Titanium oxide sulphate

Toxicity to terrestrial plants

Administrative data

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

2008-02-19 to 2008-04-16; repeat barley assay: 2008-05-05 to 2008-05-26

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Valid and conclusive guideline study according to generally accepted standards. Test item was titanium dioxide, which is considered the relevant transformation product of target substance titanium oxide sulphate when in contact with humidity.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: ISO 11269-2 protocol

GLP compliance:

no

Remarks:

Compliance statement to ISO 11269-2 protocol attached (see below)

Test material

Test material information

Constituent 1

Reference substance name:

Slags, ilmenite electrothermal smelting

EC Number:

293-671-6

EC Name:

Slags, ilmenite electrothermal smelting

Cas Number:

91081-64-0

IUPAC Name:

293-671-6

Details on test material:

Upgraded ilmenites (UGI) consist primarily (> 80%) of a titanate phase i.e., Ti (as TiO2) with Fe, Al, Si, Mg and other metals. As the mineral, ilmenite generally contains 55-65% titanium as TiO2 ( Rutile and ilmenite - Australian production and potential profile. http://www.chemlink.com.au/titan_rutile.htm ), the read across bases on the assumption of 60% weight titanium dioxide.

- Molecular formula (as other than submission substance): TiO2
- Molecular weight (as other than submission substance): 79.899 g/mol
- Smiles notation (as other than submission substance): [Ti](=O)=O
- InChl (as other than submission substance): InChI=1/2O.Ti/rO2Ti/c1-3-2
- Structural formula attached as image file (as other than submission substance): O=Ti=O
- Name of test material (as cited in study report): Exxaro SO4 and RBM SO4

Exxaro SO4: Sulphate Slag Marketing Sample MKT_SUL_070624_0000, 'slag 1'
RBM SO4: 'slag2'
- Justification: Based on the preliminary results of the Folsomia candida test, upgraded ilmenite (UGI) products with the lowest and the highest effects (Exxaro SO4 and RBM SO4, respectively) were selected to perform further ecotoxicity testing

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
JUSTIFICATION FOR READ ACROSS
In the present study the soil was spiked with the test surrogate ilmenite (CAS 91081-64-0). The mineral contains 55-65% titanium as TiO2, the rest being iron oxide. Titanium dioxide is considered the relevant transformation product of target substance titanium oxide sulphate when in contact with humidity. As the other final hydrolysis product sulphuric acid dissociates fully at around neutral pH, the substance itself will not reach the terrestrial environment except via direct exposure, which is not expected in quantities exceeding the soil buffering capacity. Sulphate is non-toxic and with regard to the rather high natural background concentrations irrelevant.

Upgraded ilmenites (UGI) consist primarily (> 80%) of a titanate phase i.e., Ti (as TiO2) with Fe, Al, Si, Mg and other metals. Transformation/dissolution tests were performed with UGI products by analysing total dissolved concentrations of the trace and minor elements Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Nb, Ti, V and Zn over periods up to 28 days at loadings of 100, 10 and 1 mg/L. The T/D data revealed that only Fe, Mn and V among the 12 metals dissolved to any significant extent (maximum increase in Fe, Mn and V concentrations 26.2, 8.9 and 3.5 µg/l, respectively). Within the limits of experimental error, the other metals remained refractory to release, none dissolving from any of the slags at any of the loadings. Because of the structural similarity and the low solubility of both UGI slags and TiO2, read-across for ecotoxicological hazard data from UGI to TiO2 is considered relevant.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Pore water from the control and the 1 and 10% slag dosed soils was collected in duplicate of the lettuce grown soils and of the NPK enriched barley grown soil

Test substrate

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil (if used): Slags were added to soils on 17th of March 2008 by weighing the appropriate amount of air dry soil and slag (0, 0.03, 0.1, 0.3, 1, 3 and 10 wt%) and mixing in a clean concrete mixer to a final total amount of 4292 g dry matter. The soil/slag mixture was homogenized for 5 minutes, and stored in plastic bags till use. All treated soils were moistened at the same time (26th of March 2008) to 18.5% moisture content by adding deionised water and mixing manually. A 144 g subsample was set apart for the soil nitrification test.

Test organisms

1

Species:

Hordeum vulgare

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: summer barley

2

Species:

Lactuca sativa

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: lettuce

Study design

Test type:

other: seedling emergence and shoot yield (dry)

Study type:

laboratory study

Substrate type:

other: Ter Munck soil (agricultural)

Limit test:

no

Total exposure duration:

20 d

Post exposure observation period:

Plants were harvested 20 days after sowing (i.e. 17 days after emergence of the control seedlings), and the fresh plant yield per pot was determined. Plants were dried at 70°C for 16 h and the dry plant yield per pot was determined.

