Download Ultraviolet radiation: sun exposure, tanning beds, and vitamin D

REVIEW ARTICLE
Ultraviolet Radiation: Sun Exposure, Tanning Beds,
and Vitamin D Levels. What You Need to Know and
How to Decrease the Risk of Skin Cancer
William L. Scarlett, DO
This year, more than one million new cases of skin cancer
will be diagnosed in the United States and an estimated
9800 individuals will die of the disease. Despite recent
public education efforts and increased public awareness
about the importance of the use of sunscreen and avoidance of ultraviolet radiation, the incidence of melanoma has
more than tripled among white Americans from 1980 to
2001. This increase in cancer rates means that one person
dies of melanoma in this country every hour of every day.
The answer to this increasing problem is not a simple
one, but public education seems to be a common starting
point. The American Cancer Society and the American
Academy of Dermatology have published recommendations with regard to sun exposure and sunscreen use. However, patients often ask questions that are not as easily
answered. Questions such as, Which sunscreens are the
safest? Are tanning beds safe? If I limit my sun exposure, do
I need to take vitamin D supplements? If I tanned as a
teenager, is the damage already done? How do I treat sunburn? This article provides a review of the current literature regarding these issues and provides the facts family
physicians need to answer common patient questions.
The author discusses the mechanisms of sun damage, the
facts on tanning beds, and the importance of supplementing vitamin D.
H
alf of all newly diagnosed cancers are skin cancers.1,2
Ultraviolet irradiation is the predominant risk factor for
the development of both melanoma and nonmelanoma
skin cancers.1,3
Although most patients are aware that ultraviolet (UV)
exposure includes exposure to sunlight, they may not be
aware that they are exposed to ultraviolet light when using
tanning beds, when working with UV lamps, and when
receiving therapeutic exposure in the treatment of some
skin disorders.4 The American Cancer Society, the Amer-
Dr Scarlett is a cosmetic surgery fellow at The Body Sculpting Center in Scottsdale, Ariz.
Address correspondence to William L. Scarlett, DO, The Body Sculpting
Center, 2255 N Scottsdale Rd, Scottsdale, AZ 85257-2124.
E-mail: [email protected]
Scarlett • Review Article
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ican Academy of Dermatology, the US Department of Health
and Human Services, and the US Environmental Protection
Agency all have similar recommendations regarding sun
exposure: wear protective clothing, apply sunscreen with a sun
protection factor (SPF) of at least 15 and avoid UV exposure
between the peak exposure hours of 10 AM and 3 PM.1,5-7 The
American Academy of Dermatology has specific recommendations on sunscreen use as noted in Figure 1.
Children and Skin Types
When discussing skin types, most clinicians use the Fitzpatrick phototype scale, with ratings from I to IV (ie, I: never
tans/always burns, II: sometimes tans/usually burns, III: usually tans/sometimes burns, IV: always tans/rarely burns).
People with fair skin and light hair have an increased risk
for developing both cutaneous malignant melanoma and
basal cell carcinoma.8 Current literature indicates that an individual’s exposure during childhood is a strong determinant
of melanoma risk.3,9-11 Gallagher et al11 note that people who
lived in a sunny environment for more than 1 year before
the age of 10 had a fourfold increase in the risk of melanoma.
In addition, people born in California have higher rates of
melanoma than other Americans, irrespective of their current place of residence.
Melanocytic nevi originate in childhood and are caused
by sun exposure. These acquired nevi increase the risk for
the development of cutaneous malignant melanoma. In casecontrol studies, there is an inverse relationship with children
who used broad-spectrum sunscreen and the development of
new melanocytic nevi.9 Children whose parents required
them to wear sunscreen were more apt to use sunscreen as
adults, which further protects them from the development of
skin cancer.3,12,13 Specific sunscreens have been designed and
are marketed for use in children.
