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As is common knowledge, the tanning process is credited to what is called ultraviolet radiation or UVR. However, what is not known is that there are different kinds of UVR; UVA (90-95% of UVR that reaches the earth), UVB (5-10% of UVR that reaches the earth) and UVC (filtered out by the ozone layer). UVA penetrates to the deeper dermal layer of skin and UVB stays mostly epidermal. However, UVB has been found to be much more potent with respect to its biological effects.
Commercial tanning beds used to be composed of bulbs that primarily gave off UVA and had a UVB content of only about 0.5%-2.0% because of its potency. However, the recent trend has been to add more UVB radiation back into beds to better simulate natural sunlight. The beds of today now have a UVB content of about 5.0%-9.5%.
Different Types of Tanning and their Mechanisms
The two types of tanning that are produced by UVR are immediate and delayed. An immediate tan is the darker, bronze coloring that shows up during tanning and immediately afterwards. This color, second to UVA and visible light, fades as soon as in a few minutes or as long as in a couple of hours and therefore has little or no cosmetic benefit. While the precise mechanism is still unclear for the immediate tan, it has been suggested that it is due to the relocation of preexisting melanin in the skin; rearrangement of melanosomes within keratinocytes, extension of melanocytic dendrites, or the oxidation of melanin by oxygen radicals. On the other hand, a delayed tan refers to the longer lasting change in color which develops days after exposure. A delayed tan is more efficiently produced by UVB than UVA, but UVA is able to induce this kind of tan in doses that are less than MED (minimal erythema dose). The mechanism for delayed tanning: increased production and transfer of melanosomes to keratinocytes.
Tanning and the production of melanin is a protective measure that the skin takes in order to guard against further damage due to UVR. Yes, all tanning is a result of some sort of UVR damage. This then poses an important question, if tanning is a protective mechanism against cellular damage, why is there a debate about whether or not tanning is detrimental?
Role of Skin Type in Tanning
It is very important to be aware of the fact that not all people are capable of achieving a tan and those who are at the highest risk for skin cancer are also these “poor tanners” normally with Type I or Type II skin. (Type I refers to those who always burn and never tan. Their skin reddens and freckles, but does not tan. Type II refers to those who burn easily and tan minimally. Using sunless tanner if you fall into the category of one of these skin types will be more effective. You will not get much cosmetic benefit from regular tanning and are just putting yourself at risk for the detrimental effects of UVR. Also all skin types, even type V, should use sunscreen.
So why do people tan indoors?
Most indoor tanning enthusiasts today are primarily interested in tanning for cosmetic reasons. They want to obtain that elusive dark sexy tan seen so often in today’s media, including all over Hollywood. Our culture believes that a tan is a mark of beauty and represents success and happiness. This idealization of tan skin is actually a recent development in our society.
In addition to the cosmetic benefits, there are those who tan as a therapy for dermatological conditions such as acne, eczema, and psoriasis. This is actually called phototherapy and is a real treatment normally regulated by a physician. During treatment, UV light is used in conjunction with psoralen (a medication that makes skin much more sensitive to ultraviolet rays, and more specifically UVA rays, and has the potential to produce catastrophic burns if disregarded). Phototherapy IS very effective for many dermatologic conditions. However, commercial tanning parlors use different UVA and UVB bulbs and no psoralen and therefore are inherently not as effective for treatment. Doctor supervision along with specialized UVA bulbs and psoralen are the best way for a patient to this kind of therapy in a safe manner.
Furthermore, there are those that site psychological benefits as one of their reasons for tanning. They crave that relaxed feeling that 83% of indoor tanners report experiencing post-tanning. Also, light exposure in general helps to prevent/treat seasonal affective disorder or SAD; a depressive disorder. The device behind this is that when exposed to sunlight, infrared radiation gives the warm glow feeling to skin, and visible light is responsible for the positive effect on mood.
Many people, before vacationing or before summer, weddings, prom, etc., will use indoor tanning booths to achieve a “base tan”. This base tan is a tan achieved in an indoor booth that is believed to help prevent sunburn. Studies have shown that the base tan attained in regular commercial beds is about equivalent to SPF of 4. UVB tanning is actually more protective than the mainly UVA tan that from most tanning beds. This is due to the fact that UVB-induced tans result in pigment dispersed throughout the epidermis, whereas UVA-induced tans are primarily confined to the basal layer right above the dermis. However, both types of tans (UVB and UVA-induced) were found to protect significantly against UVB-induced DNA damage. Nevertheless, since UVA tanning does not protect against further UVA exposure, and damage is done in the process of getting a UVA tan (inflammation and Bessel thickening), it can be concluded that an indoor tan does little to protect against subsequent sun exposure.
Lastly, some tanning industries claim that tanning is beneficial due to the fact that it produces vitamin D (an essential vitamin required for bone integrity and calcium homeostasis). The process of synthesizing Vitamin D starts in the skin when UVB rays convert 7-dehydrocholesterol into pre-vitamin D3 or vitamin D is ingested orally. Then, this pre-vitamin D3 or ingested vitamin D moves to the liver where it is hydroxylated, and finally, transferred to the kidney where it becomes the active form of vitamin D, 1,25 dihydroxy vitamin D. While it is true that vitamin D is very necessary in the human body, vitamin D can just as easily be ingested and effectively used in the body.
