References

1. Properties: white powder, a mixture of zinc sulfide and barium sulfate.

This article discusses the discovery of phosphorescent lithopone on watercolor drawings by American artist John La Farge dated between 1890 and 1905 and the history of lithopone in the pigment industry in the late 19th and early 20th centuries. Despite having many desirable qualities for use in white watercolor or oil paints, the development of lithopone as an artists’ pigment was hampered by its tendency to darken in sunlight. Its availability to, and adoption by, artists remain unclear, as colormen's trade catalogs were generally not explicit in describing white pigments as containing lithopone. Further, lithopone may be mistaken for lead white during visual examination and its short-lived phosphorescence can be easily missed by the uninformed observer. Phosphorescent lithopone has been documented on only one other work-to-date: a watercolor by Van Gogh. In addition to the history of lithopone's manufacture, the article details the mechanism for its phosphorescence and its identification aided by Raman spectroscopy and spectrofluorimetry.

Lithopone was discovered in the 1870s by DuPont. It was manufactured by Krebs Pigments and Chemical Company and other companies.^[2] The material came in different seals, which varied in the content of zinc sulfide. Gold seal and Bronze seals contain 40-50% zinc sulfide, offering more hiding power and strength.^[3] Although its popularity peaked around 1920, approximately 223,352 tons were produced in 1990. It is mainly used in paints, putty, and in plastics.^[1]

The annual production capacity of high-grade rutile titanium dioxide has reached more than 400,000 tons. It is one of the largest TiO2 manufacturers in China at present. It has more than ten product brands of Taiohua, Jinxing and other brands, and its products are sold in more than 50 countries and regions around the world. It has long maintained the excellent performance of the second overall ranking in the domestic titanium dioxide industry.

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.

However, humans are not exposed to E171 in drinking water at any significant quantity over a long duration, so this potential effect is irrelevant to the human experience. It’s important to understand that a potential hazard is not the same thing as an actual risk. 

However, some experts and food regulators in other countries disagree – pointing to potential, serious health consequences and rising concerns about the additive. Starting August 7, for example, the use of titanium dioxide in food will be banned in the European Union.

FAQ – EFSA 2021 safety assessment of titanium dioxide (E171)

Historical references

Respiratory Exposure 

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Titanium dioxide R-996 is mainly used in powder coatings, water-based and solvent-based external coatings, high-grade color masterbatches, plastics, rubber, inks, high-grade paper and wax paper and leather upholstery fabrics, cosmetics, suitable for high-grade interior coatings, high-solid paints, Road marking paints, marine paints and inks, and also used in the plastics, rubber, paper and leather industries.