Triiron tetraoxide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

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 211 (Daphnia magna Reproduction Test)

Version / remarks:

1998

Principles of method if other than guideline:

A chronic study was performed according to the OECD Guideline 211 to assess the potential effects of nano-Fe2O3 at concentrations of 8.2-20 mg/L on the reproduction of Daphnia magna. Offspring production and mortality were observed over the 21 d exposure period. Deviations from the standard guideline were not reported.

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):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Feeding during test: Yes
- Food type: Green algae Raphidocelis subcapitata
- Amount: 3×10^5 cells/mL
- Frequency: Every other day from renewal of the culture medium

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

not reported

Test temperature:

20±2°C

pH:

not reported

Dissolved oxygen:

not reported

Conductivity:

not reported

Nominal and measured concentrations:

Nominal: 0 (control), 8.19, 10.24, 12.8, 16.0, and 20.0 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL glass vials
- Fill volume: 25 mL
- Renewal rate of test solution: Every second day
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 12
- No. of vessels per control (replicates): 12

TEST MEDIUM / WATER PARAMETERS
- Medium: Synthetic ASTM hard water medium (ASTM, 1980)

OTHER TEST CONDITIONS
- Photoperiod: 16:8 h (light:dark)

EFFECT PARAMETERS MEASURED: Animals were observed daily for offspring production and mortality. After 21 days exposure, fecundity was determined as the total number of neonates released per female.

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 20 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Reported statistics and error estimates:

One-way ANOVAs followed by Dunnett tests were employed to find out potential significant differences in the endpoints assessed between the control and tested concentrations, using the software Sigmaplot version 11.0 (Zar 1996). 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 ASTM water

Conc. (mg/L)	Soluble metal ions (mg/L)	pH	Zeta potential	Cond (mS/cm)	Z average diameter (nm)	Average diameter by number distribution	PdI
20	9.17 ± 0.07	8.91	-21.4 ± 5.9	0.566 ± 0.003	1830 ± 55	461 ± 64	0.764 ± 0.37

Validity criteria fulfilled:

yes

Remarks:

stated by the authors; mean number of living offspring per parent animal > 60

Conclusions:

A chronic toxicity study was performed according to OECD 211 to assess the potential effects of nano-Fe2O3 (average particle size 85×425 nm) at concentrations of 8.2-20 mg/L on the reproduction of Daphnia magna. No significant effect on the reproduction (number of offspring) of Daphnia magna was observed for Fe2O3 nanoparticles at the applied concentrations of 8.2 to 20.0 mg/L and thus an unbounded 21 d 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 expected to cause chronic toxicity to aquatic invertebrates. Effects of diiron trioxide nanoparticles on the reproduction of Daphnia magna were not observed in a reliable 21-d chronic toxicity study according to OECD 211 up to the highest test concentration of 20 mg/L and an unbounded NOEC of >= 20 mg/L was derived (Nogueira et al., 2015), a concentration that is twofold above the corresponding OECD test limit.

Additional information

A chronic toxicity study was performed by Nogueira et al. (2015) according to OECD 211 to assess the potential effects of nano-Fe2O3 (average particle size 85 × 425 nm) at concentrations of up to 20 mg/L on the reproduction of Daphnia magna, a concentration that is 2-fold above the corresponding OECD test limit for chronic toxicity. A significant effect on the reproduction (number of offspring) of Daphnia magna was not observed for Fe2O3 nanoparticles at the applied concentrations of 8.2 to 20.0 mg/L and thus an unbounded 21 d NOEC >= 20 mg/L (nominal) was derived.

 

Based on read-across to nano-sized iron (hydr)oxides (see attachment "Endpoint-specific read-across justification for the iron oxide category" in section 13), available data indicate a low potential for chronic toxicity of micro-sized iron (hydr)oxides to aquatic invertebrates (see table below).

 

Table: Chronic toxicity of iron (hydr)oxides to aquatic invertebrates.

Endpoint	Test species	Test results	Test material/form	Reliability: Reference
Long-term toxicity to aquatic invertebrates	Daphnia magna	NOEC (21d): >= 20 mg/L nominal	diiron trioxide / nano	RL2: Nogueira et al., 2015