THE LABEL SPF CANNOT BE USED TO ESTIMATE SAFE SUN EXPOSURE TIME

How SPF Testing Fails to Replicate Real Sunlight and its Impact on Your Health

North American consumers should not rely on label claims - whether it is the SPF or claims of UVA and Broad spectrum protection. Most of our brand name sunscreens would not pass European or Australian criteria for UVA-PF (UVA- Protection Factor) and their better standards for Broad Spectrum coverage. Proper and adequate UVA protection may be the most essential property for a sunscreen to actually prevent skin cancer and photoaging. The global market, particularly in North America is dominated by UVB- BIASED sunscreens with inadequate UVA protection, despite label claims saying ‘BROAD SPECTRUM’ UVA/UVB. Even the EWG (Environmental Working Group) recognizes this reality in their 2017 Sunscreen Report. More on this in my next BLOG. 

There are over 25 stakeholder and professional coalitions with Comprehensive Cancer Control (CCC) plans  that publicise a prevention strategy. Language may differ but they all focus on key elements of sun avoidance, never burn or tan from UV exposure, wearing protective clothing with a tight weave, wear UV protective sunglasses, and generously apply a sunscreen with sun protection factor (SPF) 15 or higher and both UVA/UVB protection. Sunscreen use is the weakest link in the protocol. Rising cancer rates show that the current approach has failed and critical analysis argues that ineffective UVB-BIASED sunscreens dominating the N.American market are a driving factor.  Australia where balanced sunscreens using better UVA filters are plenty,  are actually seeing skin cancer rates levelling off or falling in certain provinces. Two landmark studies from Australia show that effective sunscreens applied daily can potentially reduce all forms of skin cancer. In N. America the grim reality is otherwise:

• Skin cancer is now the most common cancer in the United States with the incidence essentially doubling for all skin cancers in 40 years,  and they now account for more than 50% of all human cancers - i.e. skin cancer cases outnumber all other cancers combined. 

• In 2017, over 160,000 Americans are expected to be diagnosed with melanoma, which is the leading cause of cancer death in women ages 25-30 and the second leading cause in women ages 30-35.  In ages 15-29, melanoma is the second most commonly diagnosed cancer. From 1970 to 2009, the incidence of melanoma increased by 8-fold among young women and 4-fold among young men. In the USA, one person dies of melanoma every 54 minutes (almost 10,000/year).  4000 Americans die in a year from Squamous Cell Cancer (SCC) .

Preventing sunburn (early effect) or UVA damage (early and late effects), and damage to the genetic and immune apparatus of the skin is the essence of effective photoprotection. The label SPF is supposed to quantify a sunscreen’s ability to prevent that early sign of sun damage. The SPF as measured by FDA and Health Canada mandated tests give a poor estimate of the sunscreen’s actual performance in sunlight. 

The premise that SPF can be used to plan your exposure time is based on several invalid assumptions. Recent studies confirm that the lab or label SPF is inaccurate, when compared to the real life value obtained in sunlight. The lamp used in calculations for label purposes, only emits 290-400 nm based on the false assumption that the erythema reaction was mediated only by UVR (UVB and UVA). Visible Light (VL at 400-740 nm)) and Infra-red (IR at beyond 740 nm)) could be responsible for up to 20-30 % of the erythema response. Sunlight has more UVA (up to  5X ) than the testing lamp emission. Industry and physicians continue to advise consumers that the SPF can be used to calculate the safe exposure time for protected skin outdoors. We know differently -  fair individuals mostly get sunburned with prolonged outdoor exposure or during tropical vacations, despite using high SPF sunscreens and stringently following all the re-application instructions.   Media reports in 2015-2017 from Consumer Reports, the BBC in the UK, CBS, NBC, and CNN in the USA, have all presented data that up to 50% of brand name sunscreens fail to achieve even 50% of their labelled SPF values. 

