Titanium oxide sulphate

Toxicity to soil microorganisms

Administrative data

Endpoint:

toxicity to soil microorganisms

Type of information:

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

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: One concentration tested. No exposure in soil. 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:

publication

Title:

Aquatic ecotoxicity tests of some nanomaterials

Author:

Velzeboer I, Hendriks AJ, Ragas AM, Van de Meent D

Year:

2008

Bibliographic source:

PMID: 19086210, Environmental Toxicology and Chemistry 27(9):1942-7

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Soil micro-organisms

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 (Sigma Aldrich, Zwijndrecht, The Netherlands), ordered as 10% (w/w) dispersion in water.

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 test surrogate titanium dioxidewhich is 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 other final hydrolysis product sulphuric acid should be included in the assessment according to the relevant test guidelines, even though sulphate is non-toxic and with regard to the rather high natural background concentrations irrelevant.
As sulphuric acid fully dissociates, the substance itself will not reach the 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.

Sampling and analysis

Analytical monitoring:

yes

Test substrate

Vehicle:

no

Test organisms

Test organisms (inoculum):

soil

Study design

Total exposure duration:

7 d

Test conditions

Details on test conditions:

Soil bacteria were sampled at Demmerik (The Netherlands) and added to 10M sterile Bis-tris(2-(bis(2-hydroxyethyl)amino)-2-(hydroxymethyl)propane-1,3-diol at pH 7. After 24h of incubation, the samples were transferred into multiwell, gram-positive plates.
These plates contained one organic substrate in each well together with a tetrazolium violet redox dye.
During one week, the color development was measured every day with a plate reader.

Nominal and measured concentrations:

100 mg TiO2/L nominal

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

7 d

Dose descriptor:

other: NOELR

Effect conc.:

>= 100 other: mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

respiration rate

Remarks:

detected colorimetrically using tetrazolium violet redox dye (Microtox® photometer )

Remarks on result:

other: Corresponds to 1.25 mmol/L

Effect concentrations 2

Duration:

7 d

Dose descriptor:

other: NOELR

Effect conc.:

>= 336 other: mg/l

Nominal / measured:

estimated

Conc. based on:

other: target compound titanium oxide sulphate

Basis for effect:

other: detected colorimetrically using tetrazolium violet redox dye (Microtox® photometer )

Remarks on result:

other: Converted from 1.25 mmol/L on the basis of MW TiOSO4 = 159.93 g/mol

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

The test article exhibited no subacute toxic effects to soil micro-organisms in saturated solution together with undissolved microdisperse matter in excess

Executive summary:

The subacute toxicity of nanoscaled titanium dioxide to soil micro-organisms was studied using bacteria sampled at Demmerik (The Netherlands). The limit test was conducted during 7 days. However no guideline protocol was followed, the experiment is well documented and meets generally accepted scientific standards. Thus the study is considered valid and conclusive.

The test organisms were exposed in aqueous solution to the test surrogate titanium dioxide, which is the substance formed by hydrolysis of target compound titanium oxide sulphate. 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 a nominal loading rate of 100 mg/L. The loading is far above the water solubility of the test article, which is about 1 µg/L. No analytical dose verification was performed. Due to the multiwell plate exposure no separation of the test organisms and the test article, e.g. by precipitation is suggested. The respiration of the test organisms was detected colorimetrically using tetrazolium violet redox dye.

In the sole loading the test article exhibited no effect and a NOELR of ≥ 100 mg/L was derived. Thus the applied loading is considered a NOELR with no corresponding LOELR. On the basis of the molar test article loading the level for the target chemical titanium oxide sulphate was assessed to be ≥ 336 mg/L. No threshold concentration can be derived.

In conclusion the test article exhibited no subacute toxic effects to soil micro-organisms in saturated solution together with undissolved microdisperse matter in excess.