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Ecotoxicological information

Toxicity to terrestrial arthropods

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Reference
Endpoint:
toxicity to terrestrial arthropods: long-term
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
May 2008
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: ISO 11267 (1999) guideline study, no quantification of titanium concentration of test soils
Qualifier:
according to
Guideline:
ISO 11267 (Inhibition of Reproduction of Collembola by Soil Pollutants)
Deviations:
not specified
GLP compliance:
no
Remarks:
Compliance statement to ISO 11267 guideline attached (see below)
Application method:
not specified
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
Folsomia candida
Animal group:
Collembola (soil-dwelling springtail)
Study type:
laboratory study
Limit test:
no
Total exposure duration:
28 d
Test temperature:
not reported, however test performed according to ISO 11267 (1999) guideline: climatic chamber with a controlled temperature of 20°C to 22°C
pH (if soil or dung study):
pH after spiking of the soil:
preliminary test pH range: 6.91- 7.22
Definitive test pH range Exxaro SO4: 5.28-6.51
Definitive test pH range RBM SO4: 5.64-6.36
Repeated definitive test with Exxaro SO4: 5.78-6.63
Humidity:
no data
Photoperiod and lighting:
no data
Details on test conditions:
TEST SYSTEM
- Test container (material, size): Glass container of about 80 mL capacity and with a diameter of about 5 cm
- Amount of soil or substrate: no data
- No. of organisms per container (treatment): 4
- No. of replicates per treatment group: 4
- No. of replicates per control: 4


SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Soil substrate as described in the ISO 11267 guideline was used
- Soil texture (if natural soil)
- % sand: 70
- % peat: 10
- % clay: 20


- Soil taxonomic classification: no data
- Soil classification system: no data
- Composition (if artificial substrate):
Sphagnum peat, air-dried, finely ground and with no visible plant remains; kaolinite clay (air-dry) containing not less than 30% kaolinite; industrial quartz sand (air dried, and predominantly fine sand with more than 50% of particle size 0,05 mm to 0,2 mm)
- Organic carbon (%): no data
- Maximum water holding capacity (in % dry weigth): no data
- CEC: no data
- Pretreatment of soil: no data
- Storage (condition, duration): no data
- Stability and homogeneity of test material in the medium: no data


OTHER TEST CONDITIONS
- Photoperiod: Controlled light:dark cycle between 12h:12h and 16h: 8h L:D
- Light intensity: 400 lx to 800 lx


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : survival and reproduction


VEHICLE CONTROL PERFORMED: no data


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3 to 3.3
- Justification for using less concentrations than requested by guideline: not applicable
- Range finding study
- Test concentrations: A preliminary chronic soil testing was initiated using maximum concentration of 10% (weight by weight)
- Results used to determine the conditions for the definitive study: Based on the preliminary results, UGI products with the lowest and highest effects (Exxaro SO4 and RBM SO4, respectively) were selected to perform further definitive testing covering the range of the observed effects
Nominal and measured concentrations:
Nominal test concentrations:
Preliminary test: control, maximum concentration of 10% (weight by weight)
Definitive test: control; 0.1; 0.3; 1; 3; and 10% of Exxaro SO4 and RBM SO4
Repeated definitve test: control, 0.03; 0.1; 0.3; 1; 3 and 10% of Exxaro SO4
Reference substance (positive control):
not specified
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
0.1 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4
Basis for effect:
other: survival
Duration:
28 d
Dose descriptor:
LOEC
Effect conc.:
0.3 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4
Basis for effect:
other: survival
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
0.1 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4
Basis for effect:
reproduction
Duration:
28 d
Dose descriptor:
LOEC
Effect conc.:
0.3 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
Exxaro SO4
Basis for effect:
reproduction
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
RBM SO4
Basis for effect:
mortality
Duration:
28 d
Dose descriptor:
NOEC
Effect conc.:
>= 10 other: %
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
RBM SO4
Basis for effect:
reproduction
Reported statistics and error estimates:
Preliminary test: the p-values were calculated with the t-test: two-sample, assuming equal variances (two sided confidence interval)
The p-values of the definitive and repeated definitive test were calculated with the Dunnet test.

