Diiron magnesium tetraoxide

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

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 VII, Column 2, Section 9.1.1. of Regulation (EC) 1907/2006, testing for short-term toxicity on invertebrates 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”.

Magnesium ferrite 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 transformation/dissolution data (Klawonn, 2018) that indicate a very low release of pigment components at pH 6 and 8. Transformation/dissolution tests of Magnesium ferrite at a loading of 1 mg/L and pH 6 resulted after 7 days in iron concentrations below the LOD of 0.3013 µg Fe/L and zinc concentrations of 2.746 µg Zn/L. After 28 days T/D tests at pH 6, the iron and zinc concentrations remained below the respective LOQs of 0.9039 µg Fe/L and 0.445 µg Zn/L. T/D tests at a loading of 1 mg/L and pH 8 for 7 and 28 days resulted in dissolved iron and zinc concentrations below the respective LODs of 0.1851 µg Fe/L and 0.0411 µg Zn/L. 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”. Further, “Where the chronic ERV for the metal ions of concern is greater than 1 mg/L, the metals need not be considered further in the classification scheme”. Accordingly, magnesium was not considered in the T/D assessment since it does not have an ecotoxic potential as confirmed by ecotoxicity reference values of > 1 mg Mg/L listed in the Metals classification tool (MeClas) database. Thus, the rate and extent to which Magnesium ferrite produces soluble (bio)available ionic and other iron- and zinc-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 Magnesium ferrite is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for Magnesium ferrite. The poorly soluble substance Magnesium ferrite 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. The acute ERVs are based on the lowest EC50/LC50 values for algae, invertebrates and fish and were obtained from the Metals classification tool (MeClas) database as follows: An acute ERV for magnesium has not been derived since a concern for short-term (acute) toxicity of magnesium ions was not identified. The acute ERV of iron (>100 mg Fe/L) is above 1 mg/L and a concern for short-term (acute) toxicity was not identified (no classification). 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.” The acute ERVs for zinc are 413 µg Zn/L at pH 6 and 136 µg Zn/L at pH 8 and thus well above the dissolved zinc concentrations of 2.746 µg Zn/L at pH 6 and < 0.0411 µg Zn/L at pH 8, determined after 7 days T/D tests at loading of 1 mg/L. Due to the lack of an acute aquatic hazard potential for soluble iron and magnesium ions and the fact that the dissolved zinc concentrations determined after 7 days T/D tests at pH 6 and 8, are significantly lower than the respective lowest short-term ERVs for zinc, it can be concluded that the substance Magnesium ferrite 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 Magnesium ferrite is poorly soluble and does not meet classification criteria for acute (short-term) aquatic hazard.

Magnesium ferrite is poorly soluble and unlikely to cross biological membranes. In accordance with Annex VII, Column 2, Section 9.1.1. of Regulation (EC) 1907/2006, testing for short-term toxicity to invertebrates is not necessary.

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:

2015-05-06 to 2015-06-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

Version / remarks:

2001

GLP compliance:

yes (incl. QA statement)

Type of method:

other: transformation/ dissolution

Key result

Type of test:

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

Mean dissolved conc.:

< 0.904 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least

Key result

Type of test:

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

Mean dissolved conc.:

< 0.301 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Type of test:

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

Mean dissolved conc.:

< 0.301 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Key result

Type of test:

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

Mean dissolved conc.:

< 0.185 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Key result

Type of test:

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

Mean dissolved conc.:

< 0.185 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other:

Type of test:

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

Mean dissolved conc.:

< 0.555 µg/L

Element analysed:

Fe

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least

Key result

Type of test:

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

Mean dissolved conc.:

< 0.445 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: at least < LOQ (<0.4446)

Key result

Type of test:

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

Mean dissolved conc.:

2.746 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 0.241 µg/L

Type of test:

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

Mean dissolved conc.:

1.537 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: SD: ± 1.448 µg/L

Key result

Type of test:

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

Mean dissolved conc.:

< 0.041 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

672 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: < LOD (<0.0411)

Key result

Type of test:

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

Mean dissolved conc.:

< 0.041 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

168 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Remarks on result:

other: < LOD (<0.0411)

Type of test:

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

Mean dissolved conc.:

0.209 µg/L

Element analysed:

Zn

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, agitation at 100 rpm, 21.5 ± 1.5 °C

Details on results:

Temperature
The temperature of the thermostatically controlled room was recorded with a Testo 175-T2 data logger. The mean temperature was 20.3 ± 0.3 °C during the test with 1 mg/L loading at pH 6 and 20.4 ± 0.2 °C during the test at pH 8. Therefore, the mean temperature is in agreement with the OECD guidance document 29.

Solution pH and oxygen concentrations
In solutions containing 1 mg/L of the test item at pH 6 and pH 8 as well as in method blanks (BW), the pHs were in the range of 5.8 – 6.6 and 7.4 – 8.1, respectively

Mass balance
The measured iron concentrations in samples with test item were mostly below respective LODs/LOQs or slightly above. Therefore, these amounts of iron were not considered for calculation of mass balance. The recovery was 21.4 % - 61.0 % for pH 6 and 42.0 – 51.4 % for pH 8., indicating that aqua regia is not sufficient for a complete dissolution of the test item. This is expected for inorganic pigments.

