Zinc oxide is a naturally occurring mineral compound widely used in various products, particularly sunscreens, where it offers protection from ultraviolet radiation. Its particle size, specifically the “non-nano” distinction, significantly influences its application and perceived safety, and has become a focus for consumers and manufacturers.
Understanding Zinc Oxide
Zinc oxide (ZnO) is an inorganic compound formed from zinc and oxygen. While it occurs naturally as the mineral zincite, most zinc oxide used today is produced synthetically. It is a white, odorless powder nearly insoluble in water.
Zinc oxide has been used for centuries, with ancient Egyptians and Romans utilizing it in cosmetics, paints, and medicinal ointments. It is also a component in products like diaper rash creams, calamine lotions, rubber, ceramics, and paints. When applied topically, zinc oxide is generally considered safe.
The “Non-Nano” Distinction
The term “non-nano” refers to the size of zinc oxide particles. A nanometer (nm) is one-billionth of a meter. Particles classified as “nano” are typically smaller than 100 nanometers.
In contrast, “non-nano” zinc oxide particles are manufactured to be larger, generally 100 nanometers or greater in diameter. To illustrate, a human hair is approximately 80,000 to 100,000 nanometers wide, and a single sheet of paper is about 100,000 nanometers thick. This difference in particle size impacts how the material interacts with skin and the environment.
Why Particle Size Matters
Particle size is important due to concerns about skin absorption and environmental impact. Non-nano zinc oxide particles are too large to effectively penetrate the skin’s outer layer and enter the bloodstream. This ensures the compound remains on the skin’s surface, providing its intended benefit without systemic absorption.
Concerns have been raised regarding the potential for smaller, nano-sized particles to be absorbed into the body, although studies often show minimal penetration into the viable epidermis. The larger size of non-nano particles offers a clear distinction that addresses these absorption concerns. Beyond human health, particle size also affects environmental considerations. Non-nano zinc oxide is preferred for its reduced potential impact on aquatic ecosystems and marine life, as larger particles are less likely to be absorbed by marine organisms. Nanomaterials can accumulate in aquatic environments and have shown varying effects on aquatic organisms.
How Non-Nano Zinc Oxide Works
Non-nano zinc oxide functions as a “physical” or “mineral” sunblock, particularly in sunscreen formulations. Unlike chemical sunscreens that absorb ultraviolet (UV) radiation, non-nano zinc oxide creates a protective barrier on the skin’s surface. This barrier physically reflects and scatters harmful UVA and UVB rays away from the skin.
Its ability to reflect and scatter UV light provides broad-spectrum protection. This mechanism prevents the sun’s damaging rays from penetrating the skin, helping to prevent sunburn and other forms of sun damage. Its physical action offers immediate protection upon application, without needing time to be absorbed.