Facebook Pixel

Ultraviolet Rays - How Much is Safe?

Rate This
Sunburn related image Photo: Getty Images

Ultraviolet (UV) light and rays cannot be seen by the human eyes. This is because UV light has shorter wavelengths than visible light. Although much has been talked about in regards to UV rays causing damage to the skin leading to sunburns and prolonged and repeated exposures leading to incidences of skin cancer, only a few of us are aware of the damage UV rays can do to our vision. However, there is no need for panic since only some ultraviolet waves from the sun penetrate Earth's atmosphere; most of them are blocked from entering by various gases like ozone. (Source: National Aeronautics And Space Administration, NASA; Report Title: The Electromagnetic Spectrum; NASA Official: Ruth Netting; Last Updated: March 27th, 2007; URL: http://science.hq.nasa.gov/kids/imagers/ems/uv.html)

The other ways UV rays can cause damage to vision include temporary blindness, hazy vision, development of cataract and pain. So, is there a way to know how much UV radiation is safe for us?

Fortunately, yes. Scientists have devised an indexing system that indicates how long a person can expose themselves to the sun’s light on a given day before the possibility of damage sets in. The words "on a given day" mean that UV radiation intensity is not the same every day and may differ depending on:

• Cloud spread
• Thickness of ozone layer
• Time of day
• Earth’s surface characteristics
• Season
• Distance from Equator

The UV index is an international system of measurement of the strength or intensity of the UV radiation at around noon and point on the globe. It is measured in watts per meter square of Earth surface or w/m2. The measured values are translated to absolute numbers which are easy for people to read and understand the implications of.

Values range from 0 to 11+. Zero radiation essentially means night time and no radiation from UV rays and 11+ indicates extreme radiation and risk of harm from unprotected sun exposure; this is especially common around noon. Here is a look at what the index readings mean:

0-2: Low Risk – Use sunscreen if there is snow or you are in a place with less greenery or are very fair skinned. Wear dark glasses if the day is bright with no cloud cover.

3-5: Little Risk – Do not go unprotected into the sunlight for long. Use an SPF 30+ sunscreen or a hat or umbrella around the noon time.

6-7: High Risk – The sun can cause sunburns to the skin. Use SPF 30+ liberally and every hour. Avoid stepping out between 11 a.m. and 4 p.m. If you must venture out then seek shade, and cover up with a hat and sunglasses.

8-10: Very High Risk – Same advice as for indexing of 6-7.

11+: Extreme Risk/ Dangerous – Here the risk of burn and eye damage are so high that the damage may happen quickly. For this reason protection is a must even for short outside trips. Use a higher than 30+ SPF on skin and wear UV filtering glasses. Make the trip short.

(Source: Canadian Centre For Occupational Health and Safety; Report Title: Ultraviolet Radiation; Last Updated: July 27th, 2005; URL: http://www.ccohs.ca/oshanswers/phys_agents/ultravioletradiation.html)

The best way to combat UV rays is with physical or mechanical protection of the body such as using an umbrella or hat, sunglasses or staying in shaded areas.
U.S residents may want to check UV Index reading for your area on a particular day by visiting the Environment Protection Agency’s (EPA) website titled SunWise Program: http://www.epa.gov/sunwise/uvindex.html


Reviewed July 4, 2011
by Michele Blacksberg R.N.
Edited by Alison Stanton

Mamta Singh is a published author of the books Migraines for the Informed Woman (Publisher: Rupa & Co. URL: http://www.amazon.com/Migraines-Informed-Woman-Tips-Sufferer/dp/8129115174/ref=sr_1_2?ie=UTF8&s=books&qid=1298990756&sr=1-2), the upcoming Mentor Your Mind (Publisher: Sterling Publishers) and The Urban Woman’s Integrated Fitness Guide (Publisher: Hay House India). She is also a seasoned business, creative and academic writer. She is a certified fitness instructor, personal trainer & sports nutritionist through IFA, Florida USA. Mamta is an NCFE-certified Holistic Health Therapist SAC Dip U.K. She is the lead writer and holds Expert Author status in many well-received health, fitness and nutrition sites. She runs her own popular blogs on migraines in women and holistic health. Mamta holds a double Master's Degree in Commerce and Business. She is a registered practitioner with the UN recognised Art of Living Foundation. Please visit www.mamtasingh.com

Add a CommentComments

There are no comments yet. Be the first one and get the conversation started!

Enter the characters shown in the image.
By submitting this form, you agree to EmpowHER's terms of service and privacy policy

We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.



Get Email Updates

Sunburn Guide

Have a question? We're here to help. Ask the Community.


Health Newsletter

Receive the latest and greatest in women's health and wellness from EmpowHER - for free!