Test conditions

Test temperature:

Air temperatures in the cabinet were 20°C (day) and 16°C (night)

pH:

Exxaro SO4: 7.00
RBM SO4: 7.00 (Preliminary experiments showed that the addition of slag2 to soil acidified the soil by 0.6-0.7 pH units, and that this pH decrease can be neutralized by adding 10 mmol OH--equivalents per kg dry soil. Therefore, a ‘slag+CaO’ treatment was included for the soil amended with 1 and 10% of slag 2 that received an extra 5 mmol CaO/kg (corresponding to 1.2 g CaO powder) on top of the pure slag to compensate for the pH drop)

Moisture:

The soils for the plant growth tests were moistened to 23.5% moisture content (pF2) and mixed manually.

Details on test conditions:

TEST SYSTEM
- Testing facility: growth cabinet (Weiss, 18' SP/+5 JuPa)
- Test container (type, material, size): plastic pots with a top diameter of 95 mm of which the bottom was perforated and covered with a filter cloth (mesh size 140-150 µm)
- Amount of soil: eight 600 g fresh soil subsamples (4 replicates for each plant)
- Method of seeding: 10 seeds of both species were uniformly sown on top of the soil (lettuce) or 0.5-1 cm under the soil surface (summer barley)
- No. of plants (retained after thinning): 5 seedlings per pot
- No. of replicates per treatment group: 4
- No. of replicates per control: 4


SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Heverlee, Belgium
- Pesticide use history at the collection site: no data
- Collection procedures: no data
- Sampling depth (cm): no data
- Soil texture (if natural soil)
- % sand: 10
- % silt: 76
- % clay: 14
- Soil taxonomic classification: Haplic Luvisol with a silt-loam texture
- Soil classification system: WRB soil classification
- Organic carbon (%): 0.93
- Total N (%): 0.08
- Water holding capacity (in ml/100g dry soil): 43.4
- Bulk density (g/cm3): 1.38
- Water content at pF2 (100 cm suction) (ml/100g dry soil): 28.9
- eCEC: 9.8 cmol/kg
- Ammonium oxalate extractable Al, Fe and Mn oxides:
Feox (mg/kg): 2021
Alox (mg/kg): 536
Mnox (mg/kg): 254
- Aqua regia extractable metals:
Cd (mg/kg): 0.3
Cu (mg/kg): 18.5
Co (mg/kg): 6.6
Ni (mg/kg): 13.1
Pb (mg/kg): 26.4
Zn (mg/kg): 52.2
Sb (mg/kg): 0.6
- Pretreatment of soil: soil was immediately air dried at 25°C for 8 days and sieved (4 mm)
- Storage (condition, duration): the air-dried soil was stored in plastic bags at room temperature


NUTRIENT MEDIUM (if used)
- Description: for barley the shoot yield test was repeated (due to symptoms as leaves that turned yellowish/brownish indicating a lack of nutrients tosupport healthy growth) with soil that was remoistened with NPK enriched water (4.81 g KNO3 and 1.462 g KH2PO4 per l) to obtain a final concentration of 100 mg N and 50 mg P per kg dry soil


GROWTH CONDITIONS
- Photoperiod: 16 h/8 h day/night cycle
- Light intensity and quality: light intensity at canopy hight was 650 µmol photons/m2/s
- Day/night temperatures: 20°C (day), 16°C (night)
- Relative humidity (%): 70%
- Watering regime and schedules: the soil surface was covered with sixty grams of polyethylene beads to reduce evaporation; water loss of the pots was restored daily with deionised water

Nominal and measured concentrations:

Nominal concentrations (weight %): 0; 0.03; 0.1; 0.3; 1; 3; 10
Measured (mg/L): <0.01

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Species:

Hordeum vulgare

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 g/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Exxaro SO4 and RBM SO4

Basis for effect:

seedling emergence

Remarks on result:

other: 10% weight, corresponds to 0.75 mol TiO2/kg soil dw; TiO2 regarded to represent 60% of the mass = 60 g/kg soil dw

Effect concentrations 2

Species:

Hordeum vulgare

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 g/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Exxaro SO4 and RBM SO4

Basis for effect:

growth

Remarks:

shoot yield (dry)

Remarks on result:

other: 10% weight, corresponds to 0.75 mol TiO2/kg soil dw; TiO2 regarded to represent 60% of the mass = 60 g/kg soil dw

Effect concentrations 3

Species:

Lactuca sativa

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 g/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Exxaro SO4 and RBM SO4

Basis for effect:

seedling emergence

Remarks on result:

other: 10% weight, corresponds to 0.75 mol TiO2/kg soil dw; TiO2 regarded to represent 60% of the mass = 60 g/kg soil dw

Effect concentrations 4

Species:

Lactuca sativa

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 100 g/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

Exxaro SO4 and RBM SO4

Basis for effect:

growth

Remarks:

shoot yield (dry)

Remarks on result:

other: 10% weight, corresponds to 0.75 mol TiO2/kg soil dw; TiO2 regarded to represent 60% of the mass = 60 g/kg soil dw

Effect concentrations 5

Species:

Lactuca sativa

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 202 g/kg soil dw

Nominal / measured:

estimated

Conc. based on:

other: target compound titanium oxide sulphate

Basis for effect:

other: seedling emergence and growth shoot yield (dry)

