Studies suggest that people are more likely to buy and eat foods that are brighter or more vibrant in color. And titanium dioxide is one way to make that happen. You can find it in food products like candy, coffee creamer, baking and cake decorations, and white sauces.

A significant body of research, mostly from rodent models and in vitro studies, has linked titanium dioxide with health risks related to the gut, including intestinal inflammation, alterations to the gut microbiota, and more. It is classified by the International Agency for Research on Cancer (IARC) in Group 2B, as possibly carcinogenic to humans.

How pure TiO2 is extracted from titanium-containing molecules depends on the composition of the original mineral ores or feedstock. Two methods are used to manufacture pure TiO₂: a sulphate process and a chloride process.

Assessment of biocompatibility in prokaryotic cells

Different dermal cell types have been reported to differ in their sensitivity to nano-sized TiO₂ . Kiss et al. exposed human keratinocytes (HaCaT), human dermal fibroblast cells, sebaceous gland cells (SZ95) and primary human melanocytes to 9 nm-sized TiO₂ particles at concentrations from 0.15 to 15 μg/cm² for up to 4 days. The particles were detected in the cytoplasm and perinuclear region in fibroblasts and melanocytes, but not in kerati-nocytes or sebaceous cells. The uptake was associated with an increase in the intracellular Ca²⁺ concentration. A dose- and time-dependent decrease in cell proliferation was evident in all cell types, whereas in fibroblasts an increase in cell death via apoptosis has also been observed. Anatase TiO₂ in 20–100 nm-sized form has been shown to be cytotoxic in mouse L929 fibroblasts. The decrease in cell viability was associated with an increase in the production of ROS and the depletion of glutathione. The particles were internalized and detected within lysosomes. In human keratinocytes exposed for 24 h to non-illuminated, 7 nm-sized anatase TiO_2, a cluster analysis of the gene expression revealed that genes involved in the “inflammatory response” and “cell adhesion”, but not those involved in “oxidative stress” and “apoptosis”, were up-regulated. The results suggest that non-illuminated TiO₂ particles have no significant impact on ROS-associated oxidative damage, but affect the cell-matrix adhesion in keratinocytes in extracellular matrix remodelling. In human keratinocytes, Kocbek et al. investigated the adverse effects of 25 nm-sized anatase TiO₂ (5 and 10 μg/ml) after 3 months of exposure and found no changes in the cell growth and morphology, mitochondrial function and cell cycle distribution. The only change was a larger number of nanotubular intracellular connections in TiO₂-exposed cells compared to non-exposed cells. Although the authors proposed that this change may indicate a cellular transformation, the significance of this finding is not clear. On the other hand, Dunford et al. studied the genotoxicity of UV-irradiated TiO₂ extracted from sunscreen lotions, and reported severe damage to plasmid and nuclear DNA in human fibroblasts. Manitol (antioxidant) prevented DNA damage, implying that the genotoxicity was mediated by ROS.

With its storied history and distinct properties, lithopone remains a subject of historical significance and contemporary relevance. While its applications and popularity have evolved, its role in the annals of pigment history is indisputable.

Lithopone

Titanium dioxide is a naturally-occurring mineral found in the earth’s crust. Because of its white color, opaqueness, and ability to refract light, the ingredient is often used as a pigment, brightener, and opacifier, which is an ingredient that makes a formulation more opaque. Titanium dioxide is also a UV filter and so is an effective active ingredient in sunscreens. It’s often used in cosmetic loose and pressed powders, especially “mineral powder” cosmetics, in addition to other cosmetics, lotions, toothpaste, and soap.

Following a request for assessment in 2020 by the EU, the European Food Safety Authority (EFSA) assessed E171, particularly for its genotoxicity. In 2022, the agency deemed the food additive no longer safe for use.