Because of their small size, nanoparticles may have unique physical and chemical properties. These properties may cause them to interact with living systems differently than larger materials with the same chemical composition (also known as bulk materials).

Barium sulfide is produced by carbothermic reduction of barium sulfate. Zinc sulfate is obtained from a variety of zinc products, often waste, by treatment with sulfuric acid.

Titanium dioxide can amplify and brighten white opacity because of its exceptional light-scattering properties. In food and drugs, these properties help to define colors clearly and can prevent products from UV degradation. 

Drobne et al. used the terrestrial arthropod Porcellio scaber as a test organism for determining the cytotoxic effect of TiO₂ NPs (anatase). The animals were exposed to TiO₂ NPs of two different sizes (25 nm and 75 nm) in the concentration range 10–1000 μg TiO₂/g dry food for 3 to 14 days. No adverse effects, such as mortality, body weight changes or reduced feeding, were observed. In fact, quite the opposite, an enhanced feeding rate, food absorption efficiency and increase in catalase activity were observed. The intensity of these responses appeared to be time- but not dose-dependent. It should also be noted that the concentrations tested in this study were much higher than the predicted concentration (4.8 μg/g soil) at high emission scenario of nano-sized TiO₂. Using the same test organism another group showed that exposure to TiO₂ NPs induced destabilization of cell membrane in the epithelium of digestive glands isolated from exposed animals. They also showed that this effect can be observed after just 30 minutes of exposure.

Potential hazards of oral exposure to TiO₂ NPs 

In a study published in the journal Environmental Toxicology and Pharmacology in 2020, researchers examined the effects of food additives titanium dioxide and silica on the intestinal tract by grouping and feeding mice three different food-grade particles — micro-TiO2, nano-TiO2, and nano-SiO2.  With all three groups, researchers observed changes in the gut microbiota, particularly mucus-associated bacteria. Furthermore, all three groups experienced inflammatory damage to the intestine, but the nano-TiO2 displayed the most pronounced changes. The researchers wrote: “Our results suggest that the toxic effects on the intestine were due to reduced intestinal mucus barrier function and an increase in metabolite lipopolysaccharides which activated the expression of inflammatory factors downstream. In mice exposed to nano-TiO2, the intestinal PKC/TLR4/NF-κB signaling pathway was activated. These findings will raise awareness of toxicities associated with the use of food-grade TiO2 and SiO2.”

In sunscreen, titanium dioxide is used as a barrier to keep the sun's ultraviolet (UV) rays from damaging your skin. It's processed into much smaller particles than what goes into food, called nanoparticles. In this form, it becomes transparent, and also absorbs UV light so it doesn't reach your skin.

The main food categories contributing to dietary exposure of E171 are fine bakery wares, soups, broths and sauces (for infants, toddlers and adolescents); and soups, broths, sauces, salads and savoury based sandwich spreads (for children, adults and the elderly). Processed nuts are also a main contributing food category for adults and the elderly.