Understanding Ultraviolet Radiation and the necessity of a quality Sunscreen
By acancerfreeutah on September 11, 2007
Since I wrote about Justice Roberts' stance on FDA regulations regarding sunscreen, I have received a variety of emails that indicate a general misunderstanding of sunscreens; how sunscreen works and why a quality broad-spectrum sunscreen is, in fact, a crucial part of savvy sun protection and reducing your risk for skin cancer.
So, here are some additional facts about sunscreens to reemphasize the the importance of regulating sunscreens; ensuring that manufacturers produce only the best, most effective sunscreens to provide optimum protection against ultraviolet radiation, and holding them accountable to the claims they make regarding the effectiveness of their sunscreen products.
Sunscreen Fact Sheet - Part II
FDA monograph and Australian sunscreen standard
(Note: The Australian standards on sunscreen efficacy are considered the strictest in the world. They require sunscreens have a minimum 5% zinc oxide and a minimum 5% titanium dioxide so as to reflect/deflect UVA and UVB rays from damaging your skin.)
What are sunscreens?
Sunscreens are products that protect the skin from damage caused by ultraviolet radiation (UVR). They do this by using organic chemicals that absorb light and dissipate it as heat, as well as inorganic filters (blockers) that sit on the surface of the skin and act as physical barriers; or a combination of both.
There are three types of UVR:
• UVB - primarily responsible for sunburn and suntan. Long-term exposure leads to premature aging of the skin and skin cancer.
• UVA - primarily responsible for premature aging and skin cancers like melanoma and basal cell carcinoma.
• UVC - is absorbed by the earth's atmosphere.
What protection do sunscreens provide?
SPF 30 sunscreens filter 97% of UVB rays. In Australia, broad-spectrum sunscreens must protect against 95% of UVA rays. In the United States, there is no approved evaluation of UVA protection, therefore "broad-spectrum" labeling is open to interpretation. Consumers should be educated on the ingredients that provide UVA protection. Products that contain 5% or more zinc oxide provide excellent UVA protection.
Key points about sunscreens:
• No sunscreen is entirely waterproof/sweatproof. Sunscreen should always be applied to dry skin. All sunscreens start to come off during activity, therefore it is important that sunscreen be reapplied after towel drying. Products labeled as "waterproof" in the United States have completed an 80-minute still-water bath test. Products labeled as "very water resistant" in Australia retain their SPF after 240 minutes in moving water. Australia does not allow the use of "waterproof" or "sweatproof," and the FDA has asked for voluntary removal of such labeling on sunscreens here. In reality, it should be a mandatory removal of such labeling because it misleads consumers! (Note: Blue Lizard sunscreen says "very water resistant" by Australian standards).
• No sunscreen provides "all-day protection." As stated previously, chemical absorbers work by absorbing light, but they can be photo (sun)unstable. For example, Avobenzone loses 36% of its effectiveness within the first 15 minutes of sun exposure. Inorganic filters (zinc oxide and titanium dioxide) adhere to the skin but can be removed during towel drying. Australia does not allow the use of "all-day protection." Moreover, the FDA has asked for voluntary removal of this label claim. This is why it is so important to reapply sunscreen. Not only does your skin, acting akin to a sponge, reach its saturation point after about two hours thus requiring another layer of sunscreen to be applied, reapplication helps maximize your sunscreen efficacy.
• High SPF sunscreens do not necessarily offer broader or better protection. SPF only indicates the amount of UVB protection a product provides and does not indicate how much if any UVA protection is provided. The consumer needs to understand that the specific formulation of the sunscreen determines the amount of protection provided. Zinc Oxide products (5% or higher) provide very photostable UVB and UVA protection. High SPF products (i.e. SPF 45, 55, 60) typically contain high levels of organic chemicals that can increase the potential for irritation and absorption, especially in children. Higher is not always better, which is why Australia limits SPF label claims to 30. If you consider that a SPF 20 is preventing 95 out of every 100 UV protons from penetrating your skin, than a SPF provides excellent protection. The American Academy of Dermatology recommends SPF 30.
• No sunscreen offers complete 100% protection against the sun. Therefore products using the term "sunblock" are a misnomer as they allow some UV to penetrate the skin. A product that contains zinc oxide does provide blocking (reflective) capabilities but even zinc oxide, unless applied as a paste, allows a little UV light to penetrate the skin.
