Zinc Sun Protection and UV Rays

SPF, or Sun Protection Factor, is a measurement of how well a sunscreen will protect skin from UVB rays, the kind of radiation that causes sunburn and is thought to contribute to some types of skin cancer.

Example: If your skin would normally burn after 10 minutes in the sun, applying an SPF 15 sunscreen would allow you to stay in the sun without burning for approximately 150 minutes (a factor of 15 times longer). This is a rough estimate and depends on skin type, the intensity of sunlight, and the type of activity. But SPF isn’t quite that simple. The scale is not linear: SPF 30 actually only blocks 5% more UVB radiation than SPF 15. For best protection, experts do recommend a minimum SPF rating of 15, and applying sunscreen generously and frequently.

The SPF rating only tells you only about UVB protection, not about harmful UVA rays. UVA is the wavelength of sunlight that penetrates deeper into the skin without causing surface burning, but has the potential to release free radicals and perhaps cause skin melanoma and photo aging. Always choose sun protection that is broad spectrum - blocks both UVB and UVA wavelengths. Just because a sunscreen has a high SPF, it does not mean you are being protected from damaging UVA rays.

Zinc moisturizers and sunblocks with high levels SPF (15 or more) are broad spectrum: strong enough to prevent burning for a reasonable length of time with the power to block UVA radiation — something that many higher SPF products cannot match!
UVA Protection

UVA: Long-wave solar rays of 320-400 nm. Penetrate the skin more deeply (into the Dermis, 2nd layer of skin); cause photo aging, actinic damage (wrinkled, leathery, variously pigmented skin); and can contribute to skin cancers including melanoma. Rays are the same strength year-round.
UVB: Short-Wave solar rays of 290-320 nm. Penetrate only the epidermis; cause sunburn; and considered to be the main cause of basal and squamous cell carcinomas, as well as a significant factor in melanomas. Different strengths depending on Sun’s location, and can be lessened when deflected by clouds.

UVC: Reflected by the Ozone layer, does not reach the Earth.

Critical Wavelength: an international rating system for UVA protection. The point at which the sunscreen allows 10% of the rays to penetrate is defined as Critical Wavelength. A sunscreen with a critical wavelength over 370nm is considered by the FDA to provide excellent UVA protection.

Links to some helpful web sites regarding sun protection.
•    The Environmental Working Group’s “Special Investigation on Nanotechnology & Sunscreens”
•    The Environmental Protection Agency’s “Sunwise: The Burning Facts.”
•    The “Cosmetic Safety Database” – for safety and efficacy of all your personal care products