You may be taking a second look at your favorite candy after hearing this week's news about titanium dioxide. Recently, a lawsuit was filed against Mars, Inc. based on claims that the manufacturer's popular Skittles candy is unfit for human consumption. The class-action lawsuit, filed in U.S. District Court for the Northern District of California in mid-July, alleged that the candy contained heightened levels of a known toxin called titanium dioxide — a food additive that the company previously pledged to phase out from their products in 2016, according to the Center for Food Safety.

No acute effects of nano-sized TiO₂ were observed in Danio rerio (zebrafish) embryos. Exposure of rainbow trout to TiO₂ NPs triggered lipid peroxidation, influence on the respiratory tract, disturbance in the metabolism of Cu and Zn, induction of intestinal erosion  and accumulation in kidney tissue. Linhua et al. exposed juvenile carp to 100 and 200 mg/ml of particles and TiO₂ observed no mortality. However, the fish suffered from oxidative stress and pathological changes in gill and liver. In the infaunal species Arenicola marina, exposure to TiO₂ NPs in sediment caused sub-lethal effects including decrease in casting rate and increase in cellular and DNA damage. Aggregated particles were visible in the lumen of the gut, but no uptake through the gut or the skin was observed.

Titanium dioxide is produced in two main forms. The primary form, comprising over 98 percent of total production, is pigment grade titanium dioxide. The pigmentary form makes use of titanium dioxide’s excellent light-scattering properties in applications that require white opacity and brightness. The other form in which titanium dioxide is produced is as an ultrafine (nanomaterial) product. This form is selected when different properties, such as transparency and maximum ultraviolet light absorption, are required, such as in cosmetic sunscreens.

4.Used as a white pigment, the hiding power is second only to titanium dioxide, but stronger than zinc oxide. The hiding power increases as the ZnS content increases, and the light resistance also improves, but the acid resistance decreases.