Sunburn
Driscoll and Wagner14 note, “A sunburn is a chemical response
to acute cutaneous solar photodamage due to excessive UV
light exposure.” The principal cause of a sunburn is ultraviolet irradiation at wavelengths between 320 nm and 290 nm
(UVB).6,12 Histologically, upon examination of sun-damaged
skin, physicians will observe dyskeratotic and vacuolated
keritinocytes known as sunburn cells.5,12 There is also a reducJAOA • Vol 103 • No 8 • August 2003 • 371
REVIEW ARTICLE
Table
Commonly Used Sunscreen Ingredients
Ingredient
Protection Range (nm)
UVA Protection*
UVB Protection†
Avobenzone (Parsol 1789)
400 – 320
—
Benzoate 4 methylbenzylidene
300 – 290
—
Dioxybenzone
390 – 250
—
Homosalate
330 – 294
—
Lisadimate (glyceryl p-aminobenzoic acid)
315 – 264
—
Menthyl anthranilate
380 – 260
—
Mexoryl SX‡
400 – 290
Octocrylene
360 – 350
—
Octyl methoxycinnamate
320 – 290
—
Octyl salicylate
320 – 289
—
Padimate O
315 – 290
—
p-Aminobenzoic acid (PABA)
313 – 260
—
Phenylbenzimidazole
340 – 290
—
Roxadimate
330 – 289
—
Sulisobenzone (Eusolex 4360)
375 – 260
—
Titanium dioxide‡
700 – 290
Trolamine salicylate
320 – 260
—
Zinc oxide‡
700 – 200
* UVA indicates long-wavelength levels of radiation, 400 nm – 320 nm.
† UVB indicates short-wavelength levels of radiation, 320 nm – 290 nm.
‡ This ingredient provides total, “broad spectrum” UVA and UVB protection.
tion in the number of Langerhans cells and a general immunosuppressive effect, which is believed to contribute to the photocarcinogenic process. The application of commercially available sunscreen products will reduce the acute affects of UV
irradiation, including the appearance of sunburn cells, the
migration of the Langerhans cells out of the epidermis, as
well as the inflammatory response. The regular use of sunscreen has been found to decrease the number of actinic keratoses and nonmelanoma skin cancers.5
The treatment of acute sunburn is a common dilemma
faced by numerous physicians each summer. Clinical evidence has shown that nonsteroidal anti-inflammatory drugs,
steroids, and antihistamines have little effect on the erythema
caused by these burns. Furthermore, the topical anesthetics
containing benzocaine carry a significant risk of allergic contact dermatitis and are presently not recommended for treatment.12 Pain control and future sunburn prevention are the
two things that physicians can offer patients after they have
been sunburned.
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Sunscreen
According to the Centers for Disease Control and Prevention, 70% of adults in the United States do not protect themselves from sun exposure.13 Even patients who have had skin
cancer previously diagnosed do not change their habits with
regards to the sun. In a study that followed up patients who
had been treated for basal cell carcinoma 1 year after surgical
intervention, 15% did not wear any sunscreen and 42% did not
know what the abbreviation SPF stood for.14 The responsibility
for these lapses rests on any physicians who failed to properly
educate patients when the skin lesion was removed.
High rates of skin cancer have been diagnosed among
occupational groups who work outdoors. In a recent survey
of California construction and highway workers, only 51% had
received any skin cancer education.1 Furthermore, only 30%
wore sunscreen on the day of the survey.1 The US Department
of Labor’s Occupational Safety and Health Administration
does not require skin education of these employees who are
exposed to UV radiation for up to 12 hours each day.
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REVIEW ARTICLE
Physicians need to include questions in their history taking
that screen patients for high exposure to UV radiation. We
should also encourage patients with a high level of risk to
wear protective clothing and use sunscreens. It is believed
that the higher the SPF grading, the more effective protection
the product provides against skin cancer.10 However, commercial brands of sunscreen differ in their active ingredients.
