Topics for this column are selected one of two ways: either something important has happened such as a new regulation, or a number of phone calls have been received on a subject. The latter, while a close second to the first, indicates the need to more fully explain the complex issues of regulation. Based on a number of recent phone calls, this column will discuss titanium dioxide (TiO2).
TiO2 is the most frequently used ingredient in cosmetics after water (aqua), fragrance (parfum), methylparaben, propylparaben, glycerin and propylene glycol, according to the U.S. Food and Drug Administration’s (FDA) Voluntary Cosmetic Registration Program. It is a popular UV filter in sizes ranging from pigment grade, which the FDA originally approved in 1978, to micro-size grades and nano-size grades. It is the whitest pigment known and occurs in ores such as ilmenite (most common), leucoxene, rutile and anatase. Ilmenite is gray-black in color and also contains iron oxides, magnesium and manganese. No naturally occurring minerals containing titanium are allowed in personal care products, so all TiO2 is synthetically produced.
There are two common methods to produce TiO2—the sulfate process and the chloride process. Almost all grades in the cosmetic industry are produced with the chloride process, which results in a whiter raw material as opposed to the yellowish cast that is typical of the sulfate method. In the chloride process, the crude ore containing at least 70% TiO2 is reduced with carbon and oxidized with chlorine to give titanium tetrachloride. This titanium tetrachloride is then distilled and re-oxidized in a pure oxygen flame or plasma at 1,500–2,000°C to give pure TiO2 while also regenerating chlorine.