By David Liu, PHDSaturday, May 5, 2012 (foodconsumer.org) -- Zinc is an important nutrient that humans need. But zinc salts in the form of nanoparticles such as zinc oxide which is commonly used in multivitamins by the dietary supplements industry or as a fortifying agent in foods, can cause harm to normal cells.Vyom Sharma of CSIR-Indian Institute of Toxicology Research in Uttar Pradesh, India and colleagues conducted a study and found that when exposed to 14 to 20 micrograms per mL zinc oxide nanoparticles for 12 hours, liver cells were more likely to die than those that were not exposed to the nanoparticles.The researchers further found that zinc nanoparticles induced apoptosis that killed the exposed liver cells and caused DNA damage, which was found mediated by oxidative stress. DNA damage is the cause for cancer development.The study was released in the journal Apoptosis.Here are some applications of zinc oxide cited from wikipedia

The applications of zinc oxide powder are numerous, and the principal ones are summarized below. Most applications exploit the reactivity of the oxide as a precursor to other zinc compounds. For material science applications, zinc oxide has high refractive index, high thermal conductivity, binding, antibacterial and UV-protection properties. Consequently, it is added into materials and products including plastics, ceramics, glass, cement, rubber, lubricants, paints, ointments, adhesive, sealants, pigments, foods, batteries, ferrites, fire retardants, etc.

Rubber manufacture

About 50% of ZnO use is in the rubber industry. Zinc oxide along with  stearic acid is used in the vulcanization of rubber ZnO additive also protect rubber from fungi (see medical applications) and UV light.

Concrete industry

Zinc oxide is widely used for concrete manufacturing. Addition of ZnO improves the processing time and the resistance of concrete against water.

Medical

Zinc oxide as a mixture with about 0.5% iron(III) oxide (Fe₂O₃) is called calamine and is used in calamine lotion. There are also two minerals, zincite and hemimorphite, which have been historically calledcalamine. When mixed with eugenol, a ligand, zinc oxide eugenol is formed, which has applications as a restorative and prosthodontic in dentistry.

Reflecting the basic properties of ZnO, fine particles of the oxide have deodorizing and antibacterial properties and for that reason are added into materials including cotton fabric, rubber, and food packaging. Enhanced antibacterial action of fine particles compared to bulk material is not intrinsic to ZnO and is observed for other materials, such as silver. This property is due to the increased surface area of the fine particles.

Zinc oxide is widely used to treat a variety of other skin conditions, in products such as baby powder and barrier creams to treat diaper rashes, calamine cream, anti-dandruff shampoos, and antisepticointments. It is also a component in tape (called "zinc oxide tape") used by athletes as a bandage to prevent soft tissue damage during workouts.

Zinc oxide can be used in ointments, creams, and lotions to protect against sunburn and other damage to the skin caused by ultraviolet light (see sunscreen). It is the broadest spectrum UVA and UVB reflector that is approved for use as a sunscreen by the FDA, and is completely photostable. When used as an ingredient in >sunscreen, zinc oxide sits on the skin’s surface and is not absorbed into the skin, and blocks both UVA (320–400 nm) and UVB (280–320 nm) rays of ultraviolet light. Because zinc oxide (and the other most common physical sunscreen, titanium dioxide) are not absorbed into the skin, they are nonirritating, nonallergenic, and non-comedogenic.

Many sunscreens use nanoparticles of zinc oxide (along with nanoparticles of titanium dioxide) because such small particles do not scatter light and therefore do not appear white. Although there has been concern that they might be absorbed into the skin, comprehensive reviews of the medical literature have not uncovered any risk.

Cigarette filters

Zinc oxide is a constituent of cigarette filters for removal of selected components from tobacco smoke. A filter consisting of charcoal impregnated with zinc oxide and iron oxide removes significant amounts of HCN and H₂S from tobacco smoke without affecting its flavor.

Food additive

Zinc oxide is added to many food products, including breakfast cereals, as a source of zinc, a necessary nutrient. (Zinc sulfate is also used for the same purpose.) Some prepackaged foods also include trace amounts of ZnO even if it is not intended as a nutrient.

Pigment

Zinc white is used as a pigment in paints and is more opaque than lithopone, but less opaque than titanium dioxide. It is also used in coatings for paper. Chinese white is a special grade of zinc white used in artists' pigments. It is also a main ingredient of mineral makeup.

Coatings

Paints containing zinc oxide powder have long been utilized as anticorrosive coatings for metals. They are especially effective for galvanized iron. Iron is difficult to protect because its reactivity with organic coatings leads to brittleness and lack of adhesion. Zinc oxide paints retain their flexibility and adherence on such surfaces for many years.

ZnO highly n-type doped with Al, Ga, or In is transparent and conductive (transparency ~90%, lowest resistivity ~10⁻⁴ Ω·cm). ZnO:Al coatings are used for energy-saving or heat-protecting windows. The coating lets the visible part of the spectrum in but either reflects the infrared (IR) radiation back into the room (energy saving) or does not let the IR radiation into the room (heat protection), depending on which side of the window has the coating.

Plastics, such as polyethylene naphthalate (PEN), can be protected by applying zinc oxide coating. The coating reduces the diffusion of oxygen with PEN. Zinc oxide layers can also be used onpolycarbonate (PC) in outdoor applications. The coating protects PC form solar radiation and decreases the oxidation rate and photo-yellowing of PC.

Corrosion prevention in nuclear reactors

Main article: Depleted zinc oxide

Zinc oxide depleted in the zinc isotope with the atomic mass 64 is used in corrosion prevention in nuclear pressurized water reactors. The depletion is necessary, because Zn is transformed into radioactive Zn under irradiation by the reactor neutrons.