Environmental
Protection Agency
National Oceanic
and Atmospheric
Administration
EPA430-F-94-017
June 1994
Experimental UV Index
ULTRAVIOLET INDEX fACTSHEET:
EXPLAMIHG THE INDEX TO THE PUBLIC
INTRODUCTION
In response to the
increasing incidence of skin
cancer, cataracts, and other
effects from exposure to the
sun's harmful rays, the
National weather Service
(NWS), the U.S. Environmental
Protection Agency (EPA), and
the centers for Disease
Control and Prevention (CDC)
are collaborating on a nev sun
awareness information program.
Central to this program
is an Experimental Ultraviolet
(UV) Index which has been
developed by the National
Meteorological center, a part
of the national Weather
Service. The EPA Office of
Research and Development
provided partial funding for
the development of -this Zndex.
The Zndex is a next-day
forecast of the likely
exposure to ultraviolet
radiation for a particular
location at noon. This summer
the NWfl will issue the Zndex
as a daily product on a
experimental pilot basis for a
limited number of cities.
"Be sun Wise!" is a
public information program
supporting the UV Zndex. Its
goal is to inform individuals
about how to use the Zndex to
prevent overexposure to the
sun for themselves and others,
•specially children.
Several publications are
being issued at the same time
as this uv Experimental Zndex
is being announced. Informa-
tion on hov to obtain these
publications is given in the
"For Additional Information"
section at the end of this
publication.
o A publication, Draft NOAA-
EPA Program to Provide
ntal Operat
Forecast Guidance of an Zndex
of UV Radiation at the Ground r
has been written for the NWS
field staff and the
professional meteorological .
community.
o A brochure. Experimental
Ultraviolet Index; What You
want to Know, is intended to
explain the Zndex to the
public. Zt is available in
quantity.
o This publication, The
Experimental Ultraviolet Zndex
Paetaheet: Explaining the
Index to the Public, provides
information about how these
Zndex values can be explained
to the public. The primary
audiences for this factsheet
are meteorologists, public
health officials, physicians,
and other professionals who
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are likely to be called upon
to answer public inquiries
about the Index or who can
make use of the Index to
increase public awareness
about the hazards of
overexposure to UV rays.
o A supplementary publication,
Technical Appendices to the
Experimental UV Index
Factsheet, provides more in-
depth information about the
Index and how EPA has
calculated the minutes to burn
associated with the different
exposure levels. The primary
audience for that publication
is professionals in the
meteorological and medical
communities who want more
technical information about
these issues.
o A separate publication,
Bulletin of Sample Public
Health Messages to Accompany
the UV index, provides a
variety of public health
action messages that can be
used when the Index values are
presented to the public.
Contents
Introduction 1
What the Index Is 2
T£e. Exposure Categories....3
Factors Affecting Individual
Exposure 3
UV Rays and Htw overexposure
Can Be Harmful 4
How People Should Use the UV
Index 6
What Role does Ozone Layer
Depletion Play 8
For Additional
Information 8
WHAT THE INDEX 18
The logo for the Experimental
UV Index from the National
weather Service and U.S.
EnviraTM|>**]tttal Protection.
Starting in the summer of
1994, the National Weather
Service (NWS) and EPA are
offering a new product, the UV
Experimental Index. It is
being issued daily on an
experimental basis for use by
meteorologists as part of
their weather report. The
index is a next day forecast
of the amount of ultraviolet
radiation that will reach the
earth's surface during the
peak hour of sunlight around
noon. The Index includes the
effects of cloud cover on the
anticipated UV exposure level
for the next day.
The Index is a number on
a scale of 0-15. The NWS
distributes this Index number
for a selected number of
cities across the country. „ It
is sent out by the NWS about
1:00 EOT each day to its field
operations and the weather
forecasting community.
Table 1 below lists five
exposure category descriptors
(e.g., minimal, low, moderate,
high, very high) that can be
used to explain the intensity
of each of the Index values.
A variety of public health
messages for each exposure
category is suggested in the
EPA publication, Bulletin of
Public Health Messaes
to Accompany the Experimental
UV index.
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Table l: index Values and Exposure Categories
INDEX VALUES
0-2
3-4
5-6
7-9
10 +
EXPOSURE CATEGORY
Minimal
Low ' ; ''• *V.
Moderate ;-•'.
High
Very High
THE EXPOSURE CATEGORIES
The exposure categories
play a key role in the sun
awareness public health
messages associated with the
Index. EPA set the exposure
categories based on sunburning
of fair-skinned persons
because it provides an easy-
to-understand measure of
immediate effects. This is a
conservative approach/ which
is meant to be protective of
people who are less likely to
sunburn but who are at risk of
the other longer-term health
effects from UV exposure that
do not depend on skin type.
