United States
Environmental Protection
Agency
A GUIDE TO THE
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The UV Index is Changing.
The Ultraviolet (UV) Index, developed in 1994
by the National Weather Service (NWS) and the
U.S. Environmental Protection Agency (EPA),
helps Americans plan outdoor activities to avoid
n-vvvK4
overexposure to UV radiation and thereby lower
their risk of adverse
health effects. UV radia-
tion exposure is a risk
factor for skin cancer,
cataracts, and other ill-
nesses. The incidence of
skin cancer, including
melanoma, has increased
significantly in the United
States since the early
1970s.
MELANOMA INCIDENCE IN THE UNITED STATES
(per 100,000 people)
Source: National Cancer Institute
SEER Program 16.3
12.7
8.7
L
The UV Index is a useful tool to help the general public take steps to
reduce their exposure to solar UV radiation, but its effectiveness depends
on how well the information is communicated to the
public. This brochure provides important information on
new reporting guidelines for solar ultraviolet radiation.
It is intended to assist communicators in several
fields meteorology, public health, education, and the news media
in conveying UV information to the public. Professionals in these fields
are uniquely positioned to raise awareness of how to prevent skin cancer.
Beginning in May 2004, EPA and NWS will report the UV Index consistent
with guidelines recommended jointly in 2002 by the World Health
Organization (WHO), the World Meteorological Organization, the United
Nations Environment Programme, and the International Commission on
Non-Ionizing Radiation Protection. These organizations recommended a
Global Solar UV Index in order to bring worldwide consistency to UV reporting
and public health messaging.
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The UV Index informs the public of the level
of UV exposure expected on a given day. It is
reported as a prediction of the UV level at
noon, although the actual UV level rises and
falls as the day progresses.
What's New About the
UV Index?
UV Index Variation During a Summer Day
St. Louis, Missouri, June 20,2Bu3
4AM
SAM 11AM 1PM 4PM
TIME OF DAY
8PM
UV Index
Prior to May 2004
The New
Global Solar UV Index
Exposure
Category
MINIMAL
LOW
MODERATE
HIGH
VERY HIGH
Index
Number
0-2
3-4
5-6
7-9
10+
Exposure
Category
LOW
MODERATE
Index
Number
3-5
The UV I ndex was previously reported on
a scale of 0 to 10+, with 0 representing
"Minimal" and 10+ representing
"Very High." As of May 2004, EPA and
NWS will report the Global Solar UV
Index using a scale of 1 (or "Low")
to 11 and higher (or "Extreme").
Additional differences include a new
color scheme, revised exposure
categories, and different breakpoints
between exposure categories.
Although the categories have been
reorganized and labeled, actual
UV levels associated with the exposure
categories in the Global Solar UV
Index have not changed. In other words,
a UV index report of 6 represents the
same intensity UV radiation on both
the old and new scales, even if 6 is
called "Moderate" on the old scale
and "High" on the new scale.
Consistent reporting of the index will help the public better understand
UV risk. We therefore strongly urge providers of the UV Index to
adopt the new scale and color scheme. The color scheme ranges
from green (for "Low") to violet (for "Extreme").
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The UV Index reminds people to protect themselves when engaging in their
normal outdoor activities. UV radiation exposure poses varying degrees of
risk for all people because it affects eyes and skin. People with sensitive skin
should always take action to protect themselves. It is especially important
that parents and caregivers know how to protect babies and young children
who are more susceptible to overexposure.
EPA recommends that communicators
always encourage individuals to
understand and practice the following
sun protection steps:
Check the UV Index for the UV forecast.
Limit exposure during midday hours.
Seek shade.
Wear clothing made from tightly
woven fabrics. UV rays can pass
through holes and spaces in loosely
knit fabric. Long-sleeved shirts and
pants are recommended.
Wear a hat with a wide brim that
protects the eyes, face, and neck.
Wear sunglasses that provide 100%
UV protection.
Use broad spectrum sunscreens with
at least Sun Protection Factor (SPF)
15 and reapply regularly. Remember
to apply sunscreen on any part of the
skin that is exposed to the sun, such
as the nose, the back of the neck, and
the rims of the ears. Use lip balms or
creams containing sunscreen.
