UVA – The Sunscreen Doc

SUN PROTECTION MYTHS: FACTS VERSUS FICTION

INTRODUCTION

Media and “experts” continue to misinform consumers about sunscreens and UV protection. Facts need to be separated from fiction. This blog is dedicated to Nikiforos Kollias PhD (biophysicist, photobiologist, medical physicist, bioengineer, Professor of Dermatology at Harvard and UBC). He spent the last 20 years of his life trying to dispel the first myth – that there is a difference in the way “mineral or natural” and so called “chemical” sunscreens protect against UV radiation.

FICTION

The words “natural” versus “chemical” are used deceptively to imply that some sunscreens are not chemicals, and that a natural or mineral product might be preferable because it acts as a physical barrier that bends or reflects light, compared to chemical sunscreens that absorb light. This has misinformed the consumer since the last century. It is repeated ad nauseam by every “expert” like a recent CBC program hosted by Heather Hiscox, where another “expert” physician said “physical or barrier” sunscreens reflected or blocked UV radiation and “chemical” products absorbed harmful rays.

FACT

All sunscreens are CHEMICALS – fundamental Chemistry. A chemical is a substance in any form : ionic, molecular, organic or inorganic – that is generated by or utilized in a chemical process. Some are organic – meaning carbon based with complex carbon chