Dichloride titanium oxide

Toxicity to soil macroorganisms except arthropods

Administrative data

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

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

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Data from conference poster, full study not available

Data source

Reference

Reference Type:

other: conference poster

Title:

Toxicity of seven different nanoparticles to Eisenia fetida.

Author:

Heckman et al

Year:

2008

Bibliographic source:

SETAC 25-29 May, 2008, Warsaw, Poland

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Titanium dioxide

EC Number:

236-675-5

EC Name:

Titanium dioxide

Cas Number:

13463-67-7

IUPAC Name:

dioxotitanium

Constituent 2

Reference substance name:

Rutile (TiO2)

EC Number:

215-282-2

EC Name:

Rutile (TiO2)

Cas Number:

1317-80-2

IUPAC Name:

dioxotitanium

Details on test material:

- 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

* TiO2 nanoparticles (from Evonik Degussa), nominal particle size 21 nm, surface area 50 m²/g.
* bulk TiO2

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 titanium dioxide and thus with exactly the substance formed by hydrolysis of the target chemical.
OECD TGD 222 (2004) recommends “The soil pH should not be adjusted when acidic or basic substances are tested“. Therefore the additionally released hydrogen chloride should be included in the assessment according to the relevant test guidelines, even though chloride is non-toxic and with regard to the rather high natural background concentrations irrelevant.
As hydrogen chloride fully dissociates, the substance itself will not reach the sediment/terrestrial environment except via direct exposure, which is not expected in quantities exceeding the soil buffering capacity. In conclusion the test was conducted with the relevant transformation product.
Recalculation of the measured threshold values is required on an isomolar basis as the analogue material results from isomolar transformation of the target chemical.

Test organisms

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Study design

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

yes

Total exposure duration:

4 wk

Post exposure observation period:

hatching of produced cocoons was monitored during the following 4 weeks

Test conditions

Details on test conditions:

4 replicates

Nominal and measured concentrations:

nominal: 1000 mg/kg dry soil

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

4 wk

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

bulk TiO2

Basis for effect:

other: cocoon production

Effect concentrations 2

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

bulk TiO2

Basis for effect:

other: hatchability and juvenile production

Effect concentrations 3

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

>= 2 137 mg/kg soil dw

Nominal / measured:

estimated

Conc. based on:

other: parent chemical titanium tetrachloride

Basis for effect:

other: hatchability and juvenile production

Remarks on result:

other: Converted from 12.5 mmol TiO2 corresponding to 1000 mg (MW TiO2 = 79.899 g/mol, MW TiCl4 = 189.712 g/mol)

Effect concentrations 4

Duration:

8 wk

Dose descriptor:

NOEC

Effect conc.:

>= 1 519 mg/kg soil dw

Nominal / measured:

estimated

Conc. based on:

other: target compound titanium oxychloride

Basis for effect:

other: hatchability and juvenile production

Remarks on result:

other: Converted from 12.5 mmol TiO2 corresponding to 1000 mg (MW TiO2 = 79.899 g/mol, MW TiOCl2 = 134.77 g/mol)

Details on results:

data derived from graph
The nanoparticles tested in parallel showed no effects on the 4 wk cocoon production (± 20% effect variability)), but 8 wk hatchability and juvenile production were hampered (± 25 and 50% effect variability)

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

The study indicates no chronic toxic effects to soil macroorganisms exposed to microdisperse matter, while nanoscaled material could exhibit effects.

Executive summary:

The chronic toxicity of titanium dioxide to earthworm (Eisenia fetida) reproduction was studied in a limit test according to the OECD TGD 222 protocol. In the present study the soil was spiked with the analogue material titanium dioxide and thus with exactly the substance formed by hydrolysis of the target chemical titanium oxychloride. Recalculation of the measured value was made on an isomolar basis as the analogue material results from isomolar transformation of the target chemical.

The insoluble test item was applied in one concentration of nominal 1000 mg/kg soil dw. The loading is far above the water solubility of the test article, which is about 1 µg/L. No analytical dose verification was performed. The test organisms were during 8 weeks exposed to bulk or nanoscaled test article. Cocoon production was assessed after 4 weeks and hatchability and juvenile production after 8 weeks.

The bulk material exhibited no effects. While the nanoparticles tested in parallel showed no effects on the 4 wk cocoon production (± 20% effect variability, as data derived from graph), the 8 wk hatchability and juvenile production were hampered (± 25 and 50% effect variability.

In the highest concentration corresponds to 2137 mg/kg soil dw of the parent chemical titanium tetrachloride, or to 1519 mg/kg soil dw of the target compound titanium oxychloride, resp. As it is assessed that the titanium dioxide formed by hydrolysis is unlikely to reach the soil in nanoscaled crystalline particle form, it is concluded that no hazard exists with regard to the target chemical. Thus no threshold concentration for titanium tetrachloride or titanium oxychloride can be derived. Nonetheless the study could indicate that crystalline nanoparticles may have and impact of the reproduction of soil macroorganisms such as earthworms.

In conclusion the study indicates no chronic toxic effects to soil macroorganisms exposed to microdisperse matter, while nanoscaled material could exhibit effects.