Abstract
This paper reviews studies on tissue distribution and toxicity after various routes of exposure to titanium dioxide（TiO2）, widely used in the production of paints, paper and plastics, as food additives and colorants, and increasingly, as nanpoparticles in pharmaceutical and cosmetics products, based on data published in openly available scientific literature. Titanium（Ti）was detected in the lung and medistinal lymph nodes, but not in the liver, kidney, spleen or basal brain with olfactory bulb, in rats that inhaled nano TiO2. Accumulation of TiO2 particles was observed in the brain, especially the olfactory bulb and hippocampus, after intranasal instillation of nano and fine TiO2 in mice. After dermal application of ultrafine and fine TiO2 in human volunteers, rabbits and pigs, deposition of Ti was observed in the stratum corneum and hair follicles, but not in the dermis. One report showed the accumulation of Ti in the spleen, heart, liver, lung and brain and histopathological changes in these tissues in mice that received dermal application of nano TiO2. However, there are serious concerns about this report due to the housing conditions of animals, which might have negatively impacted the experimental results. After oral administration of nano and fine TiO2 to mice, accumulation of Ti in the liver, kidney, spleen and kidney and histopathological changes in these organs and hippocampus were found. Although this review provides initial information on tissue distribution and toxicity after various routes of exposure to TiO2, further studies using characterized materials, relevant route of exposure, and dose closely reflecting actual levels of exposure are required.