With that, it is important to understand how ultraviolet radiation works so as to further illustrate the seriousness of UV exposure (especially from tanning), it's direct link to an increased risk for skin cancer (and the fact that skin cancer is the most common cancer in the world), hence the importance of sun safety and proper use of a quality SPF 30 sunscreen.
Furthermore, I have (with the help of the Environmental Protection Agency, the AAD, and ARPANZA and my good friend, Kathleen, a physicist at the University of Nova Scotia) compiled a list of common questions people ask about ultraviolet radiation, how it works, and its link to skin cancer:
Understanding Ultraviolet Radiation - Q&A
Q. What is solar ultraviolet radiation?
A. Ultraviolet radiation (UVR) is defined as the portion of the electromagnetic spectrum between 100 nanometers (nm) and 400nm. Ultraviolet radiation is classified by wavelength into three regions: UVA - Ultraviolet radiation in the range 315nm to 400nm is thought to contribute to premature aging and wrinkling of the skin and has recently been implicated as a cause of skin cancer. UVB - Ultraviolet radiation in the range 280nm to 315nm is more dangerous than UVA and has been implicated as the major cause of skin cancers, sun burns, and cataracts. UVC - Ultraviolet radiation in the range 100nm to 280nm is extremely dangerous but does not reach the earth’s surface due to absorption in the atmosphere by ozone.
Q. How are people exposed to UVR?
A. Solar UVR is the single most significant source of UVR and can reach a person on the ground from three sources, directly from the sun, scattered from the open sky and reflected from the environment. This means that even if a person is shaded from the direct sun they can still receive substantial UVR exposure from the open sky. Also some ground and building surfaces are quite reflective to UVR including white paint, concrete and metallic surfaces. These surfaces can reflect UVR onto the skin and eyes. Reflective surfaces can reduce the effect of protective measures. There are also many types of artificial UVR sources, some of which emit high levels of UVR. Arc welders used in industry produce an intense UVR emission and workers exposed to welding radiation may suffer similar health effects to workers with over exposure to solar UVR. There are many other forms of artificial UVR sources such as fluorescent lamps, mercury vapor, metal halide and quartz halogen lamps used in industry, offices and in the home.
Q. How is UVR measured?
A. Broadband UV biometers and pyranometers are generally used to measure or monitor solar UVR. These instruments measure global solar UVR received on a horizontal surface from the entire hemisphere of the sky. Solar radiation includes both UVR transmitted directly and scattered UVR from the atmosphere, so the design of these instruments ensures measurement of both direct and diffuse radiation. These instruments can also be used to monitor changes in ozone levels and cloud cover effects by measuring changes in UVR irradiation levels.
Q. What are the effects of exposure to UVR?
A. The major organs at risk from exposure to UVR are the skin and eyes as the penetration depth of UVR is very short. Ultraviolet radiation can be produced by various artificial sources but for most people the sun is the predominant source of UVR exposure. For outdoor workers without adequate protection or control measures the levels of solar UVR may exceed the generally accepted exposure limits. Those who have been over-exposed to UVR may be unaware of their injury as UVR cannot be seen or felt and does not produce an immediate reaction. Over-exposure to UVR can cause sunburn, skin damage and skin cancer. The most obvious short-term effect of over-exposure to UVR is sunburn. The more UVR exposure, the worse the sunburn becomes. A person’s cumulative exposure to UVR along with the number of severe sunburns they have received, especially during childhood, increases their risk of developing skin cancer. Sun exposure causes the outer layers of the skin to thicken and long-term exposure can cause skin to wrinkle, sag and become leathery. Melanoma, the least common of the skin cancers but the most dangerous, may be related to severe exposure to solar UVR at an early age. Malignant melanomas may appear without warning as a dark mole or a dark “spot” on the skin. UVR exposure also places our eyes at risk of photokeratitis, photoconjunctivitus, ocular melanoma, and cataracts. Cataracts is one of the most common types of eye damage in Australia. Cataracts is the clouding of the lens of the eye, which is responsible for focusing light and producing sharp images. Without intervention, cataracts can lead to blindness.
