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Protecting Your Skin From The Sun

June 2004

By Dave Tuttle

LE Magazine June 2004
Protecting Your Skin From The Sun
With ongoing depletion of the ozone layer, using sunscreen and taking other
steps to protect against harmful ultravoilet radiation are more important than ever.

By Dave Tuttle

Modest Precautions Make a Difference
Until World War II, the middle and upper socioeconomic classes considered suntans to be vulgar.4 Bodies were covered and hats were worn to preserve pale skin tone. The only people with tans were those who worked outdoors. For the past 50 years, however, the “golden” tan has been venerated as a sign of good health. This has led to a huge escalation in sun exposure and skin cancer.

Recently, growing income levels and leisure time have led to more people engaged in outdoor recreation and vacationing in sunny climes. Rising global temperatures have also had an effect, as noted in an article in Physics in Medicine and Biology.11 In northern Europe and Russia, for example, rising temperatures have made winter less oppressive and extended the period of the year suitable for outdoor activities, thus encouraging people to spend more time in the sun. In fact, the study’s author believes that climate change will be the largest determinant of sun exposure—and the consequent incidence of skin cancer—for people in these regions.

What can we do to minimize our exposure to damaging radiation? The first and easiest thing is to rearrange our schedules. Avoid outdoor activities between 10 a.m. and 3 p.m., when radiation is strongest. The relatively minor radiation during the rest of the day will stimulate all the vitamin D we need for good health without causing burns. If you must go out during peak-radiation hours, wear protective clothing and apply a quality sunscreen to all exposed areas.

One of the best ways to protect against the sun is to wear appropriate clothing. While people are often advised to wear hats and long-sleeved garments to minimize the amount of skin exposed to ultraviolet radiation, the assumption that all clothing provides an acceptable level of protection is incorrect. Several studies have shown that, contrary to popular opinion, some textiles provide only limited ultraviolet protection.12 In fact, one-third of commercial summer clothing was found to have a sun protection factor (SPF)-equivalent of less than 15.

A number of textile parameters influence the protection offered by a finished garment, including fabric porosity, type, color, weight, and thickness. Ultraviolet absorbers are sometimes added to yarns to enhance a garment’s protective value, but their availability is limited. Moreover, even if a piece of clothing offers an acceptable level of protection when new, laundering and stretching can reduce its ability to protect. Wetness also keeps clothing from doing its job, so wearing a T-shirt while romping in the surf is no substitute for sunscreen.

Unfortunately, no rating system or approved testing protocols exist to establish the protective value of clothing. Until such a system is developed, try to wear tightly knit garments that are as thick as comfort allows. Even better, apply sunscreen to areas you intend to cover with clothing. There is no such thing as too much protection.

Not All Sunscreens Are Alike
Most everyone is familiar with the SPF system, which accords higher numbers to sunscreens that offer greater levels of protection. Yet most people do not realize that the SPF system is based on the sunscreen’s ability to prevent erythema, technically defined as an inflammatory redness of the skin. An SPF of 15 is usually considered to be a sunblock because, if properly applied, it will prevent redness. This does not mean, however, that ultraviolet damage does not occur. Significant injury, DNA damage, mutations, and carcinogenesis can and do occur with cumulative suberythemal ultraviolet exposure.13 This clearly calls for an SPF higher than 15.

Bear in mind that sweating, water immersion, rubbing off, and photodegradation reduce a sunscreen’s effectiveness. In addition, sunscreen users usually apply only one-quarter to one-half of the thickness (2 mg/cm2) used to measure SPF in the laboratory, which means a sunscreen with an SPF as high as 30 could effectively be rendered one with an SPF as low as 7.5. Frequent and liberal applications of sunscreen therefore are essential to provide the level of protection indicated on the product label.

Even sunscreens with the same SPF are not created equal. A study published in the Journal of Investigative Dermatology found a significant difference in immune-system suppression between two products with an SPF of 15.14 As noted earlier, one of the deleterious long-term effects of ultraviolet radiation is reduced efficiency of the immune system. While the immunosuppressive and carcinogenic potential of the more erythemogenic spectrum is well established, only recently has the contribution of UVA radiation to immune-system suppression been recognized, even though UVA accounts for approximately 90% of total ultraviolet radiation and, unlike UVB, can penetrate glass windows.

