What is sunscreen supposed to be doing? (Phil Cole/Getty Images)
Did you know that having more than five sunburns doubles a person’s risk of developing skin cancer in his or her lifetime? Sun exposure is the most preventable risk factor for two types of skin cancer: basal cell carcinoma and squamous cell carcinoma. [Editor’s Note: The relationship between malignant melanoma and sun exposure is far less certain.] [1]
A recent investigation of 1,000 brand-name sunscreens found that four out of five sunscreens contain chemicals that may have health hazards or do not adequately protect the skin from sun damage.
With no mandatory, comprehensive sunscreen standards in place, products vary widely in safety and effectiveness. More than 80 percent of marketed sunscreens in the United States claim to give UVA protection, but studies show that only about half of them actually do.
UVA and UVB are types of UV radiation emitted by the sun. Although the atmosphere’s ozone layer shields us from most of the sun’s rays, the UV light that is emitted may cause problems. However, both types of UV light contribute to premature skin aging, skin cancer, and other types of damage. In the dermis, the skin’s outermost layer, UV radiation causes collagen to break down at a higher rate than with just chronological aging.
SPF is a measure of how much UVB radiation is required to produce sunburn on protected skin (with sunscreen) relative to the amount of solar energy required to produce sunburn on unprotected skin. Contrary to what most people think, SPF is not directly related to time of solar exposure but to amount of solar exposure. For example, 1 hour at 9 a.m. versus 15 minutes at 1 p.m. may result in exposure to the same amount of solar energy.
So if SPF measures UVB protection, what measures UVA protection? The FDA has proposed a rule—which probably will not come into effect until 2009—that requires sunscreens to use a four-star system to rate levels of UVA protection as low, medium, high, or highest. This rating system is based on Persistent Pigment Darkening (PPD) and Protection Factor (PFA) UVA. PPD is the ability to prevent tanning when exposed to UVA light, which would not be required on labels. PFA is determined by the ratio of PPD on protected skin relative to unprotected skin, which will be required on labels.
Current FDA regulations allow a product to make a claim that it has UVA protection if it covers part of the UVA spectrum. Two types of skin cancers, basal and squamous cell cancer, are more common but less deadly. Basal cell cancer is the most common, and occurs in the deepest layer of epidermis, hair follicles, and sweat ducts. Squamous cell cancer occurs in the outer layer of skin, the epidermis.
More than 1 million unreported cases of basal cell or squamous cell cancers occur annually and continue to increase. Fortunately, most of these forms of skin cancer are highly curable.
In general, risk factors for all types of skin cancers include a history of sunburns, sunburning easily, natural blonde or red haired, using tanning booths, and occupational exposure to coal tar, arsenic compounds, or radiation.
Editor’s Reference:
[1] Does Sun Exposure Really Cause Malignant Melanoma?
http://en.epochtimes.com/news/8-6-21/72235.html
Jessica Poquiz is a Doctor of Pharmacy Candidate
Next week: Products to protect the skin