Science now confirms this travesty. The label SPF is inaccurate when compared to the real life value obtained in sunlight. A landmark study  presented at the 26th Annual Meeting of The Photomedicine Society (Orlando, Florida, February 2017), showed that  50 commercially available sunscreens with label SPF 50 or more had SPF values of 6-10  when measured in sunlight (Hughes S. and  Cole C.). No wonder, as testing lamp emission spectrum is far removed from that of actual terrestrial radiation, and the intensity used in testing is different from sunlight. The compliance factor also adds another real life problem as most  users apply < than the 2 mg/cm²  as done for the lab test. Scientists also now provide the principles in physics that explain why the SPF test cannot be accurate (Diffey B, Osterwalder U, 2017).  They report that labelled SPF, determined by in vivo assay using a UV solar simulator, overestimates the SPF that would be expected in natural sunlight.  Products labelled SPF50+ may not be able to achieve a protection against sunlight of more than 25-fold., or SPF 25. The popular interpretation of the SPF to mean how much longer skin covered with sunscreen takes to burn in sunlight compared with unprotected skin, can no longer be defended.

Any falsely high SPF reading can be further  manipulated by adding anti-redness agents (similar to aspirin) that artificially increases the MED (Minimal Erythema Dose) used to determine the SPF, for the sunscreen containing these anti-inflammatory chemicals. Sunscreens are replete with SPF boosters- bisabolol, niacinamide, salicylate compounds, and numerous others. This may be very harmful to a consumer. The false (often high SPF 50-100) values distort the reality of what protection to expect. If you are very fair – Type 1- always burns never tans- you may actually burn within 5 minutes with extreme sun exposure. An SPF 30 conveys the impression that it is safe to stay out for up to 150 minutes and SPF 50 for up to 250 minutes. A real life SPF 10 in sunlight means you should multiply your 5 minute burn time by only 10 for a safe 50 minute exposure, then get out the sun or re-apply your sunscreen liberally if you stay out longer. A boosted SPF is falsely elevated by interfering with the biologic endpoint or early warning signal of redness, the first sign of sunburn. It is no longer commensurate to the amount of radiation being prevented from reaching your skin,  but related to delayed redness. You are actually burning but have no way of knowing this as your early warning signal has been blunted. This false sense of security may make you remain outdoors i/o seeking shade. You will experience more sun damage and incur the risks of skin cancer and photoaging. This  is only related to UVB exposure - think of the damage resulting from the more harmful UVA radiation that you are now receiving in high levels, particularly since most N. American sunscreens have inadequate UVA-PF values.

• Use no more than half the label  SPF when calculating your outdoor exposure time, and if you are redhead or extremely fair use a factor of 10.
• It is better to use the other elements of a photoprotection strategy – avoid sun exposure, wear UV protective clothing, wear head gear and UV protective sunglasses etc. - to the extent you can, and use a sunscreen with a safe UVA filter like zinc oxide in adequate concentrations.
• The particle type sunscreens that use zinc oxide, titanium dioxide, encapsulated octinoxate, drometrizole trisiloxane (Mexoryl XL™), terephthalylidene dicamphor sulfonic acid (Ecamsule or Mexoryl SX™),  biscotrizole (MBBT or Tinosorb M™), bemotrizinol (BEMT or Tinosorb S™),  and others are large in size, sit on the skin avoiding any entry into blood and the various attendant risks. Only the first five are available in Canada. Mexoryl XL™ and SX™ are patented to L’Oreal and regrettably are usually combined with undesirable soluble hydrocarbon filters, which should be stringently avoided. All except titanium dioxide and encapsulated octinoxate are UVA filters, and when mixed with other safe UVB filters achieve dispersions of spectral homeostasis (balanced UVA/UVB protection). In this situation where a sunscreen behaves like a neutral density filter, the label SPF may be closer to the Real Life SPF value in sunlight.  Look for products that have > 20% zinc oxide alone, or 15 % with 7.5% titanium dioxide or encapsulated octinoxate. 
• For maximum protection and to avoid all the controversy on hormone disruption and environmental hazards, use only sunscreens  with particle based or large molecular weight filters in the right combination. The high UVA protection achieves that flat balanced protection where the ratio UVA-PF/SPF approaches 1, and the label SPF comes closer to the Real Life value in sunlight. Strictly avoid all small molecular weight soluble hydrocarbon filters – avobenzone, oxybenzone, homosalate, octisalate, octocrylene, regular octinoxate, and 4-methylbenzilidene camphor. All may enter blood and only avobenzone has any UVA attenuation. It still gives a significant UVB bias where up to 30% of UVA between 340-400 nm – the most damaging UV rays are transmitted to your skin.