Within-vessel variation and between-vessel variation
According to the guidance, “[…]it is reasonable to anticipate that for a constant loading of a substance, tested in a narrow particle size (e.g. 37 - 44 μm) and total surface area range, the within-vessel variation in transformation data should be less than 10 % and the between-vessel variation should be less than 20 %”.
The particle size distribution of each loading replicate may differ and thus resulting in different overall total surface areas per vessel. Since the exposed surface area is affecting the rate of transformation and dissolution of sparingly soluble metal compounds, increases in vessel variations may be observed in tests of materials with wider particle size distributions.
For the measured iron and zinc concentrations these variations are mostly not within the limits
Background concentrations for zinc at pH 6 and pH 8 were measured to be in the range of test item loaded samples. Therefore, the measured concentrations from test item loaded vessels at pH 6 and 8 were background (means) corrected. The background concentration of iron was below the LOD.

Method validation summary

Validation parameter	Results	Comment
selectivity	selective wavelength and isotopes for detection and evaluation of Fe and Zn
linearity	applied calibration functions were linear	correlation factor at least 0.999961
limit of detection	Fe: 0.1216 – 0.7443 µg/L Zn: 0.0149 – 0.1482 µg/L
limit of quantification	Fe: 0.3647 – 2.2298 µg/L Zn: 0.0448 – 0.4446 µg/L
accuracy and precision	Mean recovery for TM-25.4 1st series: Fe (259.940 nm): 94.6 ± 1.6 % (n = 10) Zn (213.857 nm): 103.1 ± 1.8 % (n = 10) 2nd series: Fe (240.489 nm): 92.2 ± 2.7 % (n = 4) 3rd series: Fe (259.940 nm): 113.9 ± 39.8 % (n = 11) Zn (202.548 nm): 98.9 ± 3.4 % (n = 11) 4th series: Fe (239.563 nm): 108.2 ± 23.5 % (n = 4) 5th series: Fe (259.940 nm): 103.1 ± 21.7 % (n = 7) Zn (202.548 nm): 99.6 ± 2.7 % (n = 7)	Diluted (5 fold) to 6.2 μg Fe/L, 8.9 μg Zn/L Due to ubiquitous Fe a slight contamination cannot be excluded for two samples from 3rd series, one sample from 4th series and one sample from 5th series. These are not within 100 ± 15 % resulting in these standard deviations. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for TMDA-53.3 2nd series: Fe (240.489 nm): 100.8 ± 1.9 % (n = 4) 3rd series: Fe (259.940 nm): 110.1 ± 39.7 % (n = 11) Zn (202.548 nm): 96.3 ± 1.1 % (n = 11) 4th series: Fe (239.563 nm): 103.6 ± 7.1 % (n = 4) 5th series: Fe (259.940 nm): 99.6 ± 5.1 % (n = 7) Zn (202.548 nm): 102.5 ± 11.1 % (n = 7)	Diluted (10 fold) to 32.5 μg Fe/L, 38.5 μg Zn/L The increased standard deviation in the 3rd series for Fe might be due to a contamination with ubiquitious Fe; one sample is not within 100 ± 15 %. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for TMDA-53.3 1st series: Fe (259.940 nm): 97.9 ± 1.1 % (n = 10) Zn (213.857 nm): 102.4 ± 1.0 % (n = 10)	Diluted (5 fold) to 65 μg Fe/L, 77.2 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC 1st series: Fe (259.940 nm): 95.5 ± 1.8 % (n = 10) Zn (213.857 nm): 92.4 ± 2.1 % (n = 10) 2nd series: Fe (240.489 nm): 98.5 ± 2.0 % (n = 4)	Diluted to 10 μg Fe/L, 10 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC1 3rd series: Fe (259.940 nm): 96.6 ± 0.9 % (n = 8); Zn (202.548 nm): 95.4 ± 1.6 % (n = 8) 4th series: Fe (239.563 nm): 97.3 ± 2.1 % (n = 4) 5th series: Fe (259.940 nm): 95.8 ± 2.1 % (n = 7); Zn (202.548 nm): 92.4 ± 2.4 % (n = 7)	Diluted to 10 μg Fe/L, 10 μg Zn/L
accuracy and precision	Mean recovery for quality control standard QC1 3rd series: Fe (259.940 nm): 97.2 ± 0.6 % (n = 2) Zn (202.548 nm): 95.1 ± 0.3 % (n = 3)	Diluted to 100 μg Fe/L, 100 μg Zn/L In the 3rd series one sample with a recovery of 428 % regarding Fe is rejected because this can assigned to a Fe contamination. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for recalibration standard 1st series: Fe (259.940 nm): 94.7 ± 10.6 % (n = 10) Zn (213.857 nm): 104.0 ± 44.4 % (n = 10) 2nd series: Fe (240.489 nm): 91.2 ± 3.9 % (n = 4) 3rd series: Fe (259.940 nm): 101.8 ± 6.0 % (n = 8) Zn (202.548 nm): 85.7 ± 1.0 % (n = 8) 4th series: Fe (239.563 nm): 95.9 ± 2.0 % (n = 4) 5th series: Fe (259.940 nm): 99.7 ± 2.6 % (n = 7) Zn (202.548 nm): 104.2 ± 10.9 % (n = 7)	Diluted to 5 μg Fe/L, 5 μg Zn/L The increased standard deviation in the 5th series for Zn might be due to a contamination with ubiquitous Zn; one sample is not within 100 ± 15 %. Not critical > 60% of all QA/QC samples are within these limits.
accuracy and precision	Mean recovery for recalibration standard 3rd series: Fe (259.940 nm): 97.7 ± 0.6 % (n = 3) Zn (202.548 nm): 94.3 ± 0.3 % (n = 3)	Diluted to 50 μg Fe/L 50 μg Zn/L
trueness	Mean recoveries of fortified samples: Fe: 81.8 – 109.6 % Zn: 84.0 – 164.9 %	In sample fortification from the 1st and the 5th measurement series there was obviously a mistake in sample preparation because the recoveries are not all within 100 ± 15 %. This is not critical, the series are valid because > 60 % of all QA/QC samples are within these limits. This approach is according to internal SOPs for GLP and accreditation according to ISO 17025

