Health Consequences of Excessive Solar UV Radiation

Health Consequences of Excessive Solar UV Radiation

July 26, 2006

New WHO Report Shows Breakdown of Disease Caused by UV Radiation

    GENEVA, July 26 /Xinhua-PRNewswire/ -- Ultraviolet
radiation from the sun causes a considerable global disease
burden, including specific cancers, a new World Health
Organization (WHO) report finds.  Much of the UV-related
illness and death can be avoided through a series of simple
prevention measures. 

    (Logo: 
http://www.newscom.com/cgi-bin/prnh/20040610/CNTH001LOGO )

    The report, Global Burden of Disease of Solar
Ultraviolet Radiation estimates that up to 60,000 deaths a
year worldwide are caused by too much exposure to
ultraviolet radiation (UVR).  Of those 60,000 deaths, an
estimated 48,000 are caused by malignant melanomas, and
12,000 by skin carcinomas.

    In total, more than 1.5 million DALYS
("disability-adjusted life years") -- a measure
of the loss of full functioning due to disease and death
are lost every year due to excessive UVR exposure.  The
most serious consequence of excess UVR is malignant
melanoma, which has high cure rates only if detected early.
 Up to 90% of the global burden of disease from melanoma and
other skin cancers are estimated to be due to UVR exposure.

    The new WHO report is the first-ever systematic
examination of the global health burden due to UVR.  It
investigates nine adverse health outcomes from excess UVR
exposure.  The main three, which cause the greatest burden
of disease from UVR, are cutaneous malignant melanomas, and
non-melanoma skin cancers developing in different cell
layers of the skin (squamous cell carcinomas and basal cell
carcinomas).  In addition, UVR causes sunburn, skin
photoageing, cortical cataracts (eye lens opacities),
pterygium (a fleshy growth on the surface of the eye),
reactivation of herpes of the lip (cold sores) and the rare
squamous cell carcinomas of the eye.

    "This global assessment of the health risks of UV
radiation provides a good basis for public health action. 
We all need some sun, but too much sun can be dangerous --
and even deadly.  Fortunately, diseases from UV such as
malignant melanomas, other skin cancers and cataracts are
almost entirely preventable through simple protective
measures," said Dr Maria Neira, Director for Public
Health and the Environment at WHO.

    The report notes that UVR does have beneficial effects,
mainly in the production of vitamin D following skin
exposure to the UVB (shorter wavelength) component of UVR. 
Adequate vitamin D prevents the development of bone diseases
such as rickets, osteomalacia and osteoporosis.  Moreover,
the possible beneficial effects on some cancers and immune
disorders are under investigation.

    WHO notes, in most cases minimal casual exposure to UVR
should be sufficient to maintain vitamin D levels at a range
that avoids these health problems.  The dangers are much
greater from over-exposure to the sun's radiation.

    A few easy-to-implement sun safety measures could
prevent much of the cancer and other death and disease
burden due to UV radiation, WHO says:

     -- Limit time in the midday sun
     -- Use shade wisely: seek shade when UV rays are most
intense
     -- Wear protective clothing including hats and
sunglasses
     -- Use a broad-spectrum sunscreen of sun protection
factor 15+
     -- Avoid sunlamps and tanning parlours; for youth
under the age of 18, 
        WHO recommends that they do not use them at all
     -- Know the UV index: when the UV Index predicts
radiation levels of 3 
        (moderate) or above
     -- sun safety practices should be taken
     -- Protect children from the sun

    More information on these measures can be found at
http://www.who.int/uv .

    In conjunction with the launch of this new report, WHO
and the World Tourism Organization of the United Nations
(UNWTO) are joining forces to multiply global outreach
efforts to inform the public and reinforce measures to
prevent avoidable diseases.  Through the UNWTO, WHO will be
distributing information, including its new UV flyer on
healthy sun habits, to all national ministries responsible
for tourism.

    The report and executive summary -- Solar ultraviolet
radiation: Global burden of disease can be found on
http://www.who.int/uv/en/ .

    For more information, please contact:

     Ms Nada Osseiran, 
     Communications and Advocacy Officer, 
     Department for Public Health and Environment, 
     World Health Organization, Geneva
     Tel:   [phone]
     Fax:   [phone]
     Email: [e-mail]

    All press releases, fact sheets and other WHO media
material may be found at http://www.who.int .

