By May 20009 the FDA will be implementing new standards for sunscreen labeling and testing which will include UVA as well as UVB protection ratings. It will likely be patterned after the Australian system, considered the most advanced in the world.
There are 3 types of UV rays. UVA rays are the longest rays penetrating into the dermis. Often termed the "aging" rays, they are primarily responsible for premature aging and wrinkling. UVA rays do not burn, are not filtered by glass, do not change with altitude or atmosphere, are present all day and all year. They are not seasonal.
UVB rays are medium in length and do not penetrate the epidermis. These are the "burning" rays. UVB are strongest in the middle of the day, and are affected by season, altitude, and atmosphere. Both UVA and UVB rays can cause skin cancer.
UVC rays are the shortest rays and are largely filtered by the ozone layer.
The Australian sunscreen rating system is the only one in the world that currently requires rating for UVA protection, based on a 4 star system. In the U.S., sunscreens containing UVA protection are labeled as "broadspectrum" sun protection, though there is no rating for the level of protection. The FDA is likely to adopt the 4 star rating system as well as requiring the label "No UVA Protection" on sunscreens that do not offer UVA protection.
The present U.S. SPF rating only applies to UVB rays and measures how much exposure to rays are needed to burn the skin. Tests are performed using 2 mg of sunscreen on 1 sq cm of skin. This translates into .72 fl ozs. for a 5' person, 90 lbs, with a 30" waist and 1.5 fl ozs. for a 6'5" person, 225 lbs, with a 36" waist. The length of protection depends greatly on activity and reapplication. Studies indicate that people use 10%-30% of the recommended amount. SPF stands for "Sun Protection Factor" which will be changed to "Sunburn Protection Factor."
The following chart helps to understand how many rays are blocked:
There are both chemical and physical sunscreens. Chemical sunscreens absorb rays while physical sunscreens block them. There are many chemical sunscreens used world-wide, some of which have been deemed toxic and/or irritating to the skin. It is important to research your sunscreen ingredients for this reason.
The 2 physical sunblocks are Titanium Dioxide and Zinc Oxide. The benefit of these is that they aren't absorbed by your body but simply sit on the surface of your skin as a shield. They tend to be better for acne-prone and sensitive skin. The down side is that they tend to leave a white sheen and aren't as long-lasting as some of the more advanced chemical sunscreens. Our Cosmedix sunscreens only contain one or both of these physical sunblocks because they are guaranteed not to react chemically with peels or other skin products. Both Titanium Dioxide and Zinc Oxide offer UVB and UVA protection.
from Christine Oddo's presentation 3/26/09