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Ecotoxicological information

Toxicity to terrestrial plants

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Reference
Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
2008-02-19 to 2008-04-16; repeat barley assay: 2008-05-05 to 2008-05-26
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Study conducted according to the ISO 11269-2 protocol. No dose confirmation.
Qualifier:
according to
Guideline:
other: ISO 11269-2 protocol
Deviations:
not specified
GLP compliance:
no
Remarks:
Compliance statement to ISO 11269-2 protocol attached (see below)
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
Vehicle:
not specified
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.

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
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 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
Species:
Hordeum vulgare
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4 and RBM SO4
Basis for effect:
seedling emergence
Species:
Hordeum vulgare
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4 and RBM SO4
Basis for effect:
growth
Remarks:
shoot yield (dry)
Species:
Lactuca sativa
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4 and RBM SO4
Basis for effect:
seedling emergence
Species:
Lactuca sativa
Duration:
20 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4 and RBM SO4
Basis for effect:
growth
Remarks:
shoot yield (dry)
Reported statistics and error estimates:
The highest No Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC) were determined by ANOVA with a Duncan test.

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%).

Validity criteria fulfilled:
yes
Conclusions:
No effect was observed up to the largest dose tested of two upgraded ilmenite slags (UGI, Exxaro SO4 and RBM SO4) on two different endpoints (emergence and shoot yield) for both barley and lettuce, resulting in an unbounded NOEC of >= 10%.
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.

Description of key information

 Data are available for the effect of different upgraded ilmenite (UGI, >80% TiO2) slags on survival and reproduction of the terrestrial arthropod Folsomia candida. Conservatively, a long-term NOEC of 1000 mg/kg dw and a chronic LOEC of 3000 mg/kg dw is derived based on observed effects. In sum, TiO2 appears to have a low potential for toxicity to soil arthropods

Key value for chemical safety assessment

Additional information

Data are available for the effect of different upgraded ilmenite slags (UGI, >80% TiO2) on survival and reproduction of the terrestrial arthropod Folsomia candida. Conservatively, a long-term NOEC of 1000 mg/kg dw and a chronic LOEC of 3000 mg/kg dw is derived. Upgraded ilmenites (UGI) consist primarily (> 80%) of titanate, i.e., TiO2 with Fe, Al, Si, Mg and other metals, and are poorly soluble and not biodegradable. The transformation/dissolution of three UGI products at loadings of up to 100 mg/L over 24 h did not result in any significant release of titanium (Skeaff, 2007). Bulk and nano-TiO2 forms are also poorly soluble in environmental media (Brouwers, 2009; Klawonn, 2017 a-f). Based on similarity in composition and the same poor solubility of UGI and TiO2, read-across of ecotoxicological data from UGI to TiO2 is justified.

One supporting study on the acute toxicity of microsized TiO2 to Porcellio scaber is available and indicates that microsized TiO2 has a low toxic potential to terrestrial arthropods: Jemec et al. (2016) performed two non-standardized leaves-consumption tests, in which adult animals of both sexes of Porcellio scaber were offered two pieces of the same hazelnut leave either individually or in groups of 10 organisms for 14 d. Both pieces were either treated with deionized water (controls) or one piece was treated with deionized water and the other piece was treated with a suspension of micro-sized aluminium-zirconium coated TiO2 (1000 mg/kg dw leave). Consumption of control and treated leaves did not significantly differ (unbounded 14 d NOEC ≥ 1000 mg/kg dw leave, nominal), indicating that isopods neither avoided nor selected TiO2 treated leaves after 14 d of exposure to both treatments. Exposure occurred via food and not via the soil. Therefore, the results of this test are considered supporting data.

Furthermore, one supporting study on the acute toxicity of nanosized TiO2 to Porcellio scaber, is available. In this study, sonicated and non-sonicated dispersions of a nano-sized TiO2 material (15 nm, anatase) applied to dry leaves did not affect weight change, feeding rate, food assimilation efficiency, and survival of Porcellio scaber after 3 days of dietary exposure in a non-standardized test. Derived 3 d NOEC values were 3000 mg/kg diet dw. Furthermore, inconsistent dose-response relationships were observed for antioxidant enzyme activities at these effect levels. Exposure occurred via the food and not via the soil. Therefore, the results of this test are not considered for hazard assessment.

In sum, nano- and microsized TiO2 appears to have a low potential for toxicity to soil arthropods based on data available for springtails and isopods.