Negligible respiratory irritation and inflammation potency of pigmentary TiO₂ in mice

Abstract

Titanium dioxide (TiO₂) is manufactured in millions of tons yearly, and it is used widely as pigment in various applications. Until recently, TiO₂ was considered toxicologically harmless and without adverse health effects. In this study, respiratory irritation and inflammation potencies of commercially available pigmentary TiO₂ particles (<5 µm, rutile) were studied. Single head-only exposures (30 min) of male Crl:OF1 mice at mass concentrations 6, 11, 21, and 37 mg/m³, and repeated exposures (altogether 16 h, 1 h/day, 4 days/week for 4 weeks) of female BALB/c/Sca mice at mass concentration of 16 mg/m³ to pigmentary TiO₂ were conducted. Minor sensory irritation was observed during acute and repeated exposures seen as elongation of the break after the inhalation, which is typical in sensory irritation, and caused by closure of the glottis inhibiting airflow from the lungs after inspiration. No pulmonary irritation, airflow limitation, nasal or pulmonary inflammation was observed. In conclusion, the respiratory irritation and inflammation potencies of the studied pigmentary TiO₂ particles seemed to be low and thus can serve as an ideal control exposure agent in short-term studies in mice.

• Airway irritation
• inflammation
• inhalation
• titanium dioxide

Acknowledgements

The authors acknowledge the personnel of the National Laboratory Animal Centre, especially senior laboratory technician Auli Nissinen, for technical help.

Declaration of interest

The study was financed by the Academy of Finland, FinNano program (grant 117924), Graduate School in Environmental Health (SYTYKE), and Finnish Cultural Foundation, North Savo Regional fund.

Supplementary material available online

Supplementary Figure S1.