    Fact Sheet 
     July 2006

    Global disease burden from solar ultraviolet radiation

    Introduction

    Everyone is exposed to ultraviolet radiation (UVR) from
the sun.  Small amounts of UV radiation are beneficial to
health, and play an essential role in the production of
vitamin D.  However, overexposure to UV radiation is
associated with a variety of health problems, most notably
skin cancer and eye cataracts.  WHO has recently assessed
the global disease burden that can be attributed to solar
UV radiation.  This information provides an important basis
for national and international UV public health and health
protection programmes to assist people to avoid
inappropriate sun exposure.

    UV Radiation

    UVR reaching the earth's surface is largely composed of
long-wavelength UVA with a small amount of the shorter
wavelength UVB.  Most UVB and the very short wavelength UVC
is filtered out by the atmosphere.  UV radiation levels are
influenced by:

    -- Sun elevation: the higher the sun in the sky, the
higher the UVR 
       level, with an increase in UVB relative to UVA. 
Thus UVR levels 
       vary with time of day and time of year.

    -- Latitude: the closer to equatorial regions, the
higher the UVR 
       levels.

    -- Cloud cover: UVR levels are highest under cloudless
skies.  However, 
       even with cloud cover, UVR levels can be high due to
scattering 
       within the atmosphere. 

    -- Altitude: at higher altitudes, the atmosphere is
thinner and the air 
       mass is decreased; less UVR is absorbed.

    -- Ozone: ozone present in the atmosphere absorbs some
of the UVR that 
       would otherwise reach the earth's surface.  Ozone
depletion leads to 
       increased UVB levels with little impact on UVA
levels.
 
    -- Ground reflection: grass, soil and water reflect
less than 10% of 
       UVR; fresh snow reflects as much as 80%; dry beach
sand about 15% 
       and sea foam about 25%. 

    UVR can neither be seen nor felt.  Therefore UVR
measurements are necessary to determine precisely the
extent of ground level (ambient) UVR. UVR measurements such
as the global solar UV index (see http://www.who.int/uv )
add up all the solar UVR, taking account of its ability to
cause skin damage.  If measurements are not available, an
approximation of ambient UVR levels can be based on
geographic latitude. 

    For individuals, the UVR exposure additionally depends
on factors such as behaviour and use of sun protectants,
e.g., clothing, hats, sunscreen and sunglasses, during
outdoor (including occupational) activities. A person's
skin type is also important.  Fair skinned people suffer
from sunburn much more readily than dark-skinned people. 

    Health consequences of excessive UVR exposure 

    Using evidence systematically collected from the
scientific literature, WHO has identified nine adverse
health outcomes that are clearly caused by UVR exposure. 
An assessment of the global disease burden, comprising both
mortality and morbidity, was completed for these health
outcomes. The nine diseases assessed were:

    -- Cutaneous malignant melanoma (CMM): Melanoma of the
skin is a 
       malignant cancer of great severity.  Although
treatment is improving, 
       melanoma still carries a significant risk of death. 
Between 50% and 
       90% of the burden of disease from melanoma estimated
in the WHO 
       report is due to UVR exposure.

    -- Squamous cell carcinoma of the skin (SCC): This is
another type of 
       malignant skin cancer which generally progresses
less rapidly than 
       melanoma and is less likely to cause death or
ongoing disability.  
       Of the total SCC disease burden, 50-70% is
attributable to UVR 
       exposure. 

    -- Basal cell carcinoma of the skin (BCC): This skin
cancer appears 
       predominantly in older people and grows slowly by
local spread.  The 
       incidence and mortality of BCC were estimated to be
50-90% 
       attributable to UVR exposure.

    -- Squamous cell carcinoma of the cornea or conjunctiva
(SCCC): This is 
       a rare tumour of the surface of the eye.  Some
50-70% of the disease 
       burden due to SCCC is attributable to UVR exposure.

    The following conditions are also the consequence of
excess UVR, but there is considerable uncertainty about the
overall burden of disease estimates, since few data are
available on incidence and/or UV-attributable fraction: 

    -- Photoageing: Chronic sun damage is associated with
the development 
       of skin conditions called solar keratoses.  On rare
occasions, these 
       are pre-malignant conditions.  The burden of disease
due to solar 
       keratoses is 100% attributable to UVR exposure. 

    -- Sunburn: Sunburns may be severe and blistering, and
the resulting 
       disease burden is 100% attributable to UVR exposure.


    -- Cortical cataract: Cataract is an eye disease where
the lens becomes 
       increasingly opaque, resulting in impaired vision
and eventual 
       blindness.  Long-term sun exposure to the eye
increases the risk of 
       developing a specific cataract type called cortical
cataract.  Five 
       percent of all cataract-related disease burden is
directly 
       attributable to UVR exposure.