Some people with skin
types will learn that they
need to take more precautions
to protect themselves from
sunburn that the exposure
descriptors would indicate;
others will realize that they
are not as sensitive, and
therefore do not have to be so
cautious.
What is important is that
people of all skin types can
use the Index to help them
prevent diseases of the skin
and eye that result from
overexposure to UV rays.
FACTORS AFFECTING INDIVIDUAL
EXPOSURE
It is important that the
public be educated on the
factors that can affect UV
radiation so that the public
make the best use of the
Index. In some cases/ the
factors that influence the
noon time UV levels may change
over the course of a day or
during a year at a given
location. These factors may
change as an individual
travels short or long
distances from where the
Index is given.
One of the most important
factors is cloud cover.
Partly or variably cloudy days
do little to reduce UV " '*'•
exposure. However/ rainy or
substantially overcast days
will reduce UV exposures — in
some cases by 50 percent or
more. Furthermore/ depending
on the accuracy of the
forecast of cloud cover at
noon and the change in cloud
cover during the day, the
forecast could overstate or
understate the actual UV
intensity at certain times
during the day.
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For example, if the •
forecast for tbe next day at
noon is for overcast skies,
but the overcast conditions
fail to occur or there are
sunny skies at other times of
the day, people may take too
fev precautions and be
overexposed. In contrast, if
clear sky conditions are
forecast but the day turns
cloudy, the UV Index would
overestimate the UV intensity
and people may not need the
precautions they had planned.
Another important factor
in determining the amount of
exposure an individual
receives is the time of day
spent in the sun. The Index
is the predicted UV exposure
for the hour around noon. The
earlier or later one goes out
in the sun, the more exposure
will be reduced. The peak
exposure time is 12:00 p.m.
Standard Time (8T) and 1:00
p.m. Daylight Savings Time
(DST). In the continental
United States, the UV
intensity is reduced by about
half at three hours before and
three hours after the peak
exposure time. For example,
the UV intensity at 10 a.m.
and 4 p.m. is hs\f ,,as strong
as it is at 1:00 p.m. DST.
The time of year also
affects the amount of UV
radiation reaching the earth's
surface. The greatest amount
of UV is received in the late
spring and early summer, much
less is received in the late
fall and early winter.
UV intensity also varies
by latitude and altitude, with
higher values occurring as one
gets closer to the equator .or
higher in elevation, smog
conditions can reduce UV
intensity.
The role of reflective
surfaces is also important in
determining the amount of
exposure. Water, sand, and
snow all reflect UV rays and
can intensify exposure.
Lifestyle decisions can
override other factors in
determining a person's risk
from exposure to the sun.
People who work or play
outdoors for long periods of
time are at greater risk of
harmful effects from UV
exposure. Activities such as
skiing, sunbathing, or
swimming can lead to extremely
high exposures. Use of
tanning parlors also increase
risk, because UV radiation
from any source contributes to
long-term damage.
UV RAYS AMD HOW 0VBRBXPOSURE
TO THEM CAH BE HARMFUL
Energy from the sun
reaches the earth as visible,
infrared, and ultraviolet
rays. Ultraviolet A is made
up of wavelengths 320 to 400
nanometers (am) in length;
ultraviolet B wavelengths are
280 to 320 nm; and ultra-
violet C wavelengths are 100
to 280 nm. Because the
earth's atmosphere absorbs the
UVC wavelengths, the only
ultraviolet rays that reach
the earth's surface are UVA
and DVB.
While a small amount of
exposure to sunlight can be
healthy and pleasurable, too
much can be dangerous. Expo-
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sure to UV rays is linked*to a
number of harmful health
effects.
other skj
Some effects of
sunlight on the skin are
visible within hours or days
(e.g., sunburn and tanning);
other effects are delayed and
cumulative and may be seen in
months to years (e.g., skin
cancer and photoaging).
skin cancer. The
incidence of skin cancer eases
is increasing rapidly, over
1,000,000 new cases of skin
cancer are likely to be
diagnosed in the U.S. this
year. Eighty percent of the
UV exposure occurs before the
age of 18 and the damage is
cumulative over time. UV
radiation exposure is
implicated in the formation of
non-melanoma and melanoma
cancers.
Premature aaino. Sun
exposure also causes premature
aging of the skin. Photoaging
of the skin is different than
normal chronological aging.
Regular sun bathers show
photoaging changes early in
life (before 30 years of age);
while chronologically aged
skin shows changes later
(after 40 or more years of
age). Freckling, fine
wrinkling, and dilatation of
capillaries are often seen
early in the photoaging
process; later on the
photoaged skin develops
irregular pigmentation, often
called liver spots. Both
photoaging and chronological
aging cause wrinkling and loss
of skin elasticity; however,
they occur much earlier when
the skin has been overexposed
to the sun.
