Titanium dioxide

Immunotoxicity

Description of key information

No conclusion can be drawn from the publications due to lack of quality, reliability and adequacy of the experimental data for the fulfilment of data requirements under REACH.

 

The references contained in this section represent in vitro and in vivo experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. All references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH and hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.

Key value for chemical safety assessment

Effect on immunotoxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

immunotoxicity, other

Remarks:

in vitro, cell culture

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

other: not rated according to Klimisch et al.

Rationale for reliability incl. deficiencies:

other:

Remarks:

The references contained in this summary entry represents in vitro experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. The references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH andhazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.

Principles of method if other than guideline:

Liu, R. et al. (2010):
Test substance: TiO2 microsized particles (obtained from Shanghai Titanium dioxide Materials Technology Company Ltd. (China) (crystalline phase anatase, primary particle size 200 nm, particle size in culture medium 287 nm, specific surface area 4 m²/g)
and three different TiO2 nanoparticles, thereof NP-1, NP-2 and NP-3:
- NP-1 from Hongsheng Materials Technology Company Ltd. (China) (crystalline phase anatase, primary particle size 5 nm, particle size in culture medium 348 nm, specific surface area 210 m²/g)
- NP-2 obtained from Degussa (crystalline phase 80 % anatase 20 % rutile, primary particle size 21 nm, particle size in culture medium 238 nm, specific surface area 50 m²/g)
- NP-3 from Hongsheng Materials Technology Company Ltd. (China) (crystalline phase rutile, primary particle size 50 nm, particle size in culture medium 212 nm, specific surface area 30 m²/g)
Test system: pulmonary alveolar macrophages (PAM) isolated from lung lavage fluid of Sprague-Dawley rats
Doses/consentrations: 300, 150, 75, 37.5, 18.75 µg/mL
Exposure conditions: single exposure for 24 h
Negative control: untreated cells
Positive control: not specified
Parameters investigated: nitric oxide (No) and cytokine assay (incl. TNF-alpha, IL-6), phagocytosis ability (uptake of neutral red dye), chemotactic ability (Transwell chamber migration assay), Fc receptor expression (rosettes formation assay), MHC class II expression (flow cytometry)

Remarks on result:

other:

Remarks:

Liu, R. et al. (2010): The study aims to identify correlations of the crystal structure, surface area and doses with immunologic alterations. Quantity of TiO2 particles inside PAMs increased dose-dependant, PAMs displayed incomplete membranes after exposure to NP-1 and NP-2. The NO level significantly increased after exposure to >18.5 µg/mL of NP-1 and NP-2 and to > 37.5 µg/mL of NP-3 and microsized TiO2. TNF-alpha levels were significantly increased after exposure to 18.5 µg/mL NP-1, but only slightly increased after exposure to 300 µg/mL NP-2, NP-3 and microsized TiO2. IL-6 levels were significantly increased after exposure to > 75 µg/mL NP-1 and > 18.75 µg/mL NP-2, as well as 300 µg/mL NP-3 and microsized TiO2. Phagocytic ability and chemotactic was significantly decreased at all doses and test substances. Decreased rosettes formation with sensitised erythrocytes was observed after exposure to TiO2, indicating a decreased Fc receptor expression. Flow cytometry indicated decreased expression of MHC class II molecules after exposure to TiO2.

Conclusions:

No conclusion can be drawn from the above publications due to lack of quality, reliability and adequacy of the experimental data for the fulfilment of data requirements under REACH.

The references contained in this summary entry represent in vitro experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. All references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH and hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.

Liu, R. et al. (2010):
The identity of the isolated cells from rat lung lavage fluid was not analysed, the protocol merely describes the culture of adherent cells. Regarding the in vitro assays, results are questionable since there are experimental / methodical deficiencies (e.g. no data of calibration of the test system, no positive controls and insufficient documentation of data (raw data, tables)). Furthermore, an analytical verification of target concentration is missing. Number of replicates in some assays is not elusive from documentation. The results of the fluorescence activated cell sorting cannot be verified as reliable since there is a lack of data (e.g. frequency of measurements, gating, clusting / choice and differentiation between dead or alive cell populations, no positive control).

Reference 2

Endpoint:

immunotoxicity: inhalation

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Reliability:

other: not rated according to Klimisch et al.

Rationale for reliability incl. deficiencies:

other:

Remarks:

The references contained in this summary entry represents in vivo experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. The references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH andhazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.

Principles of method if other than guideline:

Husain, M. et al. (2015):
Test substance: Titanium dioxide nanoparticles (UV-Titan L181, Kemira, Pori, Finland), surface modified with zirconium, silicon, aluminium, and polyalcohol, primary particle size 20.6 nm, surface area 107.7 m²/g, 70.8 % rutile
Dose/concentration: Exp1: 18 and 162 µg, Exp2: 162 µg
Control(s): vehicle control (0.9 % NaCl MilliQ water containing 10 % v/v acellular BAL collected from C57BL/6 mice)
No. of animals per sex per dose: Exp1: 6, Exp2: 3
Duration of treatment / exposure: not applicable
Frequency of treatment: single application
Post exposure period: Exp1: 24 hours and 28 days, Exp2: 4 hours and 24 hours
Parameters investigated:
Exp1: TiO2 content in liver and heart tissues (via hyperspectral microscopy), profile of cardiovascular and hepatic global genomic responses after TiO2 translocation
Exp2: TiO2 content in blood

Species:

other: Husain, M. et al. (2015): mouse (C57BL/6)