Communicating
the UV Index
When used correctly, shade, clothing, and hats provide the best protection from
UV radiation. While sunscreen is effective when applied properly, doctors caution
that sunscreen should not be used to prolong the duration of sun exposure.
Sun Protection Messages
When reporting or discussing the UV Index, it might be helpful to give your audience
more information about the significance of the reported UV Index for a given day
by suggesting simple actions they can take to avoid overexposure. For this reason,
EPA recommends that you use some of the messages identified in the chart below
when reporting the UV Index. The Myths and Realities About Fun in the Sun on
page 6 of this brochure may also be useful as "health tips."
Exposure
Category
LOW
MODERATE
J H,CH )
VERY HIGH
EXTREME
Index
Number
1-2
3-5
6-7
8-10
11+
Sun Protection Messages
Wear sunglasses on bright days. In winter, reflection off snow can nearly double UV strength.
If you burn easily, cover up and use sunscreen.
Take precautions, such as covering up and using sunscreen, if you will be outside.
Stay in shade near midday when the sun is strongest.
Protection against sunburn is needed.
Reduce time in the sun between 11 a.m. and 4p.m.
Cover up, wear a hat and sunglasses, and use sunscreen.
Take extra precautions. Unprotected skin will be damaged and can burn quickly.
Try to avoid the sun between 11 a.m. and 4 p.m. Otherwise, seek shade, cover up, wear a hat and
sunglasses, and use sunscreen.
Take all precautions. Unprotected skin can burn in minutes. Beachgoers should know that white sand
and other bright surfaces reflect UV and will increase UV exposure.
Avoid the sun between 11 a.m. and 4 p.m.
Seek shade, cover up, wear a hat and sunglasses, and use sunscreen.
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Variations in the UV Index
The intensity of the sun's
UV rays reaching the earth's
surface, and the UV Index
ratings, vary according to
many factors. All influence
the UV Index in locations
across the U.S.
CLOUD COVER, if heavy, can block
most UV radiation. Thin or broken
clouds allow most UV rays through.
Puffy, fair-weather clouds deflect
rays and can increase UV radiation
reaching the surface.
OZONE absorbs UV radiation.
The higher the amount of ozone,
the fewer rays reach the surface.
Ozone levels vary from day to day
and throughout the year.
ALTITUDE affects UV radiation;
UV increases about 2% for every
1,000-foot increase in elevation
due to thinner mountain air.
TIME OF DAY affects UV radiation,
which peaks at midday (with the sun
highest in the sky), and lessens in the
early morning and late afternoon.
LAND COVER, such as
structures and trees,
significantly reduces exposure
to UV radiation
SEASONS affect UV
radiation, which peaks
in spring and summer
(April to August),
declines in fall, and is
lowest in winter.
EARTH SURFACE CHARACTERISTICS
can reflect or scatter UV radiation.
Snow may reflect as much as 80% of
UV, sand 15%, and water 10%.
LATITUDE affects UV radiation,
which is strongest at the equator and
declines toward the poles.
HOW THE UV INDEX IS CALCULATED
The UV Index represents the amount of skin-damaging UV
radiation reaching the earth's surface at any instant of time.
The basic UV Index forecast is given for solar noon the
sun's highest point in the sky and the time of the highest
fluctuation in UV radiation (under clear sky conditions).
A UV Index forecast begins with a forecast of the total ozone
amount. All the forecast parameters used in the UV Index
computation are derived from NWS forecast models. The sun
angle at solar noon (or for any other time) for that day is
determined. A radiative transfer model determines the flux of
UV radiation for a range of wavelengths. An action spectrum
weights the response of the human skin to UV radiation at
each wavelength. Once weighted, the flux values are integrated
over the entire range, resulting in an erythemal dose rate
the instantaneous amount of skin-damaging radiation reaching
the surface under clear sky, at sea level, with low aerosol
conditions, as measured by units of milliwatts per square
meter. Adjustments then account for a location's elevation,
aerosol, and cloud conditions. Next, the optical properties
of cloud conditions expected at that time refine the dose
rate further. Finally, the resultant dose rate is applied to the
UV Index. One UV Index unit is equivalent to 25 milliwatts
per square meter.
