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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:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Justification for type of information:
see attachment "Read-across justification-environ assessment-iron oxides" and “Endpoint-specific read-across justification for nano forms of iron oxide, 2021” attached in IUCLID section 13.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2006
Deviations:
yes
Remarks:
Performed in 24-well microplates
Principles of method if other than guideline:
A 72 h study according to OECD guideline 201 was conducted to evaluate the potential effects of nano-Fe2O3 on the growth of the green alga Raphidocelis subcapitata.
GLP compliance:
not specified
Remarks:
not specified in publication
Analytical monitoring:
yes
Details on sampling:
- Concentrations: Samples were taken from suspensions at the highest test concentration.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: NM suspensions were prepared by vigorously mixing the NM in the corresponding medium through magnetic stirring.
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Stock culture: Maintained in Woods Hole MBL growth medium at 20±2°C, under continuous
illumination (100 μE/m/s).
- Method of cultivation: According to OECD guideline 201 with adaptation to 24-well microplates.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not reported
Test temperature:
20±2°C
pH:
not reported
Dissolved oxygen:
not reported
Nominal and measured concentrations:
Nominal: 0, 8.2, 10.2, 12.8, 16.0, 20.0 mg Fe2O3-NPs/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 24-well microplates
- Volume: 1 mL
- Aeration: Twice a day by repetitive pipetting to promote active gas exchange and prevent cell clumping
- Initial cells density: 10^4 cells/mL

GROWTH MEDIUM
- Standard medium used: yes, OECD conform

OTHER TEST CONDITIONS
- Photoperiod: Continuous
- Light intensity and quality: 100 μE/m/s

EFFECT PARAMETERS MEASURED: Growth (photometric measurement of cell density at 440 nm absorbance)
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Reported statistics and error estimates:
The non-linear least squares regression procedure supplied by the software package Statistica 8.0 was used. One-way ANOVAs followed by Dunnett tests were also employed to find out potential significant differences in the endpoints assessed between the control and tested concentrations of each NM suspension, using the software Sigmaplot version 11.0. No observed effect concentration (NOEC) and low observed effect concentration (LOEC) values were taken from ANOVA significant results, reported for a significance level of 0.05.

Table 1: Data from DLS and ELS for Fe2O3 nanoparticles in MBL medium

Conc. (mg/L)

Soluble metal ions (mg/L)

pH

Zeta potential (mV)

Cond (mS/cm)

Z average diameter (nm)

Average diameter by number distribution

PdI

20

8.75±0.04

7.03

−22.9±8.4

0.537±0.007

1545±20

595±115

0.529±0.34

Validity criteria fulfilled:
yes
Remarks:
stated by the authors
Conclusions:
A 72 h algae growth inhibition test was performed according to OECD 201 to assess the potential effects of Fe2O3 nanoparticles (average particle size 85×425 nm). No significant effect on the growth rate of Pseudokirchneriella subcapitata was observed at the applied concentrations of 8.2 to 20.0 mg/L and thus an unbounded 72 h NOEC ≥ 20 mg/L (nominal) was derived.

Description of key information

Applying read-across to nano-sized iron (hydr)oxides (see attachment "Read-across justification-environ assessment-iron oxides" in section 13), micro-sized iron (hydr)oxides are not considered toxic to aquatic algae. In a reliable 72-h algae growth inhibition test according to OECD 201 with diiron trioxide nanoparticles, a significant effect on the growth rate of Pseudokirchneriella subcapitata was not observed at concentrations up to 20 mg/L and an unbounded 72 h NOEC >= 20 mg/L was derived (Nogueira et al., 2015).

Key value for chemical safety assessment

Additional information

A 72-h algae growth inhibition test was performed by Nogueira et al. (2015) according to OECD 201 to assess the potential effects of Fe2O3 nanoparticles (average particle size 85 × 425 nm). A significant effect on the growth rate of Pseudokirchneriella subcapitata was not observed at the applied concentrations ranging from 8.2 to 20.0 mg/L. Thus, an unbounded 72-h NOEC of ≥ 20 mg/L (nominal) and 72-h EC50 of > 20 mg/L were derived for the growth inhibition of P. subcapitata.

 

Based on read-across to nano-sized iron (hydr)oxides (see attachment "Read-across justification-environ assessment-iron oxides" in section 13), available data indicate a low potential for toxicity of micro-sized iron (hydr)oxides to aquatic algae (see table below).

 

Table: Toxicity of nano-sized iron (hydr)oxides to aquatic algae.

Endpoint

Test species

Test results

Test material/form

Reliability: Reference

Toxicity to aquatic algae and cyanobacteria

Pseudokirchneriella subcapitata

NOEC (72 h): >= 20 mg/L nominal

EC50 (72 h): > 20 mg/L nominal

diiron trioxide / nano

RL2: Nogueira et al., 2015