Tuesday, 28 January 2014

THe Hierarchy of Sun Smart Behaviour

The first post dealt with rising skin cancer rates in N. America. Up to 4 million Americans and 120,000 Canadians will develop a skin cancer this year. One in six Canadians and one in five Americans will develop a skin cancer within their lifetime. More alarming, is the rising rate for all skin cancer but particularly the rate for melanoma.  The last post dealt with the public health and economic dimensions of the problem. Scarce health care resources are spent on a  preventable disease and costs continue to rise. In Canada up to 1/4 million cases of skin cancer could cost over one billion by 2030. Collectively, we need a new strategy. There is a need for new public health policy, but after years of trying to engage public officials, I have come to the conclusion that they are either unable or unwilling to frame effective solutions. Each of us must adopt our own public health measures and educate or encourage our entire circle of friends, relatives and contacts.

The Basics:
Sunscreen Doc-Why the Coppertone Philosophy does not work anymore.
Figure 1: The Iconic Coppertone Baby
Everyone can adopt a simple approach to sun safety motivated by wanting to lower your risk for skin cancer, to reduce photoaging and retain a younger appearance, or simply do it for public responsibility. First, an understanding of basic photobiology. Sunlight contains visible light at 400-760 nm and  ultraviolet (UV) at wavelengths 290-400 nm. Longer infra-red beyond 760 nm gives you the feeling of warmth on your skin and also has negative effects. However, most sun-damage comes from UV that accounts for 5% of total sunlight. Sunscreens are supposed to absorb, scatter, or reflect this entire range of invisible UV energy - UVB (290-320nm) and UVA (320-400nm), which is split into shortwave UVA (UVA-II at 320-340nm) and longwave UVA (UVA-I at 340-400nm). Most  Canadians will be using sunscreens that filter UVB and provide inadequate or no protection to harmful UVA radiation, particularly in the UVA-I band. UVA accounts for 95% of the UV radiation reaching a person and is 15 times more potent on earth than UVB. It is illogical for sunscreens to be UVB-biased, as they are in N.America, providing most protection against UVB. Sunscreens need to provide balanced protection aiming for equal attenuation at every wavelength. The word ‘balanced’ will be a recurring refrain in this series. Your ability to identify and use a sunscreen with balanced UV protection will be the ultimate part of a smart sun protection hierarchy. The iconic Coppertone ad (Figure1) shows the graphic profile of the UVB sunscreen that allowed tanning without burning – UVB biased. Newer sunscreens give some more UVA-II protection but the ideal and safest sunscreen would be balanced, depicted by the profile at the right- similar to the lady shaded by a parasol. This is defined as balanced protection or spectral homeostasis – where a sunscreen affords virtually equal protection at every wavelength across the entire UV spectrum from 290-400 nm.

What to do?

The Sunscreen Doc: The Fitzpatrick Skin Type Classification
Figure 2: The Fitzpatrick Skin Type Classification
Sunscreen Doc: Time to Burn Based on Skin Type
Figure 3: Time To Burn Based on Skin Type
The next step is to be aware of the harmful effects of UV radiation. All types of skin cancer can occur in areas never exposed to the sun, but the majority are related to effects of UV radiation. It is estimated sun damage causes 90% of non melanoma skin cancer and 65% of melanomas, and most are potentially preventable. Sunburn and the erythema effect (the visible warning sign of UV skin damage) is caused almost entirely by UVB and UVA-I (290-340nm). Figure 2 gives the classification dermatologists use and Figure 3 shows the time for unprotected skin to burn. Unprotected white skin (Type I) can show mild erythema and sunburn after 1-2 minutes under the tropical summer sun at noon.  UVA radiation may be more harmful than UVB with a wider scope of skin damage- immune suppression, accelerated photoaging, and skin cancer. UVA as a longer wavelength penetrates deeper than UVB.  20 times more UVA, particularly the deeper penetrating UVA-I, reaches fragile proliferating cells in the basal layer of the epidermis and harmful effects even extend below the dermis (Figure 4). UVB triggers the sunburn and tanning response. UVA that penetrates deeper and stimulates the melanin response in the dermis responsible for the deeper and longer lasting tan. That is why the early sunscreens were formulated to prevent sunburn but to allow tanning by being UVB-biased. They blocked UVB and inhibited sunburn but allowed harmful UVA rays to stimulate a tan in melanin-competent skin- usually Skin Types III-V.   Do not consider a tan as UV protection. It is a protective response that says damage to your skin has occurred. The role of harmful UVA rays in tanning is also the reason why dangerous tanning beds use pure UVA light. This ill-advised way to tan is linked to the dramatic rise in melanoma rates in younger patients, particularly females under 30.

