Titanium Dioxide

Abstract

Titanium is a naturally occurring element. The commercially most important titanium compound is pigmentary TiO 2 , whereas nano‐scaled TiO 2 represents only a small amount on the market. Since humans are exposed to TiO 2 at workplace or through consumer products, a thorough evaluation of its potential toxicity has been summarized herein. Dermal absorption of TiO 2 is deemed to be negligible, whereas oral and inhalation absorption has been reported but is assumed to be very low. TiO 2 has been shown to be of low acute oral, dermal, and inhalation toxicity and is considered to be void of skin and eye‐irritating properties. It also does not show any potential for skin and respiratory sensitization. Oral long‐term toxicity studies in rats report no adverse effects, and due to lack of dermal absorption of TiO 2 , it is assumed that dermal exposure is also not a hazard. TiO 2 does not show any primary mutagenicity and is also void of reproductive or developmental toxicity. However, in long‐term inhalation toxicity studies in rats, inflammation, fibroproliferative effects, and lung tumor formation has been observed but only under conditions of excessive particle lung overload. Carcinogenicity under such extreme conditions with complete cessation of lung clearance is considered to not imply a cancer hazard for humans, which is in line with epidemiological studies showing no causative link between TiO 2 particle exposure and cancer risk in humans. However, based on the available animal database, IARC in the past classified TiO 2 as possibly carcinogenic to humans, and the Risk Assessment Committee of ECHA also concluded that TiO 2 warrants a Category 2 classification for carcinogenicity.