Dichloride titanium oxide

Toxicity to terrestrial arthropods

Administrative data

Endpoint:

toxicity to terrestrial arthropods: short-term

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: No guideline study, but meeting generally accepted scientific standards; Exposure via food (TiO2 sprayed on hazelnut leaves) and not via soil; Conclusive

Data source

Reference

Reference Type:

publication

Title:

Effects of ingested nano-sized titanium dioxide on terrestrial isopods (Porcellio scaber).

Author:

Jemec A, Drobne D, Remskar M, Sepcić K, Tisler T

Year:

2008

Bibliographic source:

PMID: 19086208, Environmental Toxicology and Chemistry 27(9):1904-14

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Study on the effect of TiO2 exposure via food on terrestrial isopods

GLP compliance:

no

Application method:

oral

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

TiO nanoparticles, supplied by Sigma-Aldrich
Purity 99.7%
Anatase crystalline
nominal average particle size: 15 nm
Surface area: 190-290 m²/g
TiO2 suspended in bidistilled water with pH 5.7
sonicated suspension: median measured particle size: 350 to 500 nm
non-sonicated suspension: median measured particle size: 780 to 970 nm

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 diet of the test organisms was spiked with the analogue material titanium dioxide and thus with exactly the substance formed by hydrolysis of the target chemical. In case terrestrial arthropods may get in contact with a pollutant by ingestion, the buffering capacity of the soil would probably neutralise acidity related effects cased by the hydrogen chloride, which is released in tetra molar quantities during hydrolysis of the titanium tetrachloride. Relevant guidance documents as e.g. ISO 11267:1999 include therefore pH adjustment. 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. Chloride is non-toxic and with regard to the rather high natural background concentrations irrelevant. Thus additionally released hydrogen chloride should be disregarded.
In conclusion the test was conducted with the relevant transformation product.

Sampling and analysis

Analytical monitoring:

no

Test substrate

Vehicle:

not specified

Test organisms

Test organisms (species):

Porcellus scaber

Animal group:

Crustacea (soil-dwelling woodlouse)

Details on test organisms:

- Common name: Common rough woodlouse or simply rough woodlouse

Animals were brought to the laboratory from three different field locations in Slovenia: two sites near Domzale and one site at Radlek.
They were collected under the litter layer of an uncontaminated location.
In the laboratory, they were kept in a terrarium filled with 2-5 cm layer of moistened sand and soil and a thick layer of partly decomposed hazelnut tree leaves (Corylus avellana).
Adults with body weights ranging from 30 to 80 mg and of both sexes and all molt stages were exposed to TiO2 within 1 to 11 days after collection in the field.

Study design

Study type:

laboratory study

Limit test:

no

Total exposure duration:

3 d

Test conditions

Test temperature:

21±1 °C

Humidity:

Relative humidity: close to 100%
Humidity was maintained by regular spraying with tap water on the internal side of the lids.

Photoperiod and lighting:

16:8h light:dark photoperiod (15 lux: 5 lux) without direct proximity of the lamp

Details on test conditions:

Each animal was placed individually in a Petri dish, to which individual pieces of dry leaves dosed with TiO2 were added.
2 or 3 replicates per concentration
6 to 10 animals per replicate

Nominal and measured concentrations:

Nominal: 0, 0.1, 0.5, 1, 10, 100, 1000, 2000 and 3000mg/kg leaf

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 3 000 mg/kg diet

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Corresponds to 37.5 mmol/kg diet; no difference between nonsonicated and sonicated TiO2

Effect concentrations 2

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 3 000 mg/kg diet

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: weight change

Remarks on result:

other: Corresponds to 37.5 mmol/kg diet; no difference between nonsonicated and sonicated TiO2

Effect concentrations 3

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 3 000 mg/kg diet

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: feeding rate and defecation rate

Remarks on result:

other: Corresponds to 37.5 mmol/kg diet; no difference between nonsonicated and sonicated TiO2

Effect concentrations 4

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 3 000 mg/kg diet

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: food assimilation efficiency

Remarks on result:

other: Corresponds to 37.5 mmol/kg diet; no difference between nonsonicated and sonicated TiO2

Effect concentrations 5

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 7 114 mg/kg diet

Nominal / measured:

estimated

Conc. based on:

other: parent chemical titanium tetrachloride

Basis for effect:

other: mortality, weight change, feeding rate and defecation rate, food assimilation efficiency

Remarks on result:

other: Converted from 37.5 mmol/kg diet on the basis of MW TiCl4 = 189.712 g/mol

Effect concentrations 6

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

>= 5 055 mg/kg soil dw

Nominal / measured:

estimated

Conc. based on:

other: target compound titanium oxychloride

Basis for effect:

other: mortality, weight change, feeding rate and defecation rate, food assimilation efficiency

Remarks on result:

other: Converted from 37.5 mmol/kg diet on the basis of MW TiOCl2 = 134.77 g/mol

Details on results:

Results on enzyme activity (considered less relevant endpoint on a population level):

Endpoint / Effect conc. / Conc. based on Basis for effect / Remarks (e.g. 95% CL)
NOEC / 1000 mg/kg diet test mat. TiO2 / Enzyme activity (catalase and glutathione-S-transferase) / Non-sonicated
LOEC / 2000 mg/kg diet test mat. TiO2 / Enzyme activity (catalase and glutathione-S-transferase) / Non-sonicated
NOEC / >= 3000 mg/kg diet test mat. TiO2 / Enzyme activity (catalase and glutathione-S-transferase) / Sonicated

Reported statistics and error estimates:

significant differences determined by Kruskal-Wallis analysis and Mann-Whitney U test

Applicant's summary and conclusion

Validity criteria fulfilled:

not applicable

Conclusions:

The test article exhibited no acute toxic effects to terrestrial arthropods fed with nanodisperse matter.

Executive summary:

The acute toxicity of titanium dioxide to terrestrial arthropods was studied using the common rough woodlouse, an isopod (Porcellio scaber). The limit test was conducted during 3 days and however no GLP standards or a 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 animals were fed with the analogue material titanium dioxide and thus with exactly the substance formed by hydrolysis of parent compound titanium tetrachloride via 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 a concentration of 3000 mg/kg diet. The endpoints mortality, weight change, feeding rate and defecation rate, and food assimilation efficiency were investigated. In addition results from measurements of enzyme activity were given.

In the sole concentration the test article exhibited no significant effects on the macroscopic parameters, but altered enzyme activity. The latter effects were regarded as a less relevant endpoint on a population level and thus disregarded for hazard assessment. Accordingly a NOEC of > 3000 mg/kg diet with no corresponding LOEC was derived. No threshold concentration can be derived. On the basis of the molar test article concentration the level for the parent chemical, titanium tetrachloride, was assessed to be ≥ 7114 mg/kg diet.

On the basis of the molar test article concentration the level for the target chemical, titanium oxychloride, was assessed to be ≥ 5055 mg/kg diet.

In conclusion the test article exhibited no acute toxic effects to terrestrial arthropods fed with nanodisperse matter.