction of growth rate could be determined up to a loading rate of 100 mg/L. The test substance is neither acute nor chronic toxic to algae.

Description of key information

Cenospheres are not harmful to algae

Key value for chemical safety assessment

Additional information

One study (Migchielsen, 2010) according to OECD 201 is used as key study. The tested fly ash was structural related to ash (residues), cenospheres and as cenospheres are a component of fly ash, these results can be used as read across.

Under static test conditions algae were exposed to a series of water accommodated fractions up to a loading rate of 100 mg/L. Algal growth was assessed by spectrophotometric measurements at 24 h intervals. No reduction of algal growth or inhibition of yield compared to the control could be observed during an exposure period of 72 h. The EL50 could not be determined as they were beyond the range tested, exceeding a loading rate of 100 mg/L. NOEL for all ashes equalled a loading rate of 100 mg/L. Based on these findings the substance is not to be harmful to algae and it can be concluded that cenospheres are also not harmful to algae.

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