© Denis K. Dudley MD, October 2017. All rights reserved.

Can Using a Sunscreen Be Worse than Using a Tanning Bed? The Health Implications of a UVB Biased Sunscreen.

The New Study that Shows How a UVB Sunscreen Can Be Worse than a Tanning Bed

The Role of Long Wave UVA in Skin Cancer

There is an unrelenting rise in skin cancer rates in North America with an annual increase around 2-3 % over the past 3 decades. In the UK there was an alarming increase of 40% in the past 4 years. Empirical analysis of global skin cancer rates suggest that rates are levelling off or decreasing in countries with higher UVA-Protection Factor (UVA-PF) levels in sunscreens (2015 Sunscreen Symposium, Florida, September 2015). The compelling evidence for the primary role of UVA - particularly the UVA1 or longwave UVA -  in the genesis of skin cancer – comes from a number of scientific studies over the past 15 years (Halliday 2002, Agar 2004, Noonan 2012, Rünger 2012). This is logical and intuitive as UVA is more abundant than UVB and penetrates deeper into the skin.

The primary objectives of photoprotection  must be to prevent rising rates for skin cancer, reduce health care expenditures for a disease with potentially preventable aspects, and to reduce other effects of UV radiation, like photoaging and immune suppression. The continual 2-3% annual rise in skin cancer rates for North America shows that the current approach has failed. Critical analysis argues that ineffective UVB biased sunscreens are an important contributory factor. Cancer prevention and immune protection  from sunscreens in humans is dependent on protection from UVA and cannot be predicted from the SPF (sun protection factor), more a measure of UVB attenuation.

There is  a logical and evidence-based argument that the exclusive use of balanced sunscreens, which provide spectral homeostasis or uniform protection at every wavelength can reduce cancer rates and photoaging. The current  science confirms that UVB causes direct DNA damage, whereas UVA results in direct DNA damage and indirect effects from ROS (reactive oxygen species), photoimmunosuppression, and disruption of repair mechanisms.  UVB initiates and modulates the damage cycle but UV (particularly UVA1) completes the process. Photoprotection with traditional UVB biased sunscreens with little or no UVA protection must now be abandoned and a new clinical strategy adopted by doctors and as a public health policy.

How Can A UVB Biased Sunscreen Do More Harm than Good?

There is another powerful bit of evidence that implicates the widespread use of UVB-biased sunscreens, with little or no UVA1 protection, in rising skin cancer rates and visible photoaging at younger ages. Daily use of UVB biased sunscreens that dominate the market, exposes the patient to asymmetric UVA1 radiation, similar to a tanning bed. More people develop skin cancer because of tanning than develop lung cancer because of smoking. One indoor UV tanning session increases users’ risk of developing squamous cell carcinoma by 67 percent and basal cell carcinoma by 29 percent. People who first use a tanning bed before age 35 increase their risk for melanoma by 75 percent.  

There is an important  parallel between the asymmetric UVA1 from tanning bed exposure and using a UVB-biased sunscreen, either on vacation or every day. This crucial fact escapes our regulators, most physicians including dermatologists, and the cosmetic industry. 

Vacation exposure over 2 weeks with typical sunscreens for protection could be double the radiation received from 10  eight minute tanning bed exposures. In extreme cases of recreational sun exposure where sunscreens providing suboptimal broad-spectrum protection are used, the UV insult to the skin is likely to result in higher cumulative exposures than commonly employed sunbed practices (Diffey et al).

This occurred to me several years ago but the science and physics was beyond my capability. I kept asking Uli Osterwalder- one of the authors in the study and a friend- about this obvious concern, until they finally did the calculations. It is a computer derived analysis that suggests the wrong sunscreen - UVB-biased - may be more dangerous than tanning bed exposure. Both provide asymmetric UVA radiation to your skin. There is another cautionary aspect to this. The vacation model is more acute and intense but what about everyday exposure if using a UVB-biased sunscreen? Many outdoor occupations reach or exceed the vacation exposure.