Remarks on result:

other: Converted from 0.75 mol/kg soil dw on the basis of MW TiOSO4 = 159.93 g/mol

Effect concentrations 6

Species:

Hordeum vulgare

Duration:

20 d

Dose descriptor:

NOEC

Effect conc.:

>= 202 g/kg soil dw

Nominal / measured:

estimated

Conc. based on:

other: target compound titanium oxide sulphate

Basis for effect:

other: seedling emergence and growth shoot yield (dry)

Remarks on result:

other: Converted from 0.75 mol/kg soil dw on the basis of MW TiOSO4 = 159.93 g/mol

Any other information on results incl. tables

Exxaro SO4:

Pore water composition of soil samples used for lettuce growth test:

Sample	Ca (mg/L)	Mg (mg/L)	K (mg/L)	Na (mg/L)	S (mg/L)	Ti (mg/L)
Control	28.5	2.4	5.1	0.8	9.9	<0.01
Exxaro 1%	51.2	4.5	6.3	3.7	42.4	<0.01
Exxaro 10%	273.6	25.2	11.6	27.7	183.3	<0.01

Pore water composition of soil samples used for barley growth test:

Sample	Ca (mg/L)	Mg (mg/L)	K (mg/L)	Na (mg/L)	S (mg/L)	Ti (mg/L)
Control	152.6	14.3	70.1	17.1	2.7	<0.01
Exxaro 1%	239.3	22.9	95.9	22.0	6.7	<0.01
Exxaro 10%	312.2	28.2	97.8	42.1	115.7	<0.01

The difference in concentrations of Ca, Mg, Na and K in control treatment for barley growth test and lettuce growth test are due to fertilisation with K and subsequent replacement of Ca, Mg and Na from exchange complex by K-ions.

Addition of the slags at the highest doses (>1%) results in increased Ca, Mg, K, Na and S concentrations in pore water. However, the Ti concentration is still below the detection limit, even at the highest dose added (10%).

RBM SO4:

Pore water composition of soil samples used for lettuce growth test:

Sample	Ca (mg/L)	Mg (mg/L)	K (mg/L)	Na (mg/L)	S (mg/L)	Ti (mg/L)
Control	28.5	2.4	5.1	0.8	9.9	<0.01
RBM 1%	64.3	5.6	12.2	<0.1	60.9	<0.01
RBM 10%	411.6	44.0	13.4	17.0	199.9	<0.01

Pore water composition of soil samples used for barley growth test:

Sample	Ca (mg/L)	Mg (mg/L)	K (mg/L)	Na (mg/L)	S (mg/L)	Ti (mg/L)
Control	152.6	14.3	70.1	17.1	2.7	<0.01
RBM 1%	138.3	12.4	81.0	17.5	6.3	<0.01
RBM 10%	496.3	50.7	132.7	29.3	173.8	<0.01

The difference in concentrations of Ca, Mg, Na and K in control treatment for barley growth test and lettuce growth test are due to fertilisation with K and subsequent replacement of Ca, Mg and Na from exchange complex by K-ions.

Addition of the slags at the highest doses (>1%) results in increased Ca, Mg, K, Na and S concentrations in pore water. However, the Ti concentration is still below the detection limit, even at the highest dose added (10%).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The test article exhibited no phytotoxic activity to terrestrial plants exposed via soil

Executive summary:

The toxicity of upgraded ilmenites (UGI) to terrestrial plants, i.e. the monocot summer barley (Hordeum vulgare) and the dicot lettuce (Lactuca sativa) was studied in a dose response test according to the ISO 11269-2 protocol. No formal GLP applied, but due to the sufficient documentation the experiment is considered valid and conclusive. In the present study the soil was spiked with the tet surrogate ilmenite. The test article consist primarily (> 80%) of a titanate phase i.e. titanium dioxide with Fe, Al, Si, Mg and other metals. As the slag contains almost titanium dioxide, which is the substance formed by hydrolysis of target compound titanium oxide sulphate, the experiment is considered usable for read across. Recalculation of the measured values was made on an isomolar basis as the test surrogate results from isomolar transformation of the target chemical.

The test item was applied in nominal concentrations of 0 (control), 0.03, 0.1, 0.3, 1, 3, and 10% corresponding to 0.3, 1, 3, 10, 30, and 100 g ilmenite/kg soil dw. No analytical dose verification was performed. The test organisms were during 20 days exposed to the slag mixed into soil and the endpoints seedling emergence and growth, i.e. shoot yield (dry) were recorded.

Even in the highest concentration of 10% weight, corresponding to 0.75 mol TiO2/kg soil dw or, as TiO2 represents about 60% of the mass, 60 g/kg soil dw no effect was observable. Thus the applied concentration is considered a NOEC with no corresponding LOEC. On the basis of the molar test article concentration the level for the target compound titanium oxide sulphate was assessed to ≥ 202 g/kg soil dw. No threshold concentration can be derived.

In conclusion the test article exhibited no phytotoxic activity to terrestrial plants exposed via soil.