    -- Pterygium: This is a wing-shaped fleshy growth on
the surface of the 
       eye.  40-70% of the disease burden is attributable
to UVR exposure.

    -- Reactivation of herpes of the lip (RHL): Excessive
UVR exposure 
       causes immunosuppression and reactivation of the
herpes simplex 
       virus ("cold sores").  25-50% of the
disease burden is attributable 
       to UV exposure.

    Estimates of global UV disease burden

    WHO uses disability adjusted life years (DALYs) to
measure the health detriment associated with a particular
health outcome.  DALYs combine the life years lost due to
premature mortality associated with the disease and the
number of years lost due to disability.  Thus, one DALY is
equivalent to one lost year of life in full health.

    The following table summarizes the DALYs and mortality
attributable to excessive UVR exposure for the nine
diseases listed above and calculated for the year 2000. 
The upper and lower estimates indicate the variation that
depends on actual assumptions and values used in the
calculations. Globally, around 1.5 million DALYs (0.1% of
the total global burden of disease) are lost every year due
to excessive UVR exposure.  The estimates concerning sunburn
and reactivation of the Herpes Simplex virus (cold sores)
are regarded as particularly uncertain.  Therefore summary
DALY estimates are also presented excluding these health
problems.

                                               DALYs (000)
                             
    Disease                      Upper      Lower     
Upper       Lower    
                                estimate   estimate 
estimate     estimate 
    CMM                            621        345    
58,645       32,581 
    SCC of skin                     83         59     
9,474        6,767 
    BCC of skin                     52         29     
2,921        1,623 
    Solar keratoses                  8          8         
0            0   
    Sunburn                        294        294         
0            0   
    Cortical cataract              529        529         
0            0   
    Pterygium                       35         20         
0            0   
    SCCC                             2          1         
0            0   
    RHL                             68         34         
0            0   
    Total                        1,692      1,319    
71,039       40,970 
    Total (excluding sunburn     
     and RHL)                    1,330        991    
71,039       40,970                                        
 


    In terms of mortality, only the three skin cancers
contribute to deaths that can be attributable to excessive
UVR exposure.  Between 41,000 and 71,000 deaths, with a
best estimate of around 60,000 were attributed to excessive
UVR exposure in 2000. 

    Regional differences

    The main health effects contributing to the UVR-related
disease burden differ by region:

    In the WHO European region, with a predominantly
fair-skinned population, melanoma is by far the largest
cause of UVR-attributable disease burden. Similar results
are found in some countries of the WHO Western Pacific
region, notably Australia, Brunei, Japan, New Zealand and
Singapore.  In most of the Americas, melanoma represents
the greatest UVR-attributable disease burden, but sunburn
also contributes significantly. 

    In the WHO African Region, the main burden of disease
attributable to UVR is cataract.  Even though cutaneous
malignant melanoma is uncommon in deeply pigmented
populations, it accounts for the second greatest burden of
disease in this region. 

    Cataract also causes the greatest UVR-associated
disease burden in some countries of the WHO American region
such as Bolivia, Ecuador, Guatemala, Haiti, Nicaragua, and
Peru and in the Eastern Mediterranean Region notably in
Egypt, Saudi Arabia, Iran and Iraq.  Similarly, in WHO
South East Asia Region, in countries like Indonesia,
Thailand, India, and Bangladesh, cataract is the most
important cause of disease.  In several Western Pacific
countries including China, Malaysia and the Philippines,
sunburn and cataract are the leading UV-related ill health
effects, followed by melanoma. 

    Beneficial effects of UVR exposure

    UVR exposure has beneficial effects, mainly in the
production of vitamin D. Adequate vitamin D prevents the
development of bone diseases such as rickets, osteomalacia
and osteoporosis.  Possible beneficial effects on some
cancers and immune disorders are under intense scientific
investigation.  Populations living at low latitudes (who
have not evolved a diet high in vitamin D) and deeply
pigmented populations particularly rely on UVR to produce
adequate Vitamin D levels.