The Effects of UVR
The first step of the biological effects of UVR is when the energy of photons (radiation) striking the skin is soaked up and damages a molecule (a chromophore) that is capable of absorption in that particular wavelength. Common chromophores in the skin are DNA, proteins, lipids, and urocanic acid. Biological effects produced by this mechanism can be divided into two categories: acute and chronic.
The most prevalent and overt effect of UVR is what is commonly known as a sunburn, scientifically named erythema. The characteristics of erythema are inflammation, warmth, pain, and swelling. Although it was previously believed that sunburn was caused primarily by UVB (UVB was referred to as “sunburn rays”), it has been discovered that UVA rays can also cause erythema, although the UVA dose has to be 500 to 1000 times greater. Erythema resulting from UVA has a much different course than sunburn resulting from UVB. UVA induced sunburn is immediate. Erythema is immediately present and peaks right after exposure, but may be biphasic; fading quickly and then returning hours later. On the other hand, UVB induced erythema shows hours after exposure and peaks 12 to 24 hours after exposure. Both types of sunburn do follow the above mentioned mechanism; however the subsequent steps are unclear. It has been suggested that DNA is the primary chromophore for erythema.
There is concern about the relationship between indoor tanning and outdoor UVR exposure with respect to erythema and other biological effects due to the fact that UVL exposure is additive. This means that if someone tans indoors, but does not reach the MED (minimal erythema dose) in the tanning bed, they could very well reach MED by spending any time in natural sunlight. In addition to indoor UVR and outdoor sunlight’s additive properties, UVA and UVB are photoadditive as well. Even though they have different wavelengths, their energies still add together to produce erythema. The Center for Disease Control calculated that approximately 700 visits to an emergency room in a single year were due to burns from indoor tanning beds.
Short-term undesirable effects from indoor tanning include pruritus, xerosis, and nausea. Also, some skin diseases have been observed to develop after indoor tanning. These diseases include pseudoporphyria, polymorphous light eruption, disseminated superficial actinic porokeratosis, mid-dermal elastolysis, and actinic granulomas. Not to mention, preexisting diseases like systemic lupus erythematosus, polymorphous light eruption, porphyria, and rosacea can become aggravated or intensified by UV exposure.
Another target area for the effects of UVR is the eyes. The UV exposure incurred in tanning beds has the potential to produce corneal burns. With natural exposure the orientation of the eyes is such that they do not receive too much UVR because they are protected by the eye sockets and eye brows. However, with an indoor tanning bed, the eyes are directly attacked by UVR. Therefore rigorous use of protective eyewear is essential. This is why FDA guidelines now mandate that protective goggles are to be provided to all tanning salon patrons.
Photoaging is a predominant chronic effect of tanning that is not easily recognizable in young tanners, however becomes very apparent over time. The effects that are second to photoaging differ greatly from the effects that are due to the intrinsic aging process. Chronically exposed photoaging skin is characterized as coarse, leathery, inelastic, dry, yellowish, deeply wrinkled, unevenly pigmented and with brown spots.
Perhaps the most significant potential risk from UVR exposure, indoor or outdoor, is the development of skin cancer. The three types of skin cancer that are most prevalent: squamous cell carcinoma, basal cell carcinoma, and melanoma. Recently, the incidence of skin cancer has been rapidly escalating and is now approaching epidemic size. The United States and Schandinavia are at the forefront of this increase with the highest rates of skin cancer malignancy in the northern hemisphere. The American Cancer Society estimates that this year 111,900 Americans will have contracted melanoma and one American dies of melanoma every 63 minutes.
Although recent studies using high output UVA lamps have shown that UVA alone can induce skin cancer in experimental animals, UVB has still proven to be three to four times more efficient at inducing skin cancers than UVA. Recently, large controlled epidemiological studies are becoming available that study UVR and skin cancer, however there is a high degree of variability in the studies due to differences in dosing schedules, wavelengths emitted, and latent period allowed. Not to mention, differences in the lifestyles of tanners might confound a study. Because of this, the correlation between tanning and cancer remains slightly controversial with respect to the specific processes and which types of UV radiation and dosage are worse, there is little or no doubt that a correlation does exist and can be due to any kind of UVR. No UV radiation is “safe”.
Although there are certain benefits to tanning including cosmetic, psychological, nutritional, slightly protectional, and UVR is effective treatment of some dermatologic conditions, it is also very clear that there are many risks involved with tanning like basal cell carcinoma, squamous cell carcinoma, melanoma, photoaging, corneal burns, erythema, and other skin irritations. Around the world, there have been many successful efforts to educate the public about the danger of UVR exposure. However, in spite of this increased knowledge, tanning salons are as crowded as ever. Tanning is, as with every known risk from smoking to flying in an airplane, a personal choice.
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