Medical Dermatology

Ultraviolet Radiation

Everything You Need to Know about UVR & Protecting Yourself

Ultraviolet solar radiation (UVR) causes 90% of all skin cancers and is linked to sunburns and photo- aging. It causes broken blood vessels; wrinkles; rough, leathery skin and brown spots. It causes premalignant lesions and skin cancers such as actinic (solar) keratoses, basal cell carcinomas, squamous cell carcinomas, malignant melanomas, and others. It also alters DNA, suppresses the immune system and is the main cause of cataracts.

There are three types of UVR but only two that currently concern us:

UVA rays are long wavelengths that penetrate window glass and travel more deeply into the skin. They constitute more than 90% of all ultraviolet rays. UVA is present in the same amount all day long, all year long and is independent of altitude, atmospheric or weather conditions. It bears major responsibility for aging of the skin, most skin cancers including malignant melanoma, and suppression of the immune system. About 50% of UVA exposure occurs in the shade.

UVB causes most sunburns, synthesizes vitamin D and results in delayed tanning. UVB is prevalent only when the sun is high in the sky – between 10 AM and 4 PM. UVB exposure increases 8-10% for every 1000 feet above sea level, so it is very important to use protection at higher elevations. Since snow reflects up to 80% of UV, it nearly doubles the exposure.

Important Statistics

One in five Americans will get skin cancer in his/her lifetime.
Actinic keratoses (premalignant lesions) are the most prevalent cell abnormality followed by basal cell carcinoma (over 1 million annually in the US), squamous cell carcinoma (>200,000), and malignant melanoma. (~70,000 invasive and >46,000 limited to the top layer of skin).
A recent study of 1621 Australians found that regular use of sunscreens reduced the risk of malignant melanoma by 50-73%.

In the US, people sitting on the left side of the car receive approximately 6 times the dose of UV radiation on the left side of the head, neck, arm and hand as compared to the right side. As would be expected there are more basal cell, squamous cell and melanoma skin cancers on the left side of the face and left arm due to driving. This can be lessened by regular sunscreen use.

Tips to Protect Yourself

While UVR peaks in the summer, more than half the annual total is emitted during the rest of the year. Basic, daily, year-round, sustained protection is the key. There is no such thing as a healthy tan. Tanning is the skin’s response to DNA cellular damage.

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