Dermatology Northwest
Carolyn I. Hale, M.D.
Physician and Surgeon
Board Certified Dermatologist
Joel A. James, PA-C
Education Page
SHINING LIGHT ON ULTRAVIOLET RADIATION
Ultraviolet radiation is composed of three wavelengths: UVA, UVB and UVC. While UVC isn't a concern for skin cancer, UVA and UVB play different roles when it comes to tanning, burning, and photoaging.
With the ongoing debate about the best way to get Vitamin D and the controversy surrounding tanning beds, there is a huge amount of misinformation surrounding ultraviolet radiation (UV). However, one thing is clear: UV radiation is the main factor responsible for skin cancers, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and possibly melanoma. 
UVA is long wavelength UV and accounts for up to 95 percent of the solar UV radiation reaching the Earth's surface. It can penetrate into the deeper layers of the skin and has for years been thought to play a major part in skin aging and wrinkling. Importantly, recent studies strongly suggest that it may also initiate and exacerbate the development of skin cancers. UVA rays are present during all daylight hours and throughout the winter months. Although UVA rays are less intense than UVB rays, they are present all year round and depending upon the time of the year, can be 30 to 50 times more prevalent than UVB rays. Furthermore, UVA radiation can penetrate glass and clouds. Thus, we are exposed to large doses of UVA throughout our lifetime.
UVB is the middle-range of UV. It responsible for burning, tanning, acceleration of skin aging and plays a very key role in the development of skin cancer. The intensity of UVB varies by season, location and time of day. The most significant amount of UVB hits the U.S. between 10 AM and 4 PM between April and October. UVB rays do not penetrate glass.
UVC is the shortest and highest energy UV, however, since it is filtered by the ozone, these wavelengths do not reach the earth's surface and do not contribute to skin damage in humans.
While the differences between UVB and UVA need to be explored further, it's proven that exposure to the combination of UVB and UVA is a powerful attack on the skin. It can create irreversible damage that ranges from sunburn to premature aging to skin cancer. Protection from these rays is the only way to avoid these problems.
In order to get adequate protection against both UVA and UVB, you should select a sunscreen that provides multispectrum protection, broad-spectrum protection or UVA/UVB protection – not just a sunscreen with a high SPF (UVB) rating.
Common FDA-approved active ingredients in sunscreen include:
• UVB absorbers/blockers: Padimate O (Octyldimethyl PABA), Homosalate, Octisalate (Octyl salicylate), Octinoxate (Octyl methoxycinnamate or OCM)
• UVA absorbers/blockers: Avobenzone (Parsol 1789), Zinc Oxide, Ecamsule (Mexoryl)
• UVA and UVB absorbers/blockers: Octocrylene, Titanium Dioxide, Zinc Oxide
Article written by SkinCancer Foundation
Education Links
American Academy of Dermatology Education Page
A great tool from AAD (More information on various skin conditions)
Useful information available at skincancer.org
Online instruction for self-skin exams
ABCD'S of Melanoma Detection
National Psoriasis Foundation
National Alopecia Areata Foundation
National Eczema Foundation
Acne