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.

Prof. Matthew Wright, chair of EFSA’s working group on E171, noted: “Although the evidence for general toxic effects was not conclusive, on the basis of the new data and strengthened methods we could not rule out a concern for genotoxicity and consequently we could not establish a safe level for daily intake of the food additive.”

Titanium is a metal element found naturally in the environment. When it's exposed to oxygen in the air, it forms titanium oxides that are contained in many minerals, sands, soils, and dusts.

Exposure to titanium dioxide in utero and in breastfeeding children

Since then, there has been a few animal studies suggesting titanium dioxide is connected to cancer. A 2017 study in Scientific Reports, for instance, found that rats with titanium dioxide in their diet had impaired immune systems, which could contribute to autoimmune diseases and colorectal cancer.

The natural barite containing more than 95% of barium sulfate is mixed with anthracite in a ratio of 3:1 (mass), and is pulverized to a diameter of about 2 cm or less to enter a reduction furnace, and the front stage of the furnace temperature is controlled by 1000 to 1200 ° C, and the latter stage is 500 to 600 ° C, the reduction furnace rotates at a speed of 80s per revolution, the reaction conversion rate is 80% to 90%, the obtained barium sulfide enters the leaching device, the control temperature is above 65 ° C, and the content of barium sulfide is 701%, and then enters the clarification. The barrel is clarified and then added with zinc sulfate to control the zinc sulfate content to be greater than 28%, and the pH is 8-9, and a mixture of barium sulfate and zinc sulfide having a density of