The
Southern Ocean is one of the world's most productive marine ecosystems, home to
huge numbers of penguins, seals, and bottom plants, and a major supplier of
nutrients carried to other parts of the world by undersea currents. Little is
known about the effect of UV-B on marine life, particularly the microscopic
algae called phytoplankton that form the foundation of the undersea food chain.
These tiny plants capture the sun's energy through photosynthesis, providing
food for microscopic animals.
phytoplankton
images
They
are eaten by krill, which sustain the Antarctic's abundant seals, penguins, and
baleen whales.
Less
phytoplankton means less food for these animals to eat. It is estimated that a
16 % ozone depletion could result in further losses in Phytoplankton, which
would lead to a loss of about 7 million tons of fish per year. With the human
food supply already strained due to demands of an ever-increasing population,
small reductions resulting from UV damage may be disastrous to many people,
especially the poor and indigenous people.
UV
Rays enter thehuman body
Researchers
say it's clear that UV-B harms Antarctic microbes. Dr Patrick Neale, of the
Smithsonian Environmental Research Center, has predicted that phytoplankton
photosynthesis declines by as much as 8.5 per cent under the worst conditions.
DNA
It
also damages the DNA of marine bacteria and the larvae of starfish and urchins,
they say. And it even alters ocean chemistry, creating potentially dangerous
substances in the water itself.
"This
refers to the fact that UV radiation is involved in a number of photochemical
reactions in seawater (including the hydrolysis/splitting of water molecules)
that produce radicals (hydroxyl, peroxide, superoxide, etc.). These radicals are
very reactive and can cause biological damage by oxidizing
biological molecules. It's really dramatic what the changes in ozone
levels will do to rates of DNA damage and inhibited development," says
biologist Deneb Karentz of the University of San Francisco. "If you have a
30 per cent decline in ozone, that doesn't mean a 30 per cent decline in a given
biological process - it could be a lot more than that". Experts predict
that an estimated 10 % reduction in the ozone layer will result in a 25 %
increase in non-melanoma skin cancer rates for temperate latitudes by the year
2050.
Deneb Karentz of the University of San
Francisco
Professor of Environmental
Science and Biology Chair, Department of Biology
Photograph taken near
Palmer Station, a US research base on Anvers Island along the Antarctic
Peninsula
The
burning goes deeper however, than sunburn, skin cancers, and cataracts. Wearing
certain sunglasses may enhance exposure of the lens and retina to harmful UV
rays, because the iris opens wider to compensate for the reduced visible light
and then more penetration of UV can reach the retina. Through other similar
mechanisms, UV rays can suppress the human immune system leaving the body
vulnerable to many diseases caused by bacteria and viruses entering through or
affecting the skin. While darker skinned individuals are less likely to contract
a skin cancer from sun exposure, dark skin is not a protection against immune
suppression by UV. But dark skin does require a greater dosage of UV than white
skin to initiate immune suppression.
Increased
exposure to UV rays in animals and humans has been linked to elevated risk from
the following diseases: the herpes viruses, the human immunodeficiency virus
HIV- 1, a variety of papilloma viruses, leishmaniasis, malaria, forms of
tuberculosis, leprosy, lupus erthematodes, dermatitis, E. coli, and
Staphylococcus aureus. Since UV rays readily damage DNA in all cells, it is not
unrealistic to hypothesize that this will play an additional role in the
mutation of existing disease bacteria and viruses and may produce totally new
strains of pathogens. Physicians are finding that infection and disease is a
greater global challenge than cancer, as people of all skin pigmentation are at
equal risk from the effects of immuno-suppression. Geographic areas of poor
public health are at even greater risk.
Australian
Skin Cancer
Australians
suffer the highest rates of skin cancer in the world. Each year, around 1,200
Australians die from what is an almost totally preventable disease. Everyone can
develop skin cancer; however, some people may be at higher risk than others, due
to a range of factors.
Australia exposed to more UV
Ultraviolet (UV) radiation levels in Australia are higher than in Europe, even
during summer. Being located close to the ozone hole over the Antarctic means
much higher, more severe levels of UV radiation get through to ground level.
During summer, the earth's orbit brings Australia closer to the sun than Europe
during its summer, resulting in an additional seven per cent solar UV intensity.
This, coupled with our clearer atmospheric conditions, means Australiansare
exposed to up to 15 per cent more UV than Europeans.
