Negligible respiratory irritation and inflammation potency of pigmentary TiO2 in mice.

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.