The Journal of Investigative Dermatology study compared two sunscreens with an SPF of 15. The first, which contained avobenzone, octocrylene, and octyl salicylate, had a UVA protection factor of 10 based on an in-vivo pigment-darkening method. The second product, made from zinc oxide and octyl methoxycinnamate, had a UVA factor of 2. Nonlinear regression analysis based on changes in skin-fold thickness revealed that the first sunscreen had an immune protection factor of 50, while the zinc-oxide formulation had an immune protection factor of 15 (equal to its SPF). In other words, the product with avobenzone was more than three times more protective. Given the immune system’s importance in preventing the initiation and growth of skin cancer, it is advisable to use a sunscreen that contains avobenzone and other ingredients that maximize UVA protection as well as offer UVB protection.

Protecting the Body’s Largest Organ
Now more than ever, we need to take preventive action to protect our skin. The ongoing radiation assault from the ozone layer’s depletion makes this a vital health concern. While everyone looks better without leathery skin, there is more than vanity at stake—your skin is your body’s largest organ, and it deserves the highest level of respect.

An extensive study in Archives of Dermatology reveals just how important this is.15 On four consecutive days, a sunscreen with an SPF of 15 was applied to four sites on the buttocks of 18 women ranging in age from 20 to 55. The sunscreen was applied 30 minutes before exposure to two doses of ultraviolet radiation sufficient to provoke a minimum level of erythema. Of the four sites of application, one was treated with sunscreen daily, while the remaining three were treated on three of the four days they received radiation, skipping either days two, three, or four. A fifth site served as a control and was not irradiated.

The researchers found there was no significant difference in thymine dimer formation between the irradiated and nonirradiated sites when an application of sunscreen preceded each irradiation. When the sunscreen was not applied for even a single day at this minimal radiation level, however, a statistically significant increase in thymine dimer formation was noted. While the women’s bodies removed some of the dimers from the irradiated areas, 25% of them were still there 72 hours later.

Considering how much time we spend in the sun, it quickly becomes apparent that regular use of sunscreen is essential to protect our skin. If ultraviolet radiation is absorbed regularly, these ongoing concentrations of dimers could accumulate and produce conditions conducive to melanoma and other skin cancers.

The best way to protect against harmful ultraviolet radiation is to minimize sun exposure, wear protective clothing, and liberally apply sunscreen. Your eyes may be the mirrors to your soul, but your skin is what people notice first. And vibrant, healthy skin says a lot about who you are.

New Study: UVA Light More Harmful than Previously Thought

Type A ultraviolet (UVA) light, previously considered less dangerous than type B ultraviolet (UVB) light, “could contribute more significantly to skin cancer than previously assumed,” according to a study recently published in the Proceedings of the National Academy of Sciences.

UVA, which causes skin to age, produces less direct damage to DNA than UVB “and therefore has been considered far less carcinogenic,” wrote the study authors, who were led by Gary Halliday of the Melanoma and Skin Cancer Research Institute in Sydney, Australia.

The researchers studied two types of skin cancer cells to examine the effects of UVA. Most mutations caused by UVA were found in cells deep in the skin, while those caused by UVB were found in superficial layers of the skin.

“Because of the mutagenic effects that UVA waves have on dividing stem cells in the skin, the researchers propose that this type of ultraviolet light could contribute more significantly to skin cancer than previously assumed,” the Australian study team concluded. “Given the traditional emphasis on UVB, these results may have profound implications for future public health initiatives for skin cancer prevention.”


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2. Scarlett WL. Ultraviolet radiation: sun expo- sure, tanning beds, and vitamin D levels. What you need to know and how to decrease the risk of skin cancer. J Am Osteopath Assoc. 2003 Aug;103(8):371-5.

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15. Al Mahroos M, Yaar M, Phillips TJ, Bhawan J, Gilchrest BA. Effect of sunscreen applica- tion on UV-induced thymine dimers. Arch Dermatol. 2002 Nov; 138(11):1480-5.