First launched by a cartoon seagull
singing ‘Slip! Slop! Slap!’ on TV screens in 1980,
SunSmart adopted its name and mission in
1988. An initiative of The Cancer Council Victoria and supported by the
Victorian Health Promotion Foundation, SunSmart was developed to combat
spiralling skin cancer incidence and mortality rates.
Since then, attitudes towards tanning and
sun protection have changed dramatically. Australians have realised the pitfalls
of their sun-loving, outdoor lifestyle and are taking preventative measures to
reduce their risk of sun damage and skin cancer. Research by The Cancer Council
Victoria shows SunSmart’s messages have reached a majority of Australians and
had a stong impact on their behaviour.
Consequently, skin cancer deaths have
slowed and for females, have even started to decline. More Australians are
detecting skin cancers early, increasing their chances of surviving the disease.
More than 1 million new cases
of skin cancer will be diagnosed in the United States this year
1 in 5 Americans will develop
some form of skin cancer during their lifetime
There will be about 108,230
new cases of melanoma in 2007 — 48,290 in situ (noninvasive) and 59,940
invasive (33,910 men and 26,030 women).
In 2007, at current
rates, a person has a one in 33 chance of developing melanoma (both in situ
and invasive). The risk of developing invasive melanoma is one in 63.
Invasive melanoma is the sixth
most common cancer in men and women.
Melanoma is the second most
common cancer in women aged 20-29.
One American dies of melanoma
almost every hour (every 65 minutes).
In 2007, 8,110 deaths will be
attributed to melanoma — 5,220 men and 2,890 women. Older Caucasian males
have the highest mortality rates from melanoma.
An estimated 10,850
people in the United
States will die of skin cancer this year, 8,110 from melanoma and 2,740 from
other skin cancers.
The incidence of melanoma has
increased 690 percent from 1950 to 2001, and the overall mortality rate
increased 165 percent during this same period.
More than 75 percent of skin
cancer deaths are from melanoma.
Both basal cell carcinoma and
squamous cell carcinoma have a better than 95 percent five-year cure rate if
detected and treated early.
The five year survival rate
for people whose melanoma is detected and treated before it spreads is 99
percent.
Between 1996 and 2002, the
five year survival rate for melanomas detected at all stages increased to 92
percent from 82 percent between 1975 and 1977.
Credit: American Cancer Society's
2007 Facts & Figures
The World Health Organization
estimates that as many as 60,000 people a year worldwide die from too much sun,
mostly from malignant skin cancer. Of these deaths, 48,000 are from melanoma,
and 12,000 are from other skin cancers. About 90 percent of these cancers are
caused by ultraviolet light from the sun.
Health
Effects of Overexposure to the Sun
Since the appearance of an ozone hole
over the Antarctic in the early 1980s, Americans have become aware of the
health threats posed by ozone depletion, which decreases our atmosphere's
natural protection from the sun's harmful ultraviolet (UV) rays. This fact
sheet provides a quick overview of the major health problems linked to
overexposure to UV radiation:
Skin Cancer
The incidence of skin cancer in the
United States has reached epidemic proportions. One in five Americans will
develop skin cancer in their lifetime, and one American dies every hour from
this devastating disease. Medical research is helping us understand the causes
and effects of skin cancer. Many health and education groups are working to
reduce the incidence of this disease, of which 1.3 million cases have been
predicted for 2000 alone, according to The American Cancer Society.
Melanoma
Melanoma, the most serious form of
skin cancer, is also one of the fastest growing types of cancer in the
United States. Many dermatologists believe there may be a link between
childhood sunburns and melanoma later in life. Melanoma cases in this
country have more than doubled in the past 2 decades, and the rise is
expected to continue.
Nonmelanoma Skin Cancers
Nonmelanoma skin cancers are less
deadly than melanomas. Nevertheless, left untreated, they can spread,
causing disfigurement and more serious health problems. More than 1.2
million Americans will develop nonmelanoma skin cancer in 2000 while more
than 1,900 will die from the disease. There are two primary types of
nonmelanoma skin cancers. These two cancers have a cure rate as high as 95
percent if detected and treated early. The key is to watch for signs and
seek medical treatment.
Basal Cell Carcinomas are the
most common type of skin cancer tumors. They usually appear as small, fleshy
bumps or nodules on the head and neck, but can occur on other skin areas.
Basal cell carcinoma grows slowly, and rarely spreads to other parts of the
body. It can, however, penetrate to the bone and cause considerable damage.
