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Ecotoxicological information

Toxicity to terrestrial plants

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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:
key 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 with the test article titanium dioxide, which is considered the relevant transformation product for aquatic media

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2008
Report Date:
2008

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
other: ISO 11269-2 protocol
GLP compliance:
no
Remarks:
Compliance statement to ISO 11269-2 protocol attached (see below)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
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 analogue material ilmenite (CAS 91081-64-0). The mineral contains 55-65% titanium as TiO2, the rest being iron oxide. Titanium dioxide is exactly the substance formed by hydrolysis of the target chemical titanium tetrachloride (CAS 7550-45-0). As the additionally released hydrogen chloride fully dissociates in ions the substance self will not reach the sediment/terrestrial environment except via direct exposure, which is not expected in quantities exceeding the soil buffering capacity. The additional chlorine is nontoxic and with regard to the high natural background concentrations irrelevant. Thus additionally released hydrogen chloride should be disregarded.
In conclusion the test was conducted with the relevant transformation product.
Recalculation of the measured threshold values was made starting from 60% TiO2 on an isomolar basis as the analogue material results from isomolar transformation of the target chemical. The other constituents were treated as ineffective for effect level calculation.

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

open allclose all
Species:
Hordeum vulgare
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: summer barley
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 concentrationsopen allclose all
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
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
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
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
Species:
Lactuca sativa
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 142 g/kg soil dw
Nominal / measured:
estimated
Conc. based on:
other: target chemical titanium tetrachloride
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 TiCl4 = 189.712 g/mol
Species:
Hordeum vulgare
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 142 g/kg soil dw
Nominal / measured:
estimated
Conc. based on:
other: target chemical titanium tetrachloride
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 TiCl4 = 189.712 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 analogue material 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 (CAS 13463-67-7), which is exactly the substance formed by hydrolysis of the target chemical titanium tetrachloride (CAS 7550-45-0), the experiment is considered usable for read across. Recalculation of the measured values was made on an isomolar basis as the analogue material results from isomolar transformation of the target chemical and the iron dioxide was regarded ineffective.

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 chemical, titanium tetrachloride, was assessed to be = 142 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.