Cataracts and other eye
disorders, cataracts are a
leading cause of blindness
worldwide. UV exposure is one
of the risk factors in the
development of cataracts.
Corneal sunburn, growths on
the outer surface of the eye,
and other eye diseases, are
also known or suspected to be
related to long-term exposure
to UV radiation.
Tmnune
maae. The
skin is part of the body's
natural defense system. While
there is much to be learned,
it is clear that ultraviolet
radiation can alter immune
functions. When UV radiation
suppresses immune responses,
it reduces the body's ability
to fight off certain diseases,
including skin cancer.
Overexposure to UV radiation
may also interfere with the
efficacy of immunisations
administered through the skin.
UVB rays pose a much
greater risk of skin cancer
than UVA. However, UVA rays
cause aging, wrinkling, loss
of elasticity, and augment the
damaging effects of UVB,
including skin cancer.and
cataracts. The five exposure
categories include exposure to
both UVA and UVB.
Common sense measures to
prevent overexposure to
sunlight can substantially
reduce the risks of cancers
and aging of the skin,
cataracts, and other harmful
effects.
U
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HOW PEOPLE SHOULD USE THE 47V
XBDEX
EPA is collaborating with
CDC is the initiation of a "Be
Sun ise!" public education
campaign to coincide with the
release of the Index. This
campaign is aimed at raising
public awareness of the health
risks of sun exposure. The
challenge is great because
attitudes about the
attractiveness of a "healthy
tan1' are so firmly
established.
Preventing skin cancer and
other skin damage.
Because individual
susceptibility to sunburn
varies widely, each individual
should determine his or her
own skin type. Refer to
"Table 2: Description of Skin
Phototypes" below.
The first step in
classifying an individual's
skin type is to look at the
color of skin on parts of the
body that have received the
least amount of exposure to
the sun. Lower legs just
above the ankles, behind the
knee, or the inner side of the
upper arm are possible places
to use. People should not use
the exposed skin on the face,
neck, or arms (or chest for
men) because the color in
these areas has been altered
by past sun exposure.
Other factors including
genetic history, age, number
of previous severe sunburns,
and medical history are also
important. Individual
determinations about skin type
should be made after careful
consideration of all these
influences. Hasty self-typing
can result in actions which
lead to overexposure to the
sun.
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Table 2: Description of Skin Phototypes
SKIN PHOTOTYPES
SKIM COLOR IN
UNEXPOSED AREA
TANNING HISTORY
Never Tans/
Alvays Burns
pale or milky white;
alabaster
develops red sunburn;
painful swelling;
skin peels
Sometimes Tans/
Usually Burns
very light brown;
sometimes freckles
usually burns;
pinkish or red
coloring appears; can
gradually develop
light brown tan
Usually Tans/
Sometimes Burns
light tan, brown, or
olive; distinctly
pigmented
infrequently burns;
shows moderately
rapid tanning
response
Always Tans/
Rarely Burns
brown, dark brown,
or black
rarely burns; shows
very rapid tanning
response
Even within the same skin
type, people may burn at
different rates. Individuals
should decide if they are more
or less sensitive to sun
exposure and take protective
actions accordingly.
The American Academy of
Dermatology and the Skin
Cancer Foundation recommend
the following actions to
reduce the chance of both
sunburn and skin cancer:
o Minimize sun exposure at
midday (10:00 a.m. to 3:00
p.m.)
o Apply a sunscreen with SPF-
15 or higher to all exposed
areas of the body.
o Reapply sunscreen every two
hours, even on cloudy days.
Also, reapply after swimming
or perspiring.
o Wear clothing that covers
the body and shades the face.
o Avoid unnecessary exposure
to radiation through sunlamps
or tanning parlors.
o Protect children by keeping
them from excessive sun during
the hours of strongest
sunlight and by applying
sunscreen liberally and
frequently to children older
than 6 months of age.
(Because sunscreen should not
be used on children under 6
months, their sun exposure
should be severely limited.)
Preventing cataracts and other
eve diseases.
Unlike individual
susceptibility to sunburn and
cancer, susceptibility to eye
damage from uv may well be
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similar for all types of »
people.
The National Society to
Prevent Blindness, the
American Optometric
Association, and the American
Academy of Ophthalmology
recommend the following
actions to prevent eye damage
from DV radiation:
o Wear sunglasses consistently
when outside during the
sunlight hours. Wearing
regular glasses also affords
some measure of protection
against UV rays.
o Wear broad-brimmed hats to
shade the eyes. (Hats that
shade the back of the .neck
also protect the skin.)
