Zinc Oxide
Zinc Oxide is found in the Earth's crust as a natural mineral zincite. Most zinc is manufactured by the French process, in which the zinc is melted, vaporized, and cooled to produce zinc particles. Zinc Oxide has been recognized by the FDA as a Category 1 skin protectant that blocks UVB, UVAII, and UVAI rays to protect against photodamage including sunburn and photoaging.
Unfortunately, traditional zinc oxide is not cosmetically elegant to be used for total body sun protection due to its white and pasty texture. However, the newly available transparent micro-zinc oxide coated in the patented form of dimethicone overcomes these drawbacks. Micro-transparent zinc oxide transforms traditional granular particles of zinc oxide into a smooth, elegant formula that is completely transparent, thus ideal for wearing alone or under makeup or cosmetics. This transparent zinc oxide provides true UVA/UVB protection, uniformly shielding from 290 to 380 nanometers (nm).
Titanium Dioxide
Titanium, the ninth most common element in the Earth's crust, is a metal commonly found in plants and animals. It is the naturally occurring compound created when titanium reacts with the oxygen in the air.
Titanium Dioxide is used in sunscreens mainly due to its ability to reflect and scatter ultraviolet radiate. Moreover, Titanium Dioxide is a semiconducting material with very high refractive indices for all its crystalline forms, allowing it to scatter visible light. However, this high refractive index of titanium dioxide confers it with an opaque, cosmetically unappealing appearance upon topical application. Therefore, most formulations that are micronized do not cross the stratum cornea and confers broad-spectrum UV protection against both UVB and UVA.
Zinc Oxide and Titanium Dioxide
Physical sunscreens are considered safe ingredients for sunscreens and skincare by both the FDA and dermatologists. Experts often recommend them as an active ingredient for kids because it does not cause hormonal disruption and for people with sensitive skin or eczema.
According to the Skin Cancer Foundation, using physical sunscreens ingredients can help prevent skin cancer from occurring.
UV Protection Strength of Physical Sunscreen
Both titanium dioxide and zinc oxide offer total UVB protection; however, zinc oxide offers far more UVA protection than titanium dioxide.
• Titanium Dioxide is a common physical sunblock; it protects in the UV range from 290-340 nm. It protects against UVB radiation fully, but only protects against short UVA radiation (320-340 nm).
• Zinc Oxide uniformly covers from 290-380 nm, thus protecting against UVB (290-320 nm) and most of the UVA (320-400 nm). No other sunscreen ingredient provides broader protection.
These agents are not only effective against UV radiation but also protect against infrared radiation and visible light, a.k.a. blue light - a growing concern that stems from increased screen time. “Light within the blue visible spectrum has been shown to deeply penetrate the skin and promote premature aging, including sunspots and wrinkles.
Dangerous Effect of Using Nanoparticles of Zinc Oxide and Titanium Dioxide in Sunscreen
One of the biggest buzzwords in sunscreens is nanoparticles. The nanoparticles of these two compounds can enter the bloodstream and cause cytotoxicity, genotoxicity, and potential photocarcinogenecity. In addition, nanoparticles of ZnO, even at a much lower concentration, may induce inflammation by releasing inflammatory mediators, such as cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α.
Sunspheres and microencapsulations are newer technologies in the preparation of sunscreen formulation to avoid the use of nanoparticles.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3781714/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5677299/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4279726/