Facts About Ultraviolet Radiation

At a glance

Ultraviolet (UV) radiation is a form of non-ionizing radiation that is emitted by both natural and artificial sources. There are both benefits and risks to UV radiation. You should always protect yourself from over-exposure to reduce your risk of sunburn, premature aging, and skin cancer.

The sun shining brightly in the sky.

The basics

Ultraviolet (UV) radiation is a form of non-ionizing radiation that is emitted by the sun and artificial sources. The beneficial effects of UV radiation include the production of a vital nutrient, vitamin D. However, overexposure may present risks. Sunburn, premature aging, and skin cancer are all risks to overexposure. Keeping you and others protected from UV radiation is an important year-round.

Common Questions

  • Our natural source includes:
    • The sun
  • Some artificial sources include:
    • Tanning beds
    • Mercury vapor lighting (often found in stadiums and school gyms)
    • Some halogen, fluorescent, and incandescent lights
    • Some types of lasers

UV radiation is classified into one of three primary groups: ultraviolet A (UVA), ultraviolet B, (UVB) and ultraviolet C (UVC). This grouping is based on the measure of their wavelength, which is measured in nanometers (nm= 0.000000001 meters or 1×10-9 meters).

Wave Type


Absorption Level


315-400 nm

Not absorbed by the ozone layer


280-315 nm

Mostly absorbed by the ozone layer, but some does reach the Earth’s surface


100-280 nm

Completely absorbed by the ozone layer and atmosphere

All UVC and most UVB radiation is absorbed by the earth’s ozone layer, so nearly all of the ultraviolet radiation received on Earth is UVA. Even though UVA radiation is weaker energy than UVB, it penetrates deeper into the skin and is more constant throughout the year. Because UVC radiation is absorbed by the earth’s ozone layer, it does not pose as much of a risk. UVC produced by germicidal UV lights, however, can be harmful from human exposure.


  • Beneficial effects of UV radiation include the production of vitamin D, a vitamin essential to human health. Vitamin D helps the body to absorb calcium and phosphorus from food and assists in bone development. The World Health Organization (WHO) recommends 5 to 15 minutes of sun exposure 2 to 3 times a week.
  • Artificial forms of UV radiation used with some topical medications that increase UV sensitivity are used to treat patients with certain diseases who have not responded to other therapies. Artificial forms of UV radiation include lasers, lamps, or a combination of these devices. A trained healthcare professional uses a procedure called phototherapy to treat the following health conditions:
    • Rickets
    • Psoriasis
    • Eczema
    • Vitiligo
    • Lupus


  • Sunburn is a sign of short-term overexposure.
  • Premature aging and skin cancer are side effects of long-term UV exposure.
  • Some oral and topical medicines, such as antibiotics, birth control pills, and benzoyl peroxide products, as well as some cosmetics, may increase skin and eye sensitivity to UV in all skin types.
  • UV exposure increases the risk of potentially blinding eye diseases, if eye protection is not used.
  • Overexposure to UV radiation can lead to serious health issues, including cancer. Skin cancer is the most common cancer in the United States.

The two most common types of skin cancer are basal cell cancer and squamous cell cancer. Typically, they usually form on the head, face, neck, hands, and arms because these body parts are the most exposed to UV radiation. Most cases of melanoma, the deadliest kind of skin cancer, are caused by exposure to UV radiation.

Anyone can get skin cancer, but is more common in people who

  • Spend a lot of time in the sun or have been sunburned
  • Have light-color skin, hair and eyes
  • Have a family member with skin cancer
  • Are over age 50

Changes in your skin are the most common signs of skin cancer. Learn more about the symptoms of skin cancer.

Keeping yourself and others protected from UV radiation is important year round, not just at the beach or during the summer months.

Protect yourself from UV radiation

  • Stay in the shade, especially during midday hours.
  • Wear clothes that cover your arms and legs.
  • Wear a hat with a wide brim to shade your face, head, ears, and neck.
  • Wear sunglasses that wrap around and block both UVA and UVB rays.
  • Use sunscreen with sun protection factor (SPF) 15 or higher, and both UVA and UVB protection.

Certain types of glass and plastics can be used to block UV light, especially UVC.

The UV Index scale helps us understand how harmful UV radiation can be on a given day. This useful tool forecasts the strength of the sun's harmful rays. Remember, the higher the number, the greater chance of overexposure leading to health concerns.


Basic Information about Skin Cancer

This web site provides basic information about the health effects of ultraviolet radiation and the difference between UVA, UVB, and UVC.

National Institute for Occupational Safety and Health (NIOSH) Hazards to Outdoor Workers: UV Radiation

Provides information about the risks of UV radiation to outdoor workers, symptoms of sunburn and first aid tips. NIOSH also provides a listing of recommendations for protection from UV radiation that employers can distribute to workers who perform duties outdoors.

Travelers Health –Yellow Book: Chapter 2, the Pre-Travel Consultation Sunburn

Provides information for travelers about overexposure to the sun, health risks from UV rays, and preventive actions that travelers can take to avoid overexposure.

Skin Cancer Prevention Progress Report

In July 2014, the Office of the Surgeon General released The Surgeon General's Call to Action to Prevent Skin Cancer, establishing skin cancer prevention as a high priority for our nation. The "Skin Cancer Prevention Progress Report" summarizes recent prevention efforts and highlights new data, developments, and success stories following the Call to Action.

Artificial Tanning Sunbeds: Risk and Guidance

While the World Health Organization (WHO) does not recommend the use of UV tanning devices for cosmetic purposes, it is recognized that sunbeds continue to be available to the public. This practical guide, prepared by Craig Sinclair, WHO, is intended for government health authorities, to assist them in the development of public health policy in relation to sunbeds.

Food and Drug Administration

In the United States, the Food and Drug Administration (FDA) regulates tanning beds and other devices that can produce UV light. The FDA classifies these products as medical devices and are subject to performance standards.