Skin cancer and Sun-safety basics

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My daughter at 6 months

We are in the midst of a skin cancer epidemic.  Skin cancer is by far the most common malignant neoplasm.  In fact there are more than twice as many skin cancers each year in this country as all other forms of cancer combined. The most common type of skin cancer is basal cell carcinoma , and the second most common type is squamous cell carcinoma. It is estimated that one out of every five Americans will develop skin cancer at some point in their life.  Ultraviolet radiation (UVR) is the cause of the vast majority of the nearly 3.7 million skin cancers which are diagnosed in the US annually. UVR is also responsible for up to 90 percent of the visible changes commonly attributed to aging, including wrinkles, sagging skin and brown spots.

Malignant melanoma, the deadliest form of skin cancer, is also an increasingly important public health problem in the United States and worldwide. The incidence of melanoma has increased 3.1% annually during the past 20 years, which translates to an incidence that is increasing faster than that of any other cancer in the United States. Melanoma is not just a disease of the elderly; it is the second and third most common cancer of women and men in their 20’s respectively.  It is the most common deadly skin cancer of women between the ages of 20 and 35.  Someone dies every hour in this country from melanoma. The current lifetime risk of an American developing invasive melanoma is 1 in 59.  This rate is alarming when contrasted with the 1 in 1500 lifetime risk for Americans born in 1935.   The increased incidence of skin cancer appears to be multi-factorial. Sun exposure, both recreational and occupational, changing patterns of dress favoring more skin exposure, ozone depletion and increased life expectancy are likely contributing factors. Additional risk factors including family and personal history of skin cancer, immunosuppression, and carcinogens may also influence developing and dying from skin cancer. People at highest risk include those individuals with light skin and eyes, an inability to tan, freckle easily and have a large number of typical or atypical moles.  Of all these risk factors, sun exposure, is the only established modifiable cause of skin cancer.

The skin is the most exposed organ to environmental ultraviolet radiation (UVR) and to its related effects. The sun emits UVR waves that range from 200 to 400nm. Solar radiation that reaches the earth’s surface comprises approximately 95% UVA (320-420nm) and 5% UVB (290-320nm) rays.  UVB is largely responsible for sunburn, while UVA rays, which penetrate the skin more deeply, are associated with wrinkling, sagging, leathering and discoloration; these changes are also referred to as the effects of photoaging. UVA rays are relatively constant throughout the day and the year. They also can penetrate through window glass, so you are at risk of exposure even when indoors and in your car.  UVB rays, in contrast, have greater intensity in summer than in winter, at midday than in morning or late afternoon, and in places closer to the equator and at high altitudes. It’s important to be aware that certain surfaces reflect the sun’s UV rays, allowing them to hit your skin and eyes twice. Not only does water reflect an extra 10 percent of UV light ; UVR can penetrate water to a depth of 60cm resulting  in significantly increased exposure.

It is well established that there is a strong causal relationship between UV exposure and the development of melanoma and non-melanoma skin cancer (basal and squamous cell carcinoma). Children spend a lot of time outdoors and there is compelling evidence that childhood is an especially vulnerable time for the damaging (carcinogenic) effects of the sun.  The negative effects of UV radiation are accumulated during an entire lifetime and the risk of skin cancer increases with age. It is estimated that approximately 25 percent of our total sun exposure is acquired by age 18, and men over age 40, who spend the most time outdoors, get the highest annual doses of UV rays.   There is epidemiologic evidence supporting the causal relationship between sun exposure and skin cancer which includes a higher incidence of malignant melanoma in persons with a history of sunburns during childhood and adolescence; increased frequency of skin cancers with higher sun-exposure history; heightened risk of melanoma for those with increased childhood sun-exposure history; and relationship between sun exposure and increasing number of nevi, which may predispose to melanoma. The anatomic areas that skin cancer develops on appear to be somewhat related to the average amounts of UV exposure to those sites. For example, melanoma tends to be found more frequently on the legs in women, and the back in men. However, there is a trend toward increasing rates of melanoma on the trunk of women, due in part to clothing styles with increased skin exposure, opportunities for leisure activities in sunny areas and indoor tanning.

