Why does the exposure route matter, and what's the risk? 

Yet another study, this one published in 2006 by the International Agency for Research on Cancer said there was insufficient evidence to conclude that titanium dioxide causes cancer. However, the study also categorized the ingredient as a potential human carcinogen.

In a 2017 study published in Scientific Reports, researchers exposed rats to human-relevant levels of E171 to examine the effects of intestinal inflammation and carcinogenesis. They saw that “a 100-day E171 treatment promoted colon microinflammation and initiated preneoplastic lesions while also fostering the growth of aberrant crypt foci in a chemically induced carcinogenesis model.” They continued: “Stimulation of immune cells isolated from Peyer’s Patches [which are clusters of lymphoid follicles found in the intestine] showed a decrease in Thelper (Th)-1 IFN-γ secretion, while splenic Th1/Th17 inflammatory responses sharply increased,” researchers wrote. “A 100-day titanium dioxide treatment promoted colon microinflammation and initiated preneoplastic lesions.” The scientists concluded: “These data should be considered for risk assessments of the susceptibility to Th17-driven autoimmune diseases and to colorectal cancer in humans exposed to TiO2 from dietary sources.”

The brands of lithopone of the normal class, that of chemical manufacture, are marketed under such names as Ponolith, Beckton White, Jersey Lily White, Oleum White, Zinc Sulphide White, all of these being of domestic manufacture, and their composition is of the 30 per cent. zinc sulphide type. The German manufacturers and exporters of lithopone make use of fancy names for their brands and here are a few examples of these and the composition of the pigment:-

Stability and darkening:

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.