Choose sunglasses
carefully. Sunglasses should
absorb 99-100 percent of the
full UV spectrum. Because
there is now no uniform
labeling of sunglasses, people
should read labels carefully
to be sure that the lenses
will absorb both UVA and DVB
light. They should be wary of
claims that sunglasses "block
harmful UV light" without
saying how much and claims of
"protection", instead of
"blockage" or "absorption."
WHAT ROLE DOBS OZONE LAYER
DEPLETION PLAT?
The stratospheric ozone
layer shields the earth
from the sun's harmful
ultraviolet rays. It is well
established that decreases in
the stratospheric ozone far
above us can lead to increases
in UV at the surface. Ozone
changes from day to day and
place to place.
Long-term decreases in
the average amount of ozone
have been measured over the
past decade. A better
monitoring network is
necessary to demonstrate
whether there has been a
corresponding change in UV
radiation in the United
States. Future levels of
ozone and UV will depend upon
a combination of natural and
manmade factors, including
CFCs.
Experts agree that
increased exposure to harmful
rays can contribute to long
term increases in skin cancer
and cataracts, and harm
animals and plants. It is
likely that current rising
rates of skin cancer are
related to the increasing
emphasis on outdoor leisure
and work in our society.
Whatever the source of risk,
it is important to protect
yourself and your family from
overexposure to harmful UV
rays.
FOR ADDITIONS, TNFORMATION
ORGANIZATIONS
Federal Agencies
The following federal
agencies have information on
the uv index or related
issues, including skin cancer
and ozone depletion. Public
inquiry telephone numbers are
provided where available.
8
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NOAA/National Weather Service
Katio&al Meteorological Center
Washington, DC 20233
301-713-0622
(for information on
Experimental UV index)
Be Sun Wise! Program
U.S. EPA
401 M Street 8W (6205J)
Washington DC 20460
(for information on index and
health messages)
EPA stratospheric ozone
Information Hotline
1-800-296-1996
Centers for Disease Control
and Prevention
National Center for Chronic
Disease Prevention and
Health Promotion
Division of Cancer Prevention
and Control
4770 Buford Highway HE,
Mailstop K-57
Atlanta, GA 30341-3724
(for information on public
education about skin cancer)
Cancer Information Service
National cancer Institute
1-800-4-CANCER
(for information on skin
cancer)
Private Sector
American Academy of
Dermatology
930 North Meacham Road
P.O. BOX 681069
schaumburg, IL 60168-4014
American Academy of .
Ophthalmology
Public Inquiries Unit
P.O. Box 7424
San Francisco, CA 94120-7424
American Cancer Society
1-800-ACS-2345
American Optometric
Association
243 N. Lindbergh Blvd
St. LOUis, MO 63141
Skin Cancer Foundation
245 Fifth Avenue
New York, NY 10016
212-725-5176
Prevent Blindness America
500 East Remington Road
Schaumberg, IL 60173-5611
1-800-331-2020
In addition, you may also
find helpful information by
calling or writing health care
providers in your own
community, including local
medical societies. Also talk
with your own personal
physician
PUBLICATIONS
Brochures
The following brochures
or flyers provide information
on the Index and related
issues, see above for
addresses (and public inquiry
telephone numbers where
available).
American Academy of
Dermatology. Melanoma/Skin
Cancer. 1993.
American Association of
ophthalmology. Sunglasses.
1993.
American Association of
Ophthalmology. The Ocular
Hazards of UV Exposure. 1993.
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EPA, NWS, CDC (in -
collaboration with many other
organisations) . Experimental
Ultraviolet Index; What You
Want to Know. 1994.
EPA. Technical Appendices to
the Experimental uv Index
Fact sheet. 1994.
EPA. Bulletin
n»«pie Health
Messages to Accompany the
Experimental UV Index. 1994.
EPA* Experimental UV index Qa
t As for Meteorologists. 1994.
EPA. Protecting the Ozone
Layers A Citizen's Checklist.
1994.
National Cancer Institute/NIH.
What You Need to Know About
Skin Cancer. 1992.
KW8. Draft NORA— EPA Program to
Provide Experimental
operational Forecast Guidance
of an Index of UV Radiation at
the Ground. 1994.
Prevent Blindness America.
UV; A Hazard to Sight. 1994.
Other Books andReferences
Robins, Perry, sunsense: A
Complete Guide to Prevention.
Early Detection. Treatment of
Skin Cancer. The Skin Cancer
Foundation. 1990. :
Tilton, Buck and Roger Cox.
Ozone* UV and Your Healths SO
Wavs to Save Your Skin. IC8
Books, Inc. Merrillville,
Indiana. 1994.
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