Different areas of the country have different degrees of variation
in the UV Index from day to day and from season to season.
Communicators should consider how best to report the UV Index
value to their audience so that people actually put recommendations
into practice and use the UV Index as a guide to healthy behavior.
If UV levels in your area tend to be unchanging particularly if
they are consistently high during summer months EPA suggests
that you emphasize general sun protection steps (for example,
reminding people to wear sunglasses with 100% UVA & UVB
protection); make note of local factors that can affect daily UV
levels; and encourage special protection for children.
AVERAGE UV INDEX VALUE
Winter Summer
Atlanta, Georgia
Phoenix, Arizona
Anchorage, Alaska
Honolulu, Hawaii
New York, New York
Portland, Oregon
St. Louis, Missouri
Miami, Florida
2 (Low)
3 (Moderate)
<1 (Low)
6 (High)
1 to 2 (Low)
1 (Low)
1 to 2 (Low)
4 (Moderate)
8 (Very High)
10 (Very High)
3 to 4 (Moderate)
11 to 12 (Extreme)
6 to 7 (High)
5 to 6 (Moderate-High)
7 to 8 (High-Very High)
10-11 (Very High-Extreme)
Typical UVI values for different parts of the U.S. at midday. These values
may vary significantly depending on cloud cover and ozone levels.
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Overexposure to the suns ultraviolet rays is the most
important preventable factor in the development of
skin cancer. Skin cancer is largely preventable when
sun protection measures against
UV rays are used consistently. \\slC
However, many young people
and adults do not consistently s^r^sJ ^i i
use sun protection measures Cll IU U
and are unaware of the link
between overexposure and
health risks.
UV Radiation
and Public Health
Reporting Burn Times Not Recomm
Communicators sometimes report
"time to burn" in lieu of the UV
Index level, as a simple concept that
can easily be translated into action.
However, people can interpret burn
times as a safe period during which
they do not have to take protective
action. Relating UV Index values to
"time to burn" or "safe tanning time"
sends an incorrect and potentially
harmful message to the general
public. The UV Index should not be
used to suggest that unprotected
exposure is risk-free.
es About Fun in the Sun
A suntan is healthy.
Establishing a base suntan
protects you from sun damage.
You cannot get a sunburn on
a cloudy day.
UV radiation during winter
is not a concern.
A tan results from the body defending itself
against further damage from UV radiation.
Any change in your skin's natural color is
a sign of damage to the skin.
Sunburn is possible on a cloudy day. Up
to 80% of solar UV radiation can penetrate
light cloud cover.
UV radiation is generally lower in winter,
but snow reflection can double overall
exposure especially at high altitudes
leading to sunburn and snowblindness.
Sunscreen protects you so that
you can sunbathe much longer.
Sunscreen should not be used to increase
sun exposure time but to increase
protection during unavoidable exposure.
If you take breaks while
sunbathing, you won't get
sunburn.
UV radiation exposure is cumulative during
the day.
If you don't feel the sun's hot
rays, you won't get sunburn.
Skin cancer only occurs on
parts of the body that are
exposed to the sun all the time.
Sunburn is caused by UV rays that cannot
be felt. The heating effect is caused by the
sun's infrared radiation and not by UV.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^H
Melanoma occurs most commonly on the
back (for men) and legs (for women), which
are sites with only intermittent exposure.
Skin cancer only happens to
people who are very fair-skinned.
§
Skin cancer commonly occurs in people
who tan before they burn.
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'ISK FACTORS
Everybody, regardless of race or ethnicity, is subject to the adverse effects
of overexposure to the sun. Some people might be more vulnerable to certain
conditions, however.
Skin type affects the degree to which some people burn and the time it
takes them to burn. The Food and Drug Administration (FDA) classifies skin
type on a scale from 1 to 6. Individuals with lower-number skin types (1
and 2) have fair skin and tend to burn rapidly and more severely. Individuals
with higher-number skin types (5 and 6), although capable of burning, have
darker skin and do not burn as easily.