    For the purpose of a theoretical assessment of the
effect of lack of UV, WHO has conducted model calculations.
 If zero exposure to UV leading to widespread and profound
Vitamin D deficiency were assumed, more than 3.3 million
DALYS would be lost annually from diseases related to
Vitamin D deficiency. Importantly, this is not the current
situation.  Although research suggests that many people may
have lower vitamin D levels than might be optimal, these are
not in the range that causes the above-mentioned bone
diseases.  Indeed, rickets and osteomalacia are uncommon
diseases.  In most circumstances, minimal casual exposure
to UVR is sufficient to maintain vitamin D at a level that
avoids these health problems.

    Over-exposure to UVR, rather than under-exposure,
therefore remains the primary public health concern.  The
detailed and appropriate sun exposure advice to avoid
diseases of excessive UVR exposure and of vitamin D
deficiency is best framed by local health authorities,
taking into account the skin type of local populations and
ambient UVR of the region.

    Prevention of UVR overexposure -- WHO recommendations

    -- Limit time in the midday sun: The sun's UV rays are
the strongest 
       between 10 a.m. and 2 p.m( = 2 hours each side of
the solar noon).  To 
       the extent possible, limit exposure to the sun
during these hours.

    -- Use shade wisely: Seeking shade when UV rays are the
most intense is 
       recommended, however, shade structures such as
trees, umbrellas or 
       canopies do not offer complete sun protection. The
shadow rule: "Watch 
       your shadow -- Short shadow, seek shade!"
serves as a simple aide-
       memoire.

    -- Wear protective clothing: A hat with a wide brim
offers good sun 
       protection for eyes, ears, face, and the back of
your neck.  Sunglasses, 
       with adequate side protection that provide 99 to 100
percent UV-A and 
       UV-B protection will greatly reduce eye damage from
sun exposure.  
       Tightly woven, loose fitting clothes will provide
additional protection 
       from the sun.

    -- Use sunscreen: Liberal application of a
broad-spectrum sunscreen of SPF 
       15+ and re-application every two hours, or after
working, swimming, 
       playing or exercising outdoors, can help protect the
skin from UVR.  
       The application of sunscreens exposure should not be
used to prolong 
       sun exposure but rather to protect the skin when
exposure is 
       unavoidable.

    -- Avoid sunlamps and tanning parlours: Sunbeds damage
the skin and 
       unprotected eyes and are best avoided entirely.  WHO
recommends that 
       youth under the age of 18 do not use them at all.

    -- Know the UV index: The UV index is a measure of UV
radiation (see 
       http://www.who.int/uv ).  The higher the UV index,
the higher the risk 
       of skin and eye damage.  Use the UV index to plan
sun-safe outdoor 
       activities.  When the UV Index predicts radiation
levels of 3 (moderate) 
       or above, sun safety practices should be taken.

    -- Protect children: Children are generally more
susceptible to 
       environmental hazards than adults.  During outdoor
activities, they 
       should be protected from high UV exposure as above,
and babies should 
       always remain in the shade.  The promotion of sun
protection in schools 
       is particularly important to make children aware of
the risks of 
       overexposure and how to avoid it.  WHO has developed
special programmes 
       to address this issue.  For more information see
http://www.who.int/UV .

    Prevention of vitamin D deficiency 

    The risks of vitamin D deficiency due to under-exposure
to UVR have been much publicized recently.  Considerable
research is currently underway to better understand these
risks and appropriate levels of sun exposure. Populations
who have very low sun exposure, such as institutionalized
individuals (e.g. prisoners), deeply pigmented persons
living in low UVR settings (e.g. at high latitude) or those
who, for religious or cultural reasons cover their entire
body surface when they are outdoors, should, in
consultation with their doctor, consider a vitamin D
nutritional supplement. For the large majority of people
worldwide, prevention of overexposure to UVR (using the
above advice) remains the main health concern.

    WHO's role

    WHO, through the global INTERSUN project, has been
providing scientific information and practical advice on
the health impact and environmental effects of UVR exposure
since 1995.  INTERSUN conducts activities aimed at reducing
the global burden of disease from excessive UVR exposure. 
Other international organizations (UNEP, WMO, IARC and
ICNIRP), and several WHO collaborating centers are actively
involved in INTERSUN.

    For further information: 

    The full report "Solar ultraviolet radiation --
global burden of disease from solar ultraviolet
radiation" is available online under
http://www.who.int/uv .

    Additional information on INTERSUN, the global UV
project as well as on practical tools and resources is
available at http://www.who.int/uv/intersunprogramme/en/ .

    Information requests should be sent to mediainquiries
at [e-mail] or phone: [phone]; fax:
[phone] .

    All press releases, fact sheets and other WHO media
material may be found at http://www.who.int .

SOURCE  World Health Organization