Titanium dioxide is a mineral that’s used as a white coloring in a variety of products, including sunscreens, cosmetics, paints, and plastics. The pigment grade is also known as titanium white, pigment white 6, or CI 77891; it's the whitest and brightest of all known pigments.

According to a 2011 study published in Radiology and Oncology, titanium dioxide may lead to some adverse effects in the body, including oxidative stress, inflammation, and changes in cell signaling pathways. Additionally, pure titanium dioxide can be notably harmful when inhaled.

In 2017, French researchers from the Institut National de la Recherche Agronomique (INRAE) were among the first to examine the effects of E171 nanoparticles on the body. They fed rats a dose of 10mg of E171 per kilogram of body weight per day, which was similar to human exposure in food. The research, which was published in Scientific Reports, showed that E171 was able to traverse the intestinal barrier, pass into the bloodstream, and reach other areas of the body in rats. Researchers also found a link between immune system disorders and the absorption of titanium dioxide nanoparticles. 

TiO₂ NPs appeared to be more toxic to nematode Caenorhabditis elegans than submicron-sized TiO_2.  At a concentration of 1 mg/l, 7 nm particles affected its fertility and survival rate and were more toxic than 20 nm anatase particles. Similarly, Hu et al. showed that rutile particles (10–20 nm), at concentrations above 1 g/kg soil, can be bio-accumulated in earthworms, where they induce oxidative stress, inhibit the activity of cellulase and induce DNA and mitochondrial damage.