If tanning beds cause higher risks for skin cancer, then providing a patient with a UVB biased sunscreen that gives a similar UV radiation profile, relative to the right conditions of exposure and time, should also be considered as an undesirable measure. For doctors involved with rejuvenation, prescribing a balanced sunscreen that gives adequate UVA1 protection is a responsible practice standard. This is an integral part of post treatment care after rejuvenation procedures. Without balanced protection, the patient resumes accelerated photoaging from UVA1 exposure and the  treatment benefit is quickly lost. Repeat treatments will then be required more quickly. 

What Is A Better Alternative?

Adequate but safe UVA1 protection is only attainable with filters like zinc oxide (>20%), zinc oxide (>15%) plus 7.5% titanium dioxide or encapsulated octinoxate, bemotrizinol, and bisoctrizole – insoluble particle type filters with no entry into our bodies. Regrettably,  the last two safe and highly effective insoluble particle filters, have yet to be approved by Health Canada and the FDA, despite their global use in every other country over the past 15 years.

Most UVB-biased sunscreens use the soluble filters that penetrate skin into blood and even tissues like receptors in the brain. The group includes oxybenzone (benzophenone), homosalate, octisalate, octocrylene, non-encapsulated or regular octinoxate, and 4-methyl benzilidene camphor. They are more active in UVB and shortwave UVA (UVA2). Some UVA1 activity comes from avobenzone, another soluble filter that obtains tissue levels. It enters the body and is unstable in sunlight. Most parents and pregnant women are unaware that these filters (used in over 80% of our sunscreens) gain entry to our bodies, reason enough to avoid them.

There is a principle in endocrinology – isoform function – whereby chemicals with the same structure likely bind to the same hormone receptor and generally have the same effects. Hence avobenzone and octisalate very likely exert the same toxic effects as oxybenzone and homosalate, known to be hormone disruptors. Oxybenzone and its structural cousin avobenzone are now the leading causes of photocontact allergy (Warshaw 2012). A 2015 report (Downs et al) confirms other studies over the past decade that oxybenzone washing of sea-bathers is genotoxic, kills larvae of reproducing coral, and converts the planula from a motile to a sessile state by ossification. Oxybenzone found in 65% of our poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.

Recommendations for Practitioners and Consumers:

You are faced with a simple choice in selecting a safe and effective sunscreen:

·       UVB- biased products with tiny soluble organic filters that give incomplete protection (inadequate UVA1 protection) and are implicated with adverse effects on our health and the environment. They are likely a root cause of rising cancer rates and early photoaging.

·       A balanced or truly broad spectrum sunscreen using insoluble filters, large particles that remain on the skin, have no known adverse effects on human health or the environment, and give you better protection, where the right combination can approach that of textiles and staying out of the sun.

·      Balanced sunscreens using insoluble particle type UV filters with no entry into blood of mother or fetus are safe to use in pregnancy. More egregious to me, is the fact that nearly all physicians fail to advise pregnant women and parents about percutaneous absorption of soluble filters and their possible hormone disrupting and carcinogenic effects. As a former obstetrician, I appreciate the persuasive simplicity that anything safe to use in pregnancy is safe to use for everyone.

The Latest Science in Sunscreens and Protection: What You Need To Know

For this third post, I thought I would pass on interesting and relevant scientific news from recent meetings I attended with my wife, Dr. Sharyn Laughlin. The Annual Meeting of the Photomedicine Society and the Annual Meeting of The American Academy of Dermatology were held in March 2014.

More evidence was presented by Dr. Thomas Ruenger for the role of UVA in inducing enzymes that promote the breakdown of collagen and elastin as an important mechanism for photoaging. The findings presented also show that the effect of longwave UVA is the most pronounced and much greater than the effect of UVB. Over the past decade, there has been a volume of evidence from scientific studies that confirm the important effect that UVA has on photoaging and the induction of cellular damage, leading to all forms of skin cancer. This should come as no surprise to anyone – including those who still do not acknowledge the inherent dangers of UVB-biased sunscreens that give unbalanced protection, and allow the effects of UVA to be mostly unabated and cumulative.

