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Ultraviolet (UV) Radiation and Your Health

Ultraviolet (UV) radiation is a type of light. Sunlight has UV rays, along with other kinds of rays. Some light bulbs give off UV rays, too. UV light bulbs are used in tanning beds and lamps, some nail dryers, machines used by dermatologists, and more.

Types of UV rays

There are 3 types of UV rays:

  • UVA. These rays go into the skin more deeply than UVB rays. They play a major part in skin aging and wrinkling. They also cause skin cell damage that can lead to cancer. 

  • UVB. These rays are the main cause of sunburn. They tend to damage the skin's outer layers. Exposure to these rays is linked to most skin cancers.

  • UVC. These are dangerous rays, but they don’t reach our skin. The Earth’s atmosphere absorbs UVC rays before they reach us.

How UV rays affect your health

In most people, UV rays activate a chemical in the skin called melanin. This is the skin's first defense against the sun. Melanin absorbs the dangerous UV rays that can do serious skin damage. This is the process that gives you a tan. A tan is a sign that your skin is trying to keep UV rays from damaging your skin.

But melanin can’t absorb all the UV rays. And some people don’t have much melanin in their skin. A sunburn happens when the amount of UV rays exceeds the protection that the skin's melanin can provide. Sunburn is damage to the skin. It causes pain, redness, and blistering.

Exposure to UV rays is linked to other harmful health conditions, too, such as:

  • Skin cancer. Millions of people are diagnosed with skin cancer in the U.S. each year. Skin cancer is more common as people get older. But skin damage from the sun starts at an early age and builds up over time. Protection should start in childhood to prevent skin cancer later in life.

  • Premature aging of the skin.  This is also called photoaging. It causes the skin to become thick and leathery over time. Other signs of photoaging include earlier-than-normal freckling, wrinkling, loss of collagen, and widening of small blood vessels in the skin. These changes can happen at younger ages and more quickly in people who regularly spend a lot of time in the sun or regularly used tanning beds or lamps. The skin may also develop brown spots (liver spots) in later years.

  • Cataracts and other eye problems. UV radiation exposure increases the risk of cataracts. This is when the lens of the eye becomes cloudy, making it hard for you to see. If not treated, cataracts can lead to blindness over time. Other eye changes from UV light can include eye damage, eye pain, and vision problems.

What is the UV Index?

The UV Index (UVI) is an official forecast from the National Weather Service. It estimates how much ultraviolet radiation will reach the Earth's surface when the sun is at its highest point in the day for most ZIP codes across the U.S. This information can help you plan outdoor events and know your level of sun exposure. It also gives you tips on how to help prevent sunburns.

The UVI also includes the effects of cloud cover on the forecast UV level. It notes the risk of overexposure to the sun's UV rays on a scale from 0 (low) to 11+ (extreme). The World Health Organization (WHO) uses a system of colors that correspond to UVI.

Understanding the UV Index

UV Index values

Color

Amount of risk

0 - 2

Green

Low. Low danger from unprotected sun exposure for the average person. But if you burn easily, cover up and use sunscreen with a sun protection factor (SPF) of at least 30. Wear sunglasses with UV protection on bright days.

3 - 5

Yellow

Moderate. A moderate risk of harm from unprotected sun exposure. Wear protective clothing, sunglasses, and a hat if you will be outside. Stay in shade around midday. Use sunscreen with at least SPF 30 and reapply every 2 hours, even on cloudy days. Wear sunglasses with UV protection.

6-7

Orange

High. A high risk of harm from unprotected sun exposure. Wear protective clothing, sunglasses, and a hat if you will be outside. Use sunscreen with at least SPF 30 and reapply every 2 hours, even on cloudy days. Reduce your time in the sun between 10 a.m. and 4 p.m. Wear sunglasses with UV protection.

8-10

Red

Very High. A very high risk of harm from unprotected sun exposure. Wear protective clothing, sunglasses, and a hat if you will be outside. Use sunscreen with at least SPF 30and reapply every 2 hours, even on cloudy days. Seek shade outdoors. Try to avoid the sun between 10 a.m. and 4 p.m. Wear sunglasses with UV protection.

11 +

Purple

Extreme. An extreme risk of harm from unprotected sun exposure. Follow all of the above suggestions to protect yourself from the sun. Wear protective clothing, sunglasses with UV protection, and a hat if you will be outside. Apply sunscreen with at least SPF 30 every 2 hours, even on cloudy days. Seek shade outdoors. Try to avoid the sun between 10 a.m. and 4 p.m.

Staying safe in the sun

For many people, a small amount of exposure to sunlight is fine. But too much can be dangerous. Keep track of the UV Index. Protect your skin with clothing and sunscreen. Wear sunglasses with UV protection. Take extra care around sand, water, and snow. They all reflect UV rays and give you more exposure. These steps will help you reduce your risks of cancer, premature aging of the skin, and harm to your eyes.              

Online Medical Reviewer: Jessica Gotwals BSN MPH
Online Medical Reviewer: Kimberly Stump-Sutliff RN MSN AOCNS
Online Medical Reviewer: Michael Lehrer MD
Date Last Reviewed: 3/1/2022
© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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