Squamous Cell Carcinomas are
tumors that may appear as nodules or as red, scaly patches. This cancer can
develop into large masses, and unlike basal cell carcinoma, it can spread to
other parts of the body.
Other Skin Damage
Other UV-related skin disorders include
actinic keratoses and premature aging of the skin. Actinic keratoses are skin
growths that occur on body areas exposed to the sun. The face, hands,
forearms, and the "V" of the neck are especially susceptible to this
type of lesion. Although premalignant, actinic keratoses are a risk factor for
squamous cell carcinoma. Look for raised, reddish, rough-textured growths and
seek prompt medical attention if you discover them. Chronic exposure to the
sun also causes premature aging, which over time can make the skin become
thick, wrinkled, and leathery. Since it occurs gradually, often manifesting
itself many years after the majority of a person's sun exposure, premature
aging is often regarded as an unavoidable, normal part of growing older. With
proper protection from UV radiation, however, most premature aging of the skin
can be avoided.
Eye Damage
UV exposure can cause health concerns
other than cancer. Cumulative damage from repeated UV exposure may contribute
to chronic eye disease. UV rays can harm the cornea--the transparent front
part of the eye. Because long-term sunlight is thought to cause cataracts or
clouding of the lens of the eye, UV-protective sunglasses are
recommended.
source: United States Environmental
Protection Agency
The SunWise Program is an
environmental and health education program that aims to teach the public how
to protect themselves from overexposure to the sun through the use of
classroom-based, school-based, and community-based components.
Skin cancer
and ultraviolet-B radiation under the Antarctic ozone hole: Southern
Chile, 1987-2000
Background: Punta
Arenas, Chile, the southernmost city in the world (53°S), with a
population of 154 000, is located near the Antarctic ozone hole (AOH)
and has been regularly affected by high levels of ultraviolet-B (UV-B)
radiation each spring for the last 20 years. Large increases in UV-B
associated with the AOH have been measured with increases in UV-B at 297 nm
of up to 38 times those of similar days with normal ozone. Recently we
reported significant increases in sunburns during the spring of 1999 on
days with low ozone because of the AOH.
Methods: A
surveillance of skin cancers occurring from 1987 to 2000 was performed.
Age, sex, location, type of skin cancer and skin phototype were recorded.
A Brewer Spectrophotometer was used in order to obtain in situ
measurements of ozone and UV-B. Total Ozone Mapping Spectrometer (TOMS)
data from National Aeronautics and Space Administration (NASA) was used in
order to establish pre-ozone hole climatology.
Results: Ozone levels
as low as 145 DU (Dobson Units) were recorded, a 56% decrease in
ozone, and UV-B levels up to 4.947 J/m2. These levels are
close to summertime levels at mid latitudes. For the 14-year period - from
1987 to 2000 - 173 cases of skin cancer were diagnosed, 65 during the
first 7 years, 108 during the second, an increase of 66%. Cutaneous
malignant melanoma (CMM), 19% of the cases, increased by 56%, raising the
rate from 1.22 to 1.91 per 100 000. Non-melanoma skin cancer (NMSC),
81% of the total, increased the rate from 5.43 to 7.94 per 100 000 (P < 0.05),
a 46% increase. Patients with CMM and NMSC had skin phototypes I-II in 59%
and 54% of cases, respectively. Days with more than 25% ozone loss
occurred in 143 days during the last 20 springs. Significant
increases of UV-B were observed under ozone hole conditions, especially
around 300 nm, the most carcinogenic wavelengths.
Conclusions: Highly
unusual ozone loss and UV-B increases have occurred in the Punta Arenas
area over the past two decades resulting in the non-photoadapted
population being repeatedly exposed to an altered solar UV spectrum with a
greater effectiveness for erythema and photocarcinogenesis. This
phenomenon has not previously been reported over other populated areas and
an additional increase in the skin cancer rate attributable to the
Antarctic ozone hole may be occurring. Research on the clinical and
subclinical impact of these abnormalities is urgently needed.
Source: Abarca, Jaime F. & Casiccia, Claudio C. (2002) Skin cancer and
ultraviolet-B radiation under the Antarctic ozone hole: southern Chile,
1987-2000. Photodermatology, Photoimmunology & Photomedicine 18 (6),
294-302. doi: 10.1034/ j.1600-0781.2002.02782.x