Our Skin: A Work of Art Worth Saving

Not everything in science needs a study. Many definitive studies cannot be done in humans for ethical and practical reasons. Sometimes critical thinking, cognitive analysis, deductive reasoning – fancy terms for common sense – is all that is required. UVA penetrates to the deeper dermis where the important elements regulating genetics, immunity, and cell function reside, while UVB barely penetrates through the epidermis. UVA is ubiquitous, essentially the same at any latitude and time of day, and is 15-16 times more potent than the dose of UVB that only accounts for 5% of the UV band. It should be logical that the adverse effects of UV radiation may have more to do with UVA than UVB. Erythema or redness of the skin, the first sign of sunburn, and the eventual sunburn, is commonly believed by many people (even some physicians), to be UVB (290-320 nm) mediated skin damage, with a minor contribution from UVA-2 (320-340 nm). It is the basis of the sun protection factor (SPF) that is a label standard that indicates the degree to which a sunscreen reduces the sunburn reaction. The new labelling rules to be adopted in N. America changes the meaning of SPF to denote sunburn protection factor, a more accurate definition. It should convey to the consumer that SPF is a measure of the sunscreen’s ability to reduce or protect from sunburn but is not an adequate measure of protection to other adverse effects of the sun. The erythema-sunburn reaction and its genesis is actually more complex and is also related to UVA-1 effects.

Anyone who has had a sunburn by not applying a sunscreen on a very cloudy day has experienced a UVA sunburn. It is a deeper burn and much more painful that the usual sunburn that starts with UVB initiation. A sunscreen that completely blocks only UVB will not always prevent sunburn and over time a gradual or delayed sunburn develops to the UVA part of the sun. UVB is more efficient in causing sunburn and produces the immediate redness. UVA accounts for 95% of UV exposure and this higher absolute amount contributes to erythema. The early or mainly UVB initiated sunburn reaction, is a protective response telling you to get out the sun when the damage is early and more superficial. Continued sun exposure, even with a sunscreen of high SPF, but minimal UVA-1 protection, eventually leads to a more severe sunburn and the deeper damage that causes irreversible consequences- photoaging and the DNA changes that may lead to cancer many years down the road. SPF values > 15 can only be attained if the UV filters used are reducing transmission of UVA-2 and UVA-1, but is primarily a measure of UVB attenuation.

Industry consultants continue to push the trend arguing for high SPF sunscreens with values > 50 even approaching 100. There is a minor photometric basis for using a higher SPF. Looking at the transmission, rather than what is blocked does show that SPF 30 gives twice the protection than SPF 15, a SPF 60 twice that of SPF 30 and four times SPF 15. An SPF 15 blocks 93.3% of incident UV compared to 96.6% with SPF 30, a difference of 3.3% for doubling the concentration of filters. However, considering what gets through by counting photons of light shows that only half the amount gets through with the higher SPF. The higher SPF also compensates for the lower application amounts used by consumers in practice than the amount applied for laboratory SPF testing. There is some truth in a consumer thinking that a higher SPF allows you better protection and a SPF 30 allows you to stay out twice as long as a SPF 15. The danger is that the higher SPF will have some UVA protection but not nearly enough, if it does not contain one of the limited number of filters that give adequate UVA-1 protection. I am cynical enough to think that industry pushes high SPF sunscreens knowing that the public assumes they are better in every respect. Given a choice between a SPF 30 and a SPF 50, always select the more balanced sunscreen with better UVA-1 protection. This is easy to do in the UK or Europe. Look for Boots 4 or 5 stars in the UK or a UVA-PF to SPF ratio of > 1/3 in Europe. The more this ratio approaches 1, the better the sunscreen is for affording you balanced and proper protection. North American consumers have no such ability  to use the label metrics for selection. The new rule of using a Critical Wavelength (CW) of 370 nm or greater as proof of truly broad spectrum activity, particularly the most important UVA-1 extinction, will not necessarily be valid.

