High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix

Short-term toxicity to fish

Administrative data

Endpoint:

short-term toxicity to fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur

the study does not need to be conducted because the substance is unlikely to cross biological membranes, hence indicating that aquatic toxicity is unlikely to occur

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Annex VIII, Column 2, Section 9.1.3. of Regulation (EC) 1907/2006, the test for short-term toxicity on fish does not need to be conducted “if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water or the substance is unlikely to cross biological membranes”.

High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available transformation/dissolution data (Grané, 2010) that indicate a very low release of pigment components. Transformation/dissolution of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix (24-screening test according to OECD Series 29, loading of 100 mg/L, pH 6 and 8) resulted in mean dissolved iron concentrations of 0.131 µg/L Fe and 0.002 µg/L Fe, silicon concentrations of 215.7 µg/L Si and 204 µg/L Si at pH 6 and 8, respectively. Dissolution of iron and silicon is highest at pH 6, therefore pH 6 is considered as pH that maximised metal release. Metal release at the 1 mg/L loading and pH 6 remained below the respective LOD for iron and silicon (<0.22 µg/L Fe and <0.07 µg/L Si). After 28 days at the 1 mg/L loading and pH 6 iron concentrations of 0.29 µg/L were measured whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si). Thus, the rate and extent to which High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix produces soluble (bio)available ionic and other silicon- and iron-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix. The poorly soluble substance High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 days at a loading rate of 1 mg/L with the lowest acute ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions, respectively. The acute ERVs are based on the lowest EC50/LC50 values for algae, invertebrates and fish. Acute ERVs were obtained from the Metals classification tool (MeClas) database as follows: For iron ions, the acute ERV is above 1 mg/L (in fact above 100 mg/L) and a concern for short-term (acute) toxicity was not identified (no classification). An acute ERV for silicon has not been derived since a concern for short-term (acute) toxicity of silicon ions was not identified (see also OECD, 2004). According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “Where the acute ERV for the metal ions of concern is greater than 1 mg/L the metals need not be considered further in the classification scheme for acute hazard.” Due to the lack of an acute aquatic hazard potential for soluble silicon and iron ions and the fact that dissolved silicon and iron concentrations were below the LOD (<0.22 Fe and <0.07 µg/L Si) after 7 days at pH 6 in the T/D test, it can be concluded that the substance High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).

In accordance with Figure IV.4 “Classification strategy for determining acute aquatic hazard for metal compounds” of ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, the substance High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard.

High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is poorly soluble and unlikely to cross biological membranes. In accordance with Annex VIII, Column 2, Section 9.1.3. of Regulation (EC) 1907/2006, testing for short-term toxicity to fish is not necessary. Testing is also scientifically not justifiable for the reasons of animal welfare.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-08-03 to 2010-03-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

(a) the 28-day test with a loading of 1 mg/L was conducted at pH 6 instead of 5.5 (b) the within-vessel variation was not always < 10 % (c) `mass balance (%) after completion of the transformation test´ is missing.

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Deviations:

yes

Remarks:

please refer to the field "Rationale for reliability incl. deficiencies" above

GLP compliance:

yes

Type of method:

flask method

Remarks:

transformation/dissolution

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.002 µg/L

Element analysed:

Fe

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

0.131 µg/L

Element analysed:

Fe

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

204.019 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 8

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

215.745 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

24 h

Test conditions:

pH 6

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.734 µg/L

Element analysed:

Fe

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

T = 19.7 - 21.4 °C, pH = 6 ± 0.2

Remarks on result:

other: SD: ± 0.0828 µg/L

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

T = 19.7 - 21.4 °C, pH = 6.00 ± 0.2

Remarks on result:

other: < LOD

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.224 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

T = 19.7 - 19.9 °C, pH: 6.15

Remarks on result:

other: < LOD

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

T= 19.7 - 19.9 °C, pH= 6.15

Remarks on result:

other: < LOD

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.224 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

T = 19.7 - 21.2 °C, pH = 6.00 ± 0.2

Remarks on result:

other: < LOD

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

T = 19.7 - 21.2 °C, pH = 6.00 ± 0.2

Remarks on result:

other: < LOD

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

0.291 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

T = 19.7 - 22.4 °C, pH = 6.00 ± 0.2

Remarks on result:

other: SD: ± 0.0464 µg/L

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.069 µg/L

Element analysed:

Si

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

T = 19.7 - 22.4 °C, pH = 6.00 ± 0.2

Remarks on result:

other: < LOD

Details on results:

Silicium concentrations were below the detection limit in aqueous solutions with 1 mg/L and 100 mg/L loadings. Iron ions dissolved/transformed in aqueous solutions. At each time point dissolved Fe concentrations were < 1 μg/L.

Test conditions were predominantly in accordance with guideline:

- Vessel Variation:

The within-vessel variations from the 100mg/L loadings for selected vessels were >10 % (not guideline comform) due to concentrations being close to the LOQ. The between-vessel variation was always ≤ 20 %.

The within-vessel variations from the 1mg/L loading for selected vessels was >10 % (not guideline comform) due to concentrations being close to the LOQ. However, the between-vessel variation was always ≤ 20 % (guideline comform).

Oxygen:

- The oxgen concentrations were in the range of 4.7 and 9.7 mg/L with three values below the acceptable limit (>70 % of air O₂ concentration = 5.46 mg/L). However, a results-changing impact on dissolved Fe concentrations can be excluded.

Temperature:

- The temperature was in the range from 19.7 °C to 22.4 °C.

Solution pH:

- The pH was in the range of 6.05 to 6.19 (i.e. in the range of pH 6 + 0.2 units)

Conclusions:

The transformation/dissolution of the reaction mass of fumes, silica and diiron trioxide resulted in the following dissolved concentrations:

loading, Time Fe [µg/L] Si [µg/L]
1mg/L, 7 days < 0.22 (1mg/L, 28 days 0.29+/- 0.05 < 0.07 (100mg/L,7 days 0.73 +/- 0.08 < 0.07 (
As dissolved Fe and Si concentrations were below 1 µg/L even at the highest loading of 100 mg/L, the pigment can be considered environmentally inert.