With increased life expectancies, and spending more leisure time outdoors, preventing ongoing accumulation of sun damage needs to be incorporated as an important part of a healthy lifestyle. Just as we try to limit our children’s exposure to other known carcinogens such as cigarette smoke, we should do everything we can to minimize their exposure to the ultraviolet radiation from the sun.

With the incidence of skin cancer on the rise, now is the time to take action against the ONE AND ONLY modifiable risk factor : excessive sun exposure. The purpose of sun-safety behavior is not to avoid outdoor activities, but rather to protect the skin from the detrimental sun effects. There are important steps you can take to decrease your risk of skin cancer without compromising the fun, or the competitive edge of any sport in which you may be competing.

Sun safety requires implementing a comprehensive set of sun safe behaviors, because no behavior alone will provide sufficient sun protection. While complete sun avoidance is not realistic, seeking shade when possible and capitalizing on the fluctuation of the intensity of UVB rays, by exercising outdoors in the early morning and late afternoon/early evening is recommended. The UVA rays will remain intense throughout the day, therefore the detrimental effects of the sun still exists at these times as does the risk of sunburn.  Additional sun protective measures include use of sunscreen. Sunscreens are chemical agents that help prevent the sun’s UV radiation from reaching the skin.  As UV radiation is comprised of both UVB (sunburn) and UVA (photoaging) rays it is important to use a product that protects against both types of rays, designated as “Broad spectrum.”  Sunscreens are designated by their SPF –Sun Protection Factor- which is a measure of a sunscreen’s ability to prevent UVB from damaging the skin. An example of how this works is as follows: If it takes 20 minutes for your unprotected skin to begin turning red, using an SPF 15 sunscreen should prevent reddening 15 times longer which is about 5 hours. It is estimated that sunscreens with SPF 15 block approximately 93 percent of all incoming UVB rays. SPF 30 blocks approximately 97 percent; and SPF 50 blocks approximately 98 percent.  Although these may seem like minor differences; for those individuals who are sunlight sensitive or who have a history of skin cancer, these extra percentages will make a difference. It is also important to note that no sunscreen can block 100 percent of UVB rays, and we do not currently have an established metric to calculate protection against UVA rays. So while “reddening” of the skin is an indication of your reaction to UVB rays, there is no immediate telltale sign of the UVA damage you may be accumulating.

Although moisturizers and after-shaves with SPF15 or higher may be sufficient for everyday activities where you spend a few minutes intermittently in the sun, stronger water-resistant sunscreens are required for aquatic sports participants as well as the spectators spending hours outdoors.  Currently in the US, many of the sunscreens available combine different active chemical sunscreen ingredients in order to provide broad-spectrum protection. Typically, at least three ingredients are combined to achieve this goal including PABA derivatives, salicylates, and/or cinnamates for UVB absorption; benzophenones (for example Oxybenzone and sulisobenzone) for shorter-wavelength UVA protection; and avobenzone (Parson 1789), ecamsule (Mexoryl), titanium dioxide, or zinc oxide for the remaining UVA spectrum. For individuals with sensitive skin, sunscreens composed of only titanium dioxide and zinc oxide are available. These latter ingredients are referred to as “physical blockers” as they function by reflecting the UV rays rather than absorbing and subsequently dispersing them like  “chemical blockers”  such as Parsol 1789, (which can irritate the skin in some individuals) .  The level of protection against UV rays is comparable between the physical and chemical blockers. To ensure that you get the full SPF of a sunscreen, however, you must apply a sufficient amount, which is 1 ounce-about a shot glass full.  Most people only apply half to a quarter of this amount, which translates to a lower SPF on the body than advertised on the sunscreen label. A good example for a long day in the sun that lasts hypothetically 8 hours would require the use of 4 ounces of sunscreen, or half of an 8 ounce bottle for just one person. Another significant factor in ensuring sun protection is when sunscreen is applied. Sunscreens should be applied 30 minutes prior to sun exposure to allow the ingredients to fully bind to the skin. Despite sunscreens being labeled as “water-resistant” and “waterproof”, they are only effective up to two hours and therefore require reapplication of the same amount every two hours. Sunscreens should also be reapplied immediately after swimming and toweling off.