Preliminary test:

Overview number of surviving adults and number of juveniles of Folsomia candida after 28 days. Reduction of survival and reduction of reproduction are reported between brackets (in %) - preliminary test:

   # surviving adults (%) # juveniles (%) 
 Control  8.25  223
Tinfos SO4  4.75 (42%)  107 * (52%)
 Exxaro SO4  4.50 * (45%)  140 (37%)
 QIT Sorelslag  3.25 ** (61%)  118 ** (47%)
RBM Cl  2.75 *** (67%)  127 ** (43%)
 Exxaro Cl  2.25 *** (73%)  104 ** (54%)
 QIT UGS  2.00 *** (76%)  64 *** (71%)
 RBM SO4  0.75 *** (91%)  11 *** (95%)
 Namakwa SO4  0.75 *** (91%)  12 *** (95%)
 Namakwa Cl  0.25 *** (97%)  13 *** (94%)

*: significant difference (p ≤ 0.05); ** (p ≤ 0.01); *** (p ≤ 0.001)

Definitive test:

Overview 28d chronic Folsomia candida test at 5 different concentrations with RBM SO4 and Exxaro SO4. Reduction of survival and reduction of reproduction are reported between brackets (in %) - definitive test:

   # surviving adults (%)  # juveniles (%)
 Control  8.00  125
RBM SO4 0.1% 7.75 (3%)  99 (21%)
 RBM SO4 0.3% 6.75 (15%)  100 (20%)
 RBM SO4 1%  3.50 (56%)  84 (33%)
 RBM SO4 3%  6.75 (15%)  110 (12%)
 RBM SO4 10%  5.25 (34%)  138 (-10%)
 Exxaro SO4 0.1%  7.75 (3%)  108 (13%)
 Exxaro SO4 0.3%  1.00 *** (87%)  39 *** (68%)
 Exxaro SO4 1%  0.00 *** (100%)  31 *** (75%)
 Exxaro SO4 3%  0.25 *** (96%)  13 *** (89%)
 Exxaro SO4 10%  0.75 *** (90%)  27 *** (78%)

***: p < or = 0.001

A significant reduction of survival (87-100%) and reproduction (68 -89%) was observed for the 4 highest test concentrations with Exxaro SO4. The NOEC and LOEC are respectively 0.1% and 0.3%. The effects observed in the highest test concentration (10%) were more outspoken than in the preliminary test. The lower pH of the soil in comparison with the pH of the soil used in the preliminary test is probably not the cause of the higher toxicity. RBM SO4 exhibits for example lower effects (34% on survival in the highest test concentration, i.e. 10% w/w and even no effect at all for the endpoint reproduction). Due to the high variability the observed effects with RBM SO4 for the endpoint survival were not deemed significant. Hence, the unbounded NOEC is > or = 10%. A plausible explanation, as was also the case for the aquatic tests is the heterogeneous nature of the tested UGI products.

Repeated definitive test:

In order to have a better idea with regard to the robustness of the obtained test results the test was repeated with Exxaro SO4.

Overview repeated 28d chronic Folsomia candida test at 6 different concentrations with Exxaro SO4. % reduction of survival and recution of reproduction are reported between brackets - repeated definitive test:

 UGI # surviving adults (%)  # juveniles (%) 
 Control  9.75  348.75
 Exxaro SO4 0.03%  8 (17.95%)  151 *** (56.70%)
 Exxaro SO4 0.1%  8.25 (15.38%)  252.25 (27.67%)
 Exxaro SO4 0.3%  7 ** (28.21%)  152.75 *** (56.20%)
 Exxaro SO4 1%  9.25 (5.13%)  296.5 (14.98%)
 Exxaro SO4 3%  7.25 ** (25.64%)  261.5 (25.02%)
 Exxaro SO4 10%  8 (17.95%)  244 (30.04%)

*: significant difference (p < or = 0.05); ** (p < or = 0.01); *** (p < or = 0.001)

The results of the repeated test with Exxaro SO4 do not confirm the high toxicity found in the first definitive test. No clear dose-response curve can be derived from the results of this repeated definitive chronic test. Fungi formation occurred on cultures with 0.03% and 0.3% Exxaro SO4. However, this does not seem to have influenced the results. The variability in test responses can only be related to the heterogeneity of the UGI products.

Validity criteria fulfilled:
yes
Conclusions:
No firm conclusion on the toxicity of different upgraded ilmenites (UGI) slags to Folsomia candida can be drawn due to the heterogeneous nature of the UGI products. As a worst case approach the results of the first definitive terrestrial ecotoxicity test with springtail Folsomia candida for the UGI Exxaro SO4 can be used. This test yielded a NOEC of 0.1% and a LOEC of 0.3%.
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.