Recoveries of fortified samples Iron (values were rounded, internal calculations were performed with more digits)

	measured Fe [μg/L]	calculated Fe after addition [μg/L]	Recovery [μg Fe/L]	Recovery [%]
1st series 1 mL of sample + 4 mL of 5 μg Fe/L
vessel 4, sample a after 2h	<LOD	4.000	4.148	103.7
vessel 4, sample a after 6h	<LOD	4.000	4.255	106.4
vessel 4, sample a after 1d	<LOD	4.000	4.305	107.6
vessel 4, sample a after 4d	<LOQ	4.000	4.214	105.3
vessel 4, sample a after 7d	<LOD	4.000	4.127	103.2
vessel 4, sample a after 14d	0.914	4.183	4.583	109.6
vessel 4, sample a after 21d	<LOQ	4.000	4.266	106.7
vessel 4, sample a after 28d	<LOD	4.000	4.182	104.6
2nd series 2 mL of sample + 3 mL of 75 μg Fe/L
vessel 4	95.64	83.254	84.302	101.3
4th series 2 mL of sample + 3 mL of 75 μg Fe/L
vessel 1	201.213	60.243	61.925	102.8
5th series 1 mL of sample + 4 mL of 50 μg Fe/L
vessel 1, sample a after 2h	1.595	40.319	34.124	84.6
vessel 1 sample a after 6h	<LOD	40.000	33.185	83.0
vessel 1, sample a after 1d	<LOQ	40.000	32.902	82.3
vessel 1, sample a after 4d	<LOQ	40.000	32.991	82.5
vessel 1, sample a after 7d	22.402	44.480	36.867	82.9
vessel 1, sample a after 14d	<LOD	40.000	32.735	81.8
vessel 1, sample a after 21d	<LOD	40.000	32.923	82.3
vessel 1, sample a after 28d	<LOD	40.000	32.895	82.2

Recoveries of fortified samples Zinc (values were rounded, internal calculations were performed with more digits)

	measured Zn [μg/L]	calculated Zn after addition [μg/L]	Recovery [μg Zn/L]	Recovery [%]
1st series 1 mL of sample + 4 mL of 5 μg Zn/L
vessel 4, sample a after 2h	1.217	4.243	6.706	158.0
vessel 4, sample a after 6h	1.539	4.308	6.921	160.7
vessel 4, sample a after 1d	1.881	4.376	7.012	160.2
vessel 4, sample a after 4d	1.449	4.290	6.860	159.9
vessel 4, sample a after 7d	1.564	4.313	6.884	159.6
vessel 4, sample a after 14d	2.386	4.477	7.381	164.9
vessel 4, sample a after 21d	2.911	4.582	6.984	152.4
vessel 4, sample a after 28d	2.716	4.543	7.245	159.5
5th series 1 mL of sample + 4 mL of 50 μg Zn/L
vessel 1, sample a after 2h	2.110	40.422	34.249	84.7
vessel 1 sample a after 6h	1.360	40.272	34.518	85.7
vessel 1, sample a after 1d	0.696	40.139	34.015	84.7
vessel 1, sample a after 4d	1.244	40.249	34.118	84.8
vessel 1, sample a after 7d	2.573	40.515	34.258	84.6
vessel 1, sample a after 14d	1.752	40.350	33.981	84.2
vessel 1, sample a after 21d	10.927	42.185	34.295	81.3
vessel 1, sample a after 28d	1.767	40.353	34.261	84.9

Conclusions:

The transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001) of "Magnesium ferrite " at a loading of 1 mg/L at pH 6 and 8, performed for 28d, resulted in Fe concentrations below the LOD/LOQ and maximum Zn concentrations of 2.75 µg/L (pH = 6, 7d). Thus, the extent to which "Magnesium ferrite " can produce soluble available ionic and other metal-bearing species in aqueous media is limited.