The CW is a measure of the wavelength at which 90% of the area under the absorption or extinction curve occurs. This relates to broad spectrum activity as to achieve this CW of 370 nm, usually requires a significant UVA absorbance. However, the threshold of 370 nm can be attained by some sunscreens with little overall UVA-PF, particularly in the more problematic UVA-I spectrum approaching 400 nm. Sunscreens with low UVA-PF  and those with moderate UVA-PF can both have the same CW of 370 nm. The shape of the extinction curve is a factor and a UVB biased sunscreen SPF 30, with inadequate or a low UVA-PF  < 10 can attain the same CW of 370 nm as a sunscreen with UVA-PF of ≥ 10. One would fail the EU criteria but both would pass in the USA and Canada, under new regulations being enforced this year. My preference for adequate UVA protection is that SPF 30 values should have a UVA-PF exceeding 20 with the ratio approaching 1. More about these considerations in a later post.

The other important topics discussed at these meetings included the use of anti-inflammatory(AI) agents

Can a diet rich in anti-oxidants protect you from the sun?

or antioxidants (AO) in sunscreens, and the role for oral photoprotection as a component of a sun protection strategy. The use of AI ingredients will be discussed in detail in a future post. Dr. Salvador Gonzales  reviewed the present status of oral nutrients that afford some measure of UV protection, and its use in oral photoprotection is increasing in Europe at an annual rate of about 5%. He also reminded us that a lifetime UV radiation exposure is attained 1/3 through vacation, compared to 2/3 from every day or non-vacational time. This supports our view that a balanced sunscreen is for daily use all year round. In addition 70-80% of sunburns occur can occur in your backyard. Dr. Mary Matsui presented evidence that certain nutrient and botanical ingredients applied on the skin are a source of non-sunscreen photoprotection. The list of useful agents for oral or topical photoprotection is extensive. Some of these and other agents also may reduce skin damage from visible light (400-770 nm) and near infrared (IRA at 770 -1400 nm), now shown to be relevant in addition to UV in the genesis of adverse effects from sunlight. This an area I am presently researching at CyberDERM. While developing a balanced sunscreen that mimics the UV protection afforded by black clothing or shade, we are identifying the single best antioxidant to add to the formula. Some of the effects of UV and IRA on inducing immune suppression may also be reduced by oral therapy. Longer wavelengths UVA-1 near 400 nm and visible through IRA at 400- 1400 nm, tend to produce deeper damage to the dermis. Oral antioxidants may be more rational and efficient than topical application. The concept of skin therapy from within via the dermal blood vessels is not new. I recall an ad-campaign from many years ago- “have you taken your skin care today”? For therapy to cell damage in the dermis, ingestion and delivery by the dermal blood supply seems more logical than topical administration, which requires absorption through the epidermis, and the agent is not always sure to reach the deep dermis. We are also working on an antioxidant mix for oral supplementation that best achieves all the objectives. For now it appears that taking 2 Gms. of Vitamin C and 1200 IU of Vitamin C increases the minimal erythema dose –  the visible sign of sun damage – by 20% after 1 week and 40% at 3 months (Gonzales et al). Flavonoids and the subgroups- anthocyandins, catechins, flavonols, and isoflavones – all play important roles in modulating and inhibiting the various adverse effects. A diet rich in blue and red berries, red or purple grapes, 1-2 glasses of red wine/day, dark chocolate, green and white teas, apples, broccoli, onions and scallions, kale, soybeans, hot peppers, apricots and celery, provides Flavonoids. This diet with Vitamin C and E as described above may be a useful adjunctive measure to using a balanced sunscreen and sun avoidance  for those at greater risk of cancer and photodamage. These nutrients, along with ingesting curcumin, resveratrol, and pomegranate, are already recommended for a myriad of health benefits. Skin cancer is considered an occupational disease in some provinces of Germany, and in Canada we need a National Occupational Strategy for those involved in outdoor work. For these workers and anyone at higher risk for skin cancer, a dietary approach as outlined is a complementary and responsible self- help initiative.

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:

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?

Figure 2: The Fitzpatrick Skin Type Classification

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.