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Sunscreens: Do They Cause Skin Cancer?
With complete references for researchers
In 1991 Professor Johan Moan of the Norwegian Cancer
Institute made an astounding discovery. He found that the yearly incidence of
melanoma in Norway had increased by 350% for men and by 440% for women during
the period 1957 to 1984. He also determined that there had been no change in
the ozone layer over this period of time. He concludes his report in the
British Journal of Cancer by stating "Ozone depletion is not the cause of the
increase in skin cancers"(1).
SKIN CANCER
There are three major forms of skin cancer.
BASAL CELL CARCINOMA is the most common form of skin cancer. It occurs most
frequently in men who spend a great deal of time outdoors and primarily
produces lesions on the head and neck(2). Basal cell carcinoma rarely spreads
throughout the body but can invade neighboring bone and nerves(3).
SQUAMOUS CELL CARCINOMA is the second most common skin cancer. It primarily
affects people who sunburn easily, tan poorly, and have blue eyes and red or
blonde hair. Squamous cell carcinoma most commonly develops from actinic
kurosis and can metastasize if left untreated. Squamous cell carcinoma of the
lip is 12 times more common among men than among women(4).
MALIGNANT MELANOMA is the rarest form of skin cancer but is the most deadly. It
affects the cells which produce melanin and seems to be more prevalent among
city-dwellers than among people who work out-of-doors. It does not necessarily
occur on sun-exposed areas of the body and is thought to be linked to brief,
intense periods of sun exposure and a history of severe sunburn in childhood or
adolescence. Malignant melanoma metastasizes easily and is often fatal if not
caught in time(2,5).
The skin cancer epidemic is a worldwide phenomenon. In 1978 there were
approximately 480,000 cases of non-melanoma skin cancer in the United States
alone. This is expected to rise to over one million in 1994(6). Malignant
melanoma is growing at a rate of 7% per year in the United States. In 1991
cancer experts estimated that there would be about 32,000 cases during the year
of which 6,500 would be fatal(7). In Canada melanoma incidence rose by 6% per
year for men and by 4.6% per year for women during the period 1970- 1986(8).
Australia has the highest melanoma rate in the world. For men the rate doubled
between 1980 and 1987 and for women it increased by more than 50%(9). It is now
estimated that by age 75 two out of three Australians will have been treated
for some form of skin cancer(10).
If the ozone layer has not yet changed significantly except at the poles, then
what is causing the enormous increase in skin cancer?
The sunscreen connection
The Australian experience provides the first clue. The
rise in melanoma has been exceptionally high in Queensland where the medical
establishment has long and vigorously promoted the use of sunscreens.
Queensland now has more incidences of melanoma per capita than any other place.
Worldwide, the greatest rise in melanoma has been experienced in countries
where chemical sunscreens have been heavily promoted(11).
Drs. Cedric and Frank Garland of the University of California are the foremost
opponents of the use of chemical sunscreens. They point out that, although
sunscreens do protect against sunburn, there is no scientific proof that they
protect against melanoma or basal cell carcinoma in humans(11). There is,
however, some evidence that regular use of sunscreens helps prevent the
formation of actinic kurtosis, the precursors of squamous cell carcinoma(12).
The Garland brothers strongly believe that the increased use of chemical
sunscreens is the primary cause of the skin cancer epidemic. They emphasize
that people using sunscreen tend to stay longer in the sun because they do not
get a sunburn - they develop a false sense of security(7). Chemical sunscreens
are formulated to absorb UVB radiation, they let most of the UVA rays
through(7). UVA rays penetrate deeper into the skin and are strongly absorbed
by the melanocytes which are involved both in melanin production (sun tanning)
and in melanoma formation(11). UVA rays also have a depressing effect on the
immune system(13).
ULTRAVIOLET RADIATION
UVA rays constitute 90-95% of the ultraviolet light
reaching the earth. They have a relatively long wavelength (320-400 nm) and are
not absorbed by the ozone layer. UVA light penetrates the furthest into the
skin and is involved in the initial stages of sun tanning. UVA tends to suppress
the immune function and is implicated in premature aging of the skin(2,13,14).
UVB rays are partially absorbed by the ozone layer and have a medium wavelength
(290-320 nm). They do not penetrate the skin as far as the UVA rays do and are
the primary cause of sunburn. They are also responsible for most of the tissue
damage which results in wrinkles and aging of the skin and are implicated in
cataract formation(2).
UVC rays have the shortest wavelength (below 290 nm) and are almost totally
absorbed by the ozone layer. As the ozone layer thins UVC rays may begin to
contribute to sun burning and premature aging of the skin(2).
All forms of ultraviolet radiation are believed to contribute to the
development of skin cancer(2).
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