Figure 4: Detrimental Effects of UV to Human Skin
What does it mean to be Sun Smart?

The hierarchy of Sun Smart or Sun Safety Campaigns begins with being aware of the UV-Index and linking your dress and sun-avoidance behaviour accordingly. See Figure 5&6, for what the index means and sensible measures you should adopt. We recommend a daily balanced sunscreen every day to exposed skin. The UVA band is ubiquitous- almost constant with time of day or at any latitude- 70-80% penetrates clouds or fog, and window or auto glass. UV radiation dose increases by 5% for every 1000’ rise in altitude.  Winter can actually be worse as snow can increase your exposure by 80% due to reflection by snow – as does sand and concrete. The UV Index is global but my informal study suggests that < 30% of Canadians know what it means and actively look for it every day. In contrast, 96% of Danes know what the UV-Index is and 89% know how to interpret it. Up to 50%% key the index to behaviour and decisions about sun-protection, particularly for children living at home. Our only added precaution is that even when the index is low, you should use a balanced sunscreen everyday to prevent UVA exposure that is difficult to limit any other way. A UVA burn is deep and painful as many who go sailing or recreate on cloudy days can confirm. It is harder to reduce your UVA exposure by just staying out of the sun. The best way is to add every morning use of a balanced sunscreen to sun avoidance measures (there is that word- balanced again). This will reduce your risk of skin cancer and retard photoaging by up to 25 years. Used from the teenage years this can mean that when you are 70 it is possible to look like you are 45. We recommend use of a daily balanced sunscreen with filters that do not enter the body, in every person over 6 months of age.

Figure 5: Deciphering the UV Index System

Choosing the best sunscreen:

We can now make balanced sunscreens that give as much UVA protection as UVB. I am presently working with scientists in Europe to make such a sunscreen that will mimic the protective effects of shade or black clothing. The benefits are exciting compared to the limitations and dangers of unbalanced UVB-biased sunscreens, with minimal UVA protection that now dominate the market in N. America. A few UV filters are able to achieve a balanced UVB to UVA protection approaching unity. These include zinc oxide, Tinosorb S™ and Tinosorb M™, and Mexoryl XL™, in tailored combinations. Interestingly, these filters also belong to a group of 7 filters with large molecules that do not enter the skin. This gives them the best safety profiles favored by consumer groups. Look for these agents in combination with each other or titanium dioxide, and no other active ingredients. Many products that use these agents add the other organic filters with small molecular weights that quickly penetrate your skin into blood and all your tissues. There are several potential dangers – links to cancers and hormone disruption and photoallergy. A prudent approach would be to avoid these risks and use filters that do not enter the body.

Figure 6: How Best To Protect Yourself

 Zinc oxide is the only single agent used in concentrations of 15% and over that gives adequate SPF values, and relatively balanced protection. New formulas can be very aesthetic and go on clear. Look for EWG preferred sunscreens such as our Simply Zinc Sun Whip, if you can pardon the plug but these are the concepts we used to formulate it. 

 The next post will deal with details of UV effects and the benefits of reducing your lifetime exposure. Later posts will show the differences in UVA protection between a balanced and a UVB biased sunscreen, and assist the reader in selecting a balanced product from among  the minority of those available in N. America.



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