We know that sunscreen alone cannot fully protect you from the damaging UV rays and risk of skin cancer. Although reapplication of sunscreen every two hours is recommended, it is not always feasible. Therefore, there are additional sun safe practices that should be adopted. Clothing is the single most effective form of sun protection as it is our first line of defense against the sun’s damaging ultraviolet rays.  Wearing sunglasses and wide-brimmed hats with at least a 3 inch brim will help protect your eyes, head and neck is prudent. For the rest of your body, there are several factors to consider when choosing the ideal attire for sun safety, and one of these is UPF, which stands for Ultraviolet Protection Factor. UPF measures the amount of UV radiation that penetrates the fabric and reaches your skin.  For example, a fabric with a rating of UPF50 will only allow 1/50th of the sun’s UV rays to pass through which means the fabric will significantly reduce your skin’s exposure to harmful UV radiation because only 2 percent of the UV rays will get through. When choosing clothing for every day wear, heavier weight and tightly woven or closely knitted fabrics (corduroy,denim,wool) , as well as synthetic  and semi-synthetic fabrics (such as polyester and rayon) offer the greatest sun protection . Dark and bright colors offer greater UVR protection than whites or pastels. A good rule to remember is that if you hold up fabric to the light and you can see through it, then UV radiation can penetrate it …as well as your skin. Also when clothing gets wet or excessively stretched, the UPF will go down. On a positive note, there are easy ways to increase the UPF of everyday by washing your clothing with a laundry additive such as Rit Sun GuardTM. This product has the active ingredient TinosorbTM which increases clothes sun protective abilities for up to 20 washings. It changes your everyday white cotton shirt from a UPF of 7 to 30.

For aquatic activities, choosing swim suits and rashguards that have been specially treated with chemical UV absorbers, known as colorless dyes are preferable. There are currently national criteria as well as international standards for UPF testing; a UPF label may state that the item meets the standards of the American Society for Testing and Materials and/or the AS/NZS Standard. In addition, choosing swimsuits with the greatest body coverage is paramount to protecting the skin from the harmful UV rays, especially during long practices and endurance events where reapplication of sunscreen is not feasible. Swimsuits with full back coverage and leg coverage either to the knee or ankle will help ensure more comprehensive protection. If such swimsuits are not readily available, wearing a rashguard over your swimsuit will be a useful substitute.

Key points:

  1. Sun safety should be incorporated into your everyday life as the sun’s harmful UV rays are present 365 days a year
  2. Wear broad spectrum sunscreen everyday: for daily activities a moisturizer or after-shave lotion with SPF15 or higher is sufficient; but for aquatic activities or prolonged outdoor exposure choose SPF 30 or higher; apply 30 minutes prior to exposure and reapply every 2 hours
  3. Wear sunglasses, a wide-brimmed hat (brim at least 3 inches) and choose clothing that is tightly woven, closely knit and dark or bright-colored. UPF labeled clothing is available or you can increase your own clothing’s UPF by using a product like Rit Sun GuardTM
  4. Seek the shade, but be aware that sunlight may reflect off surfaces like concrete ,water and sand and can reach you beneath an umbrella or tree
  5.  Avoid activities during peek sun exposure  hours between 10am and 4pm
  6. Healthy habits are best learned at a young age, therefore practicing sun safety for your children should be a priority. Damage from UV rays occurs with each unprotected exposure and accumulates over the course of a lifetime, therefore people of all ages need to be safe in the sun to minimize their risks of melanoma and non-melanoma skin cancer.

Acknowledgements:

This post is a modification of an article I wrote for a publication for FINA, the international governing board for all competitive aquatic sports.

Many of the facts used in this post were obtained from the Skin Cancer Foundation website:
http://www.skincancer.org

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