The same individuals who are most likely to burn are also most vulnerable to
skin cancer. Studies have shown that individuals with large numbers of freckles
and moles have a higher risk of developing skin cancer. Although individuals
with darker skin types are less likely to develop skin cancer, they should still
take action to protect their skin and eyes from overexposure to the sun.
SKIN CANCER
UV radiation causes genetic mutations
in skin cells. Over time, such mutations
due to exposure to the sun and severe
sunburns can lead to skin cancer. Every
year, more than one million Americans
are diagnosed with skin cancer, making
it the most common form of cancer in
the country. In the United States, one
person dies of skin cancer every hour.
The most common places for skin
cancer to develop are on those body
parts exposed to the sun, such as the
face, neck, ears, forearms, and hands.
The three main types of skin cancer
are basal cell carcinoma, squamous
cell carcinoma, and melanoma.
Basal carcinomas are tumors that
usually appear as small, fleshy bumps
or nodules.
Squamous cell carcinomas appear as
nodules or as red, scaly patches.
Melanomas may appear without
warning as a dark mole or other dark
spot in the skin. Melanoma causes
more than 75% of skin cancer deaths.
There are more than 50,000 new
cases of melanoma per year. One in
four persons who develop melanoma
is under 40.
All three types of skin cancer may be
successfully treated if detected in their
early stages. Fa more information about how
to detect skin cancer, visit the Center for
Disease Control's skin cancer website at
http://www.cdc.gov/cancer/nscpep/index.htm.
SUNBURN
The most obvious result of too much
UV exposure is sunburn, which
involves skin redness and sometimes
tenderness, swelling, blistering, fever,
and nausea. However, tanned skin
also poses a skin cancer risk.
SUN SENSITIVITY
Some people may develop bumps,
hives, blisters, or red blotchy areas as
an allergic reaction to sun exposure.
Certain drugs, perfumes, and cosmetics
also may make some people sensitive
to the sun.
EYE DAMAGE
Excess exposure to UV radiation can
cause a painful burn of the cornea.
Chronic eye exposure to UV radiation
may also increase the incidence of
cataract, which is a clouding of the
eye lens; pterygium, in which a flesh
membrane covers the eye; and
possibly macular degeneration, or the
development of spots that could result
in blindness. About 13 million Americans
age 40 or older have cataracts, and
more than half of all Americans 65 or
older have some evidence of cataracts.
PREMATURE WRINKLING
In the long run, too much exposure to
the sun may change the skin's texture,
giving it a tough, leathery appearance.
Up to 90 percent of the visible skin
changes commonly attributed to aging
are caused by sun exposure. The sun
also may cause discolorations in skin
tone including red, yellow, gray, or
brown spots.
IMMUNE SYSTEM SUPPRESSION
AND DISEASE
Sun exposure suppresses the immune
system and may make the body more
vulnerable to infections and cancers,
regardless of an individual's skin type
or susceptibility to burns.
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FOR MORE INFORMATION
Additional sun safety information from EPA's SunWise Program is available by calling the National Service Center
for Environmental Publications at 1-800-490-9198.
The Environmental Protection Agency offers a free SunWise Kit to meteorologists. The kit provides fun and interactive
ways to teach kids about UV science and sun safety. Information is available at http://www.epa.gov/sunwise.
EPA also offers next-day UV Index forecasts by ZIP code for the continental United States, contoured UVI maps,
and additional UVI information at http://www.epa.gov/sunwise/uvindex.html.
The National Weather Service provides UVI forecasts for 58 cities, UVI climatologies, and additional information
at http://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/index.html.
The World Health Organization's INTERSUN program has developed a graphics package, including a UVI logo, an
international color code for different UVI values, and a choice of ready-made graphics for reporting the UVI and
sun safety messages. The materials may be downloaded and used free of charge. An overview of these graphics
is available at http://www.who.int/entity/uv/publications/en/UVIclip.pdf. GIF images may be downloaded at
http://www.who.int/docstore/peh-uv/UVIndex_Graphics/gif. To request a CD-ROM containing formats other than
GIF, please contact UVinfo@who.int.
United States
Environmental Protection
Agency
Air and Radiation
(6205J)
EPA430-F-04-020
May 2004
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