Sex:

female

Route of administration:

other: Husain, M. et al. (2015): intratracheal instillation

Remarks on result:

other:

Remarks:

Husain, M. et al. (2015): Exp1: Notable amounts of TiO2 were found in livers of mice exposed to the 18 and 162 µg doses sampled 24h post-exposure, decreased amount was observed at 28d post-exposure. Trace amounts of TiO2 were detected at both doses and time points. Activation of complement cascade and inflammatory processes in heart and specific activation of complement factor 3 in blood, suggesting activation of an early innate immune response essential for particle opsonisation and clearance, was observed. The liver showed a subtle response with changes in the expression of genes associated with acute phase response. Exp2: Trace amounts of TiO2 were detected at the 24h post-exposure

Conclusions:

No conclusion can be drawn from the above publications due to lack of quality, reliability and adequacy of the experimental data for the fulfilment of data requirements under REACH.

The references contained in this summary entry represent in vivo experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. All references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH and hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.

Husain, M. et al. (2015):
Regarding the hyperspectral microscopy results, results are questionable since there are experimental / methodical deficiencies (e.g. no data of calibration or validation of the test system, no confirmation of location within cells vie z-axis analysis, no positive controls and an insufficient characterisation of test material). The health status of the animals was not documented. Furthermore, only 2 doses were tested and the vehicle used is unsuitable for risk assessment, since the identity and characteristics are not documented sufficiently.

Endpoint conclusion

Endpoint conclusion:

no study available

Effect on immunotoxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Effect on immunotoxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Immunotoxicity

Summary entry – Immunotoxicity

During a literature search, two references were identified representing in vivo immunotoxicity investigations in mice and rats, which received either pigment-grade or nano-form titanium dioxide. The route of administration was either via intratracheal instillation or oral (gavage). Furthermore, one reference was identified, representing an in vitro immunotoxicity investigation in pulmonary alveolar macrophages isolated from rats. The study designs of the in vivo and in vitro studies are not in accordance with accepted guidelines and are therefore of limited relevance for chemicals hazard assessment. Further, the references usually lack significance due to, e.g., poor test item characterisation, missing dose response relationship, missing analytical verification of target concentrations and/or missing information on cell identity. It is therefore concluded that all references do not fulfil the criteria for quality, reliability and adequacy of experimental data under REACH for hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The studies given below were therefore included in the IUCLID for information purposes only:

 

Liu, R. et al. (2010): the identity of the isolated cells from rat lung lavage fluid was not analysed, the protocol merely describes the culture of adherent cells. Regarding the in vitro assays, results are questionable since there are experimental / methodical deficiencies (e.g. no data of calibration of the test system, no positive controls and insufficient documentation of data (raw data, tables)). Furthermore, an analytical verification of target concentration is missing. Number of replicates in some assays is not elusive from documentation. The results of the fluorescence activated cell sorting cannot be verified as reliable since there is a lack of data (e.g. frequency of measurements, gating, clustering / choice and differentiation between dead or alive cell populations, no positive control). 

 

Husain, M. et al. (2015): regarding the hyperspectral microscopy results, results are questionable since there are experimental / methodical deficiencies (e.g. no data of calibration or validation of the test system, no confirmation of location within cells vie z-axis analysis, no positive controls and an insufficient characterisation of test material). The health status of the animals was not documented. Furthermore, only 2 doses were tested and the vehicle used is unsuitable for risk assessment, since the identity and characteristics are not documented sufficiently.

 

Hashem, M.M. et al. (2020): The publication is not relevant for human health risk assessment since the test item data on particle characterisation is poorly described. Food grade titanium dioxide was obtained from Sigma. However, no further information was provided. Since the production process and impurities of the administered test substance is not known, the influence of the other simultaneously administered process chemicals is unclear, which raises doubts as to whether the effects can really be attributed to titanium dioxide E171. The experimental design is insufficiently documented and not in accordance with any relevant guideline. The concentration of the applied dose formulations was not analysed and only male rats were used. Further, according to the stated body weights, the animals were 4-5 weeks old and thus not assumed to be mature rats. It is also questionable to use such young rats in an investigation of the immune system since the immune system is not fully developed. Additionally, only two dose groups were tested which does not allow a dose-response related analysis. Moreover, individual data are not presented. Due to all these limitations, this study is considered not reliable.

 

Conclusion

There is currently no relevant and reliable guideline compliant study available for the endpoint immunotoxicity. During comprehensive literature search, three references were identified, which reported in vivo and in vitro studies investigating the potential of immunotoxicity of pigment-grade or nano-form titanium dioxide. The study designs of these studies are not in accordance with accepted guidelines and are therefore of limited relevance for chemicals hazard assessment. Further, the references usually lack significance due to, e.g., poor test item characterisation, missing dose response relationship, missing analytical verification of target concentrations and/or missing information on cell identity. It is therefore concluded that all references do not fulfil the criteria for quality, reliability and adequacy of experimental data under REACH for hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The studies were therefore included for information purposes only.

Justification for classification or non-classification

No conclusion can be drawn from the publications due to lack of quality, reliability and adequacy of the experimental data for the fulfilment of data requirements under REACH.

 

The references contained in this section represent in vitro and in vivo experiments with investigations on immunotoxicity with very limited value for risk assessment purposes. All references do not fulfil the criteria for quality, reliability and adequacy of experimental data for the fulfilment of data requirements under REACH and hazard assessment purposes (ECHA guidance R4 in conjunction with regulation (EC) 1907/2006, Annexes VII-X). The information contained therein were included for information purposes only.