Q. How can I reduce my risk from UVR exposure?
A. Increasing public awareness and interest in UV protection is due in part to the requirements for occupational protection of outdoor workers as well as the provision of UVR protection for the recreational market. Behavior outdoors can significantly affect a person’s solar UVR exposure and use of items of personal protection can provide a substantial reduction in the UVR dose received. Many forms of personal protection are available to reduce a person’s exposure to solar UVR. The best protection is to avoid peak hours of 10:00 AM and 4:00 AM when the sun's rays are most intense, coupled with proper sun protection year-round (even on cloudy and cold days). When outdoors, wear sun protecting clothing with good body coverage (that is rated at UPF 30-50+), a wide-brimmed hat, UV protective sunglasses and a SPF 15+ sunscreen. Over recent years interest has extended to shade structures and the UVR protection offered by commonly used materials such as shadecloth, plastic roofing materials, glass and window tinting films, even specially manufactured sun protective clothing.
Q. What is the UV Index?
A. Some exposure to sunlight can be enjoyable; however, too much could be dangerous. Overexposure to the sun's ultraviolet (UV) radiation can cause immediate effects such as sunburn and long-term problems such as skin cancer and cataracts. The UV Index, which was developed by the National Weather Service and the U.S. Environmental Protection Agency (EPA), provides important information to help you plan your outdoor activities to prevent overexposure to the sun’s rays. The UV Index provides a daily forecast of the expected risk of overexposure to the sun. The Index predicts UV intensity levels on a scale of 1 to 11+, where low indicates a minimal risk of overexposure and 11+ means an extreme risk. Calculated on a next-day basis for every ZIP code across the United States, the UV Index takes into account clouds and other local conditions that affect the amount of UV radiation reaching the ground in different parts of the country.
UV Index Number Exposure Level
0 to 2 Low
3 to 5 Moderate
6 to 8 High
8 to 10 Very High
(Note: You can learn more about ultraviolet radiation and see graphics illustrating the aforementioned concepts in my book ONLY SKIN DEEP? An Essential Guide to Effective Skin Cancer Programs and Resources).
I will continue to address the issue of proper sunscreen usage, sun safety, tanning, and other proven-effective methods of skin cancer prevention. With 90-95% of skin cancers resulting from over-exposure to ultraviolet radiation from the sun and tanning, skin cancer is largely preventable. Yet, in order to prevent skin cancer we must take proactive measures to protect ourselves and youth from it. The media and society, as a whole, may not recognize the seriousness of skin cancer and how incidence is growing at epidemic rates; however, I will continue to do bring this issue to light in hopes to not only raise awareness but convince people to protect themselves. We have a responsibility to do what is necessary to protect ourselves and others from skin cancer, especially when we can largely PREVENT it. The first step is proper education about skin cancer prevention. And the first step in preventing skin cancer (or, at least, significantly reducing our risk) is protecting our skin from over-exposure to damaging, even carcinogenic (cancer-causing) ultraviolet radiation. In turn, one of the most effective methods of protecting our skin from UV exposure is proper year-round use of a quality sunscreen.
Summarily, I'm not saying that we must become hermits and avoid going outdoors. I was raised in Southern California, and now live in Utah -- two places that enjoy the sun and outdoors. (Incidentally, two places with high incidences of skin cancer). I am saying, however, that we must be smart and SAFE about the sun (and avoid tanning beds) by properly protecting our skin from ultraviolet radiation. Perhaps, it is easier said than done. Or, perhaps, we need to be willing to take the proper precautions; to see skin cancer as a real disease that can kill (just like any other cancer) and that we can, perhaps, save someone from having to die from it -- even ourselves.
Keep those questions, comments, and emails coming, folks. I enjoy hearing from you. It helps me be a better skin cancer educator; to know what topics to discuss on the Blog, how to develop effective educational messages and tools, and better serve both the skin cancer community, as a whole, and most especially - YOU.
Your SunSavvy friend and advocate,
Danielle & The Cancer Crusaders Organization
"I use sunscreen everyday and always recommend it to my patients."
- Dr. Roger Ceilley,Iowa dermatologist
and past president,American Academy of Dermatology
*FOR patient photos, informational links, more information, or to post comments, please visit my Blog at http://onlyskindeepbook.blogpspot.com.