Titanium dioxide

Acute Toxicity: other routes

Administrative data

Endpoint:

acute toxicity: other routes

Remarks:

single intravenous injection

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

not specified

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

This study was not in accordance with any OECD acute toxicity guideline. The inital age of the animals and the body weight at the beginning of the study are not stated and the acclimatisation period to the laboratory conditions is not specified. The test substance is administered via intravenous injection, which is a non-physiological route of TiO2 administration. The injection volume was not specified and a concentration determination of the TiO2 NP suspension prior administration was not performed. Additionally, the body weights throughout the study were not recorded. No conclusion can be drawn from the above publication due to lack of quality, reliability and adequacy of the experimental data for the fulfilment of data requirements under REACH. The non-physiological route of administration via intravenous injection is not guideline conform and not suitable to assess acute toxicity. Furthermore, the test substance is not sufficiently characterised and limited number of parameters were investigated and the methodical setup is not adequately designed for risk assessment purposes of the test substance.

Data source

Reference

Reference Type:

publication

Title:

Acute Toxicity of Intravenously Administered Titanium Dioxide Nanoparticles in Mice

Author:

Xu, J. et al.

Year:

2013

Bibliographic source:

PLoS ONE 8(8):e70618

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

In this study mice were treated with a single intravenous injection of 4 different TiO2 NP concentrations in saline suspension. 14 days after TiO2 administration animal mortality, clinical signs, biochemical, hematological and histopathological effects and organ weights were analyzed.

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

Molecular formula:

O2Ti

IUPAC Name:

dioxotitanium

Test material form:

solid: nanoform

Details on test material:

- Particle size distribution: 42.30 ± 4.60 nm
- Crystal structure: Anatase (100%)
- Surface properties: Hydrophilia
- Impurities (identity and concentrations): Pb <2 ppm; Cd <1 ppm; As <1 ppm; Hg <1 ppm; Ni < 1ppm

Specific details on test material used for the study:

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: 10mg/mL stock suspension was sonicated for 30 seconds, kept on ice for 15 seconds and sonicated again on ice for 3 minutes.
- Final dilution of a dissolved solid: Before use, TiO2 NPs stock suspension was diluted to desired concentrations in fresh saline

Test animals

Species:

mouse

Strain:

ICR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Zhejiang Province Laboratory Animal Science Center
- Housing: Stainless steel cages

ENVIRONMENTAL CONDITIONS
- Temperature: 20 ± 2 °C
- Humidity: 60 ± 10 %
- Photoperiod: 12 hrs dark / 12 hrs light

Administration / exposure

Route of administration:

intravenous

Vehicle:

physiological saline

Details on exposure:

Single injection of TiO2 NPs saline suspension was administered through the tail vein (28 G needle)

Doses:

0, 140, 300, 645, 1387 mg/kg BW

No. of animals per sex per dose:

4 animals/sex/dose

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Necropsy of survivors performed: yes
- Other examinations performed: Behavior, mortality, clinical signs, body weight,organ weights, histopathology, blood biochemical analysis, hematology analysis

Statistics:

Results were expressed as mean ± standard deviation (SD). Multigroup comparisions of the mean were carried out by one-way analysis of variance (ANOVA) test. Dunnett´s test was used to compare the difference between the experimental groups and the control group. The statistical significance for all tests was set at P<0.05.

Results and discussion

Effect levels

Remarks on result:

other: see remarks

Remarks:

According to the author 2 males and 4 females in the highest treatment group died at study day 9. Organ weights of spleen increased, while organ weights of liver and kidney decreased in TiO2 NP treated animals. The levels of DBIL and IBIL in TiO2 NP treted mice decreased in a dose dependent manner and an increase in the WBC count in 645 mg/kg BW dose group could be observed. Histopathology revealed different degrees of damage in the brain, lung, spleen, liver and kidneys.

Mortality:

In the highest dose group (1387 mg/kg BW) 2 males and 4 females died at study day 9.

Clinical signs:

7 days after treatment, difference in eating and drinking patterns and physical activity were observed in the 1387 mg/kg dose group. They showed decreased food and water intake and decreased physical activity compared to control group animals.
The behavior of the mice in the other dose groups was normal throughout the study.

Body weight:

not specified

Gross pathology:

Organ weights:
Compared to control, coefficients of the spleens in TiO2 NPs treated mice increased significantly whereas coefficients of the liver and kidney decreased significantly. No significant effects were observed in the coefficients of the heart, lung or brain in TiO2 treated mice.

Other findings:

Blood biochemical analysis:
No significant differences were found in the serum levels of TBIL, ALT, AST, ALP, BUN, CREA, or CK in TiO2 NPs treated mice compared to the control group. The levels of DBIL and IBIL in TiO2 treated mice decreased in a dose dependent manner. The level of URCA in TiO2 NPs treated mice at 140 and 300 mg/kg BW were significantly increased compared to the control group.

Hematological analysis:
Intravenous injection of high doses of TiO2 NPs did not induce significant acute hematological toxicity except for an increase in the WBC count in 645 mg/kg BW dose group.

Histopathological detection:
The results show that TiO2 NPs treatment could induce different degrees of damage in the brain, lung, spleen, liver and kidneys. According to the author the liver tissue showed hepatocyte vacuolar degeneration, spotty necrosis of liver hepatocytes, along with inflammatory cell invasions in the bile ducts of the liver, and hydropic degeneration around the central vein. At higher doses, multifocal lesions were also observed in the liver. In the kidneys, swelling in the renal glomerulus in TiO2 NP treated mice was observed. In the spleen TiO2 NP treatment caused increased proliferation of local macrophages. The brain tissue showed neuronal cell degeneration and vacuoles were observed in the hippocampus. In the lung tissue, inflammatory cells, foamy cells and granulomatous lesions were observed. No pathological effects were observed in the heart of TiO2 NPs treated mice.

Applicant's summary and conclusion

Conclusions:

Xu et al. (2013) evaluated the acute toxicity of TiO2 after a single intravenous injection of TiO2 suspensions in male and female ICR mice (4M/4F per dose group) at 0, 140, 300, 645, and 1387 mg/kg bw. 14 days after injection behaviour, mortality, organ weights were recorded and blood biochemical and haematology analysis as well as histopathology examination was performed. Mortality of 2 males and 4 females in the highest treatment group was observed. Organ weights of spleen increased, while organ weights of liver and kidney decreased in TiO2 NP treated animals. Bilirubin levels decreased and WBC increased in a dose dependent manner. Histopathology revealed different degrees of damage in the brain, lung, spleen, liver and kidneys. The test material is insufficiently characterised. Due to an absence of a clear designation, purity or impurity information, it remains unclear whether the test item was in fact of industrial origin and therefore of relevance for the hazard and risk assessment of titanium dioxide. This study is not in accordance with any OECD acute toxicity guideline. The initial age of the animals and the body weight at the beginning of the study are not stated and. The test substance is administered via intravenous injection is a non-physiological route of TiO2 administration. The injection volume was not specified and a concentration determination of the TiO2 NP suspension prior administration was not performed. Additionally, the body weights throughout the study were not recorded. Based on the above listed shortcomings, the study was considered not reliable and was therefore disregarded.