In a study that examined the absorption of these ingredients
across the skin, one ingredient, benzophenone–3, generated
concern.15 The study’s authors15 noted that this ingredient
“demonstrated sufficiently high penetration to warrant further
investigation of its continued application.” All other ingredients tested showed limited absorption. Most of the active
ingredients available in sunscreens and their spectrum of coverage are illustrated in the Table.
There also has been research looking at other topical and
systemic agents for use in protection from solar damage. The
most promising to date is the polyphenolic extract from green
tea. These extracts have been shown to be effective chemoprotective agents against the effects of UV damage including
reducing the number of sunburn cells, reducing the DNA
damage from UV irradiation, and protecting the Langerhans
cells.6 Green tea extracts do not work in the same manner as
sunscreen by blocking UV light, but rather on a cellular level.
Animal models have even demonstrated that if this extract is
added to the water supply, there is cellular evidence of photoprotection.6
Wound Healing
Scientists have demonstrated that skin cancer can occur in
damaged tissue due to burns (ie, Marjolin’s ulcer).16 Physicians need to emphasize the need to protect iatrogenically
damaged tissue as well, specifically any type of surgical site.
Numerous studies demonstrate the ill effects of UV irradiation
preoperatively and postoperatively from laser surgery. It is
easy to see the increased complications of hyperpigmentation
and prolonged inflammation.17 There is further evidence that
any postoperative UV exposure will disrupt the healing process, “aggravat[ing] bulging, infiltration, fibrosis, and hyperpigmentation, thus confirming the necessity of avoiding sun
exposure and using high-factor sunscreens as part of routine
postoperative wound care.”18 Remodeling of a wound can
last up to 1 year and contributes to the development of the tensile strength of the wound.19 Therefore, physicians need to
encourage patients to protect any wound from exposure to UV
radiation—whether that wound is an ulcer or a surgical site.
Checklist
Avoid deliberate excessive exposure to sunlight (eg,
sunbathing or days at the beach).
Wear ultraviolet-blocking sunglasses and protective
clothing, including a wide-brimmed hat, when
exposed to ultraviolet light.
Apply sunscreen 15 to 20 minutes before going
outside.
Use sunscreen every day if you receive daily
exposure to the sun for longer than 20 minutes.
Wear sunscreen with a sun protection factor (SPF)
of at least 15, preferably one that is labeled as
providing “broad spectrum” protection, blocking
long- (UVA [400 nm – 320 nm]) and shortwavelength (UVB [320 nm – 290 nm]) radiation.
One ounce (30 mL) of sunscreen is required to cover
exposed areas of the body completely.
Reapply sunscreen every 2 hours or immediately
after swimming and/or strenuous activity.
Source: American Academy of Dermatology.
MelanomaNet: Prevention. Available at:
http://www.skincarephysicians.com/melanomanet/
prevention.htm. Accessed July 28, 2003.
Figure 1. The American Academy of Dermatology’s current recommendations on sun exposure.
radiation.20 UVA irradiation can cause a sunburn and has
been implicated in both photoaging and nonmelanoma skin
cancers.6 In fact, an estimated 700 emergency department
visits per year are related to the use of tanning beds.20 In the
face of these facts, the industry maintains that this activity is
safe and, in some cases, even healthy.
There is an increasing awareness that UVA (400 nm –
320 nm) can also be damaging to the skin.6 Similar to outdoor
exposure, recreational tanning will cause molecular alterations
that are believed to be essential in the development of skin
cancer. Specifically, DNA alterations and P53 protein expression occur.20 Short-term use of tanning beds can cause longterm skin damage and increase the chances of skin cancer.
Vitamin D
Tanning Beds
On an average day in the United States, more than one million
people spend time in a tanning salon. This is a $2 billion
industry, but only 21 states have regulations in place. As of yet,
the tanning industry has no legal responsibility to provide
data on the carcinogenic effects of tanning to its customers. The
average tanning bulb emits 95% UVA radiation and 5% UVB
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The question arises about protecting people from the sun and
vitamin D deficiency. This is a valid concern considering that
vitamin D deficiency has become an epidemic in adults older
than 50 years.21 Vitamin D deficiency increases the risk of
bone disease, muscle weakness, and possibly certain types of
cancer.13,21-25 Some literature suggests that vitamin D deficiency increases the risk of diabetes mellitus, hypertension,
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Figure 2. The chemical conversion
of vitamin D to the active hormone.
7-dehydrocholesterol (provitamin D3)
Precholecalciferol (previtamin D3)
Cholecalciferol (vitamin D3)
Hydroxylation in liver and kidney
25-hydroxyvitamin D and 1,25 dihydroxyvitamin D (active hormone)
myocardial infarction, and susceptibility to tuberculosis.23
Vitamin D is directly involved in preserving serum calcium levels through increased intestinal absorption, which
has been proven to decrease the risk of colon cancer.26
Vitamin D is not really a vitamin, but a prohormone that
is either consumed orally or produced photochemically in the
skin from 7–dehydrocholesterol.7,24,27 This previtamin is then
converted to the active hormone via the liver and kidney
(Figure 2).7,21
Sunlight exposure is considered the most important source
of vitamin D for humans, though the ability to produce
vitamin D from sunlight exposure decreases with age because
of decreased levels of 7–dehydrocholesterol in the skin.22,24,28
Individuals consume few foods that are naturally high in
vitamin D in a normal diet. Cod liver oil, oily fish, and fortified
milk have vitamin D.13,21,24,28 Several large prospective studies
have shown that vitamin D deficiency does not result from regular sunscreen use.13 However, most authors of recent literature on this subject feel the need to increase the daily recommended dose of vitamin D, whether one is protecting oneself
from sun exposure or not.8,14,21,22,24 In 1997, the Institute of
Medicine of the National Academies increased the recommended intake of vitamin D to 200 IU/d for individuals
younger than 50 years, 400 IU/d for those 50 to 70 years, and
600 IU/d for people older than 70 years. Many investigators
have recommended 1000 IU/d when the patient is avoiding
sun exposure.13,21,22,24 There is no consensus on what level of
vitamin D intake is optimal or safe. The published cases of
vitamin D toxicity with hypercalcemia for which the
25–hydroxyvitamin D and vitamin D doses were known, all
involved intake of 40,000 IU/d.24 If the objective is to optimize an individual’s health, it seems reasonable to recommend a daily dose of 800 IU/d to 1000 IU/d.22,24
Epidemiologic studies13,22,24 have shown a lower rate of
breast cancer and prostate and colorectal carcinomas with
higher serum concentrations of 25–hydroxyvitamin D, and
further research is presently ongoing. Individuals with high
serum concentrations of 25–hydroxyvitamin D3 have been
shown to have a threefold decrease in colon cancer.25 Currently, a large-scale prospective clinical trial, the Women’s
Health Initiative, is attempting to prove by 2007 the validity of
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supplementing vitamin D to lower the risk of breast and colon
cancer.
Comment
Patient histories and physical examinations need to include the
use of tanning beds and sun bathing, as well as work environments. Physicians need to ask patients if they use sunscreen, how often, how much, and what SPF. Parents should
be encouraged to apply sunscreen to their children before
going outdoors to play, limit the time they spend outside
during midday hours, and require the use of hats and sunglasses.
Patients can be assured the use of sunscreen will not cause
vitamin D deficiency, and that vitamin D supplementation is
not only safe, it is also recommended for its health benefits and
potential for cancer protection. Currently, physicians should
be following the age-dependent dosing set forth by the Institute of Medicine of The National Academies with the understanding that these guidelines are under review.
We can decrease the number of patients with skin cancer
by increasing patient education on sun exposure. People need
to be reminded to use sunscreens and wear protective clothing
year-round, not just when they are headed to the beach. Most
new cases of skin cancer are preventable and, with increased
physician involvement, we can lower the number of deaths due
to skin cancer each year.
References
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5. Lock-Andersen J, Knudstorp ND, Wulf HC. Facultative skin pigmentation
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