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Sun Exposure
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Natural Radiation:This page provides an overview of how the sun’s energy is needed for survival and how various types of ultraviolet radiation that can be dangerous to our skin.
On this page:
Overview
While some exposure to sunlight can be enjoyable and healthful, too much can be dangerous. Ultraviolet radiation (UV) comes naturally from the sun. UV is divided into three different categories based on wavelength. Wavelength is the distance between two successive peaks of a wave. UV wavelengths are measured in nanometers (nm) or one billionth of a meter. The shorter the wavelength the higher the energy.
- UVA wavelengths (315-400 nm) have the longest wavelengths, and are only slightly affected by ozone levels. Most UVA radiation is able to reach Earth's surface and can contribute to sunburn, skin aging, eye damage, and can suppress your immune system.
- UVB wavelengths (280-325 nm) are strongly affected by ozone levels. Decreases in stratospheric ozone mean that more UVB radiation can reach Earth's surface,causing sunburns, snow blindness, immune system suppression, and a variety of skin problems including skin cancer and premature aging.
- UVC wavelengths (180-280 nm) have the shortest wavelengths, and are very strongly affected by ozone levels. Virtually all UVC radiation is absorbed by ozone, water vapor, oxygen and carbon dioxide before reaching Earth’s surface.
Therefore, the UV radiation reaching Earth’s surface is largely composed of UVA with some UVB. Almost half the daytime total UV radiation is received between the hours of 10 a.m. an 4 p.m. Even on a cloudy day, you can get sunburned because of UV radiation.
Caution
Even on a cloudy day you can get sunburn from UV radiation.One in five Americans develops skin cancer, and one person dies from this disease every hour. The incidence of melanoma, the most serious type of skin cancer, is increasing faster than most other forms of cancer. Children are of particular concern since most of the average person's lifetime sun exposure occurs before the age of 18. There are simple protective measures that you can take to limit exposure to UV rays.
Who is protecting you
U.S. Environmental Protection Agency (EPA)
EPA sponsors the SunWise program, which teaches the public how to protect themselves from overexposure to the sun. Through the use of classroom-based, school-based, and community-based components, SunWise seeks to develop sustained sun-safe behaviors in schoolchildren.
National Oceanic and Atmospheric Administration (NOAA)
EPA worked with the NOAA’s National Weather Service to develop the UV Index, which predicts the next day's ultraviolet radiation levels on a 1-11+ scale, helping people determine appropriate sun-protective behaviors.
World Health Organization (WHO)
The World Health Organization revised guidelines for reporting the UV Index. The United States and Canada both adopted these guidelines and applied them to their current UV Indexes.
U.S. National Institutes of Health (NIH)
The National Cancer Institute provides prevention, screening, and treatment information for skin cancer. Together with EPA and the Centers for Disease Control and Prevention, the NIH researches methods to protect against the sun’s harmful rays, and provides helpful information to the public.
U.S. Food and Drug Administration (FDA)
FDA establishes rules that govern the makers of sunscreens, particularly product labeling and advertising. FDA ensures that the Sun Protection Factor (SPF) for sunscreen is clearly written on its label, and that consumers clearly understand what SPF means.
What you can do to protect yourself
- Limit Time in the Midday Sun: The sun's rays are strongest between 10 a.m. and 4 p.m., so try to avoid overexposure to the sun during those hours when possible, even in winter and especially at higher altitudes.
- Seek Shade: Shade is a good source of protection, but keep in mind that shade structures (e.g., trees, umbrellas, canopies) do not offer complete sun protection.
- Wear a Hat: Wide brimmed hats offer good sun protection to areas particularly prone to overexposure to the sun (i.e., eyes, ears, faces, and necks).
- Cover Up: Wear tightly woven, loose-fitting, and full-length clothing.
- Wear Sunglasses that Block 99-100% of UV Radiation: Sunglasses that provide 99-100% UVA and UVB protection greatly reduce sun exposure that can lead to cataracts and other eye damage.
- Always Use Sunscreen: Apply a broad spectrum sunscreen with a Sun Protection Factor (SPF) of 15 or higher liberally on exposed skin. Reapply every 2 hours, or after working, swimming, playing, or exercising outdoors.
- Watch the UV Index: The UV Index provides important information to help people plan outdoor activities in ways that prevent overexposure to the sun.
Regardless of your exposure to UV rays, conduct a monthly skin self-exam looking for any abnormalities (like bumps or sores that don't heal) or moles that have changed size, color or shape. Be sure to check all areas. Have a friend or family member check your back. Visit your physician or a dermatologist to get annual exams. If caught early, most cases of skin cancer can be cured.
Resources
| SunWise Program 15 September 2005. U.S. Environmental Protection Agency This site uses classroom-based, school-based, and community-based components to teach the public how to protect themselves from overexposure to the sun. |
| SunWise Program:
UV Index 15 September 2005. U.S. Environmental Protection Agency This page provides information about what the UV Index is, how it’s calculated, and other relevant information and resources. |
| "The
SunWise School Program Guide" 15 September 2005. U.S. Environmental Protection Agency This document is designed to provide school administrators, teachers, nurses, and other childhood caregivers with a general overview of EPA’s SunWise Program. |
| "Trying
to Look SUNsational? Complexity Persists in Using Sunscreens" 13 June 2000. U.S. Food and Drug Administration This page discusses the scientific debate about skin damage resulting from UV radiation exposure and whether current sunscreens provide adequate protection and how best to label these over-the-counter products. |
How is
the Public Protected from Radiation?
 10 December 2002 National Safety Council This page provides a brief description about the importance of controlling exposure to ultraviolet radiation from the sun especially for children. |
| More
WHO Member States Unite in Fight Against Skin Cancer Caused
By Excessive Exposure to UV Radiation (PDF) (2pp, 59Kb )
27 May 2004. World Health Organization. This page is a press release about more countries adopting the Global Solar UV Index to educate citizens about the dangers of overexposure to ultraviolet radiation. |
| Skin
Cancer 15 September 2005. U.S. National Institutes of Health, National Cancer Institute This page provides information about skin cancer treatment and prevention. |
| UV Radiation Page 11 August 2005. U.S. National Oceanic and Atmospheric Administration This page provides information about what UV radiation is, measurement instruments, monitoring systems and networks, other resources, and more. |
| Global
Solar UV Index: A Practical Guide (PDF) (18pp, 429Kb )
WHO/SDE/OEH/02.2 2002. A Joint Recommendation of the World Health Organization, World Meteorological Organization, United Nations Environment Programme, and the International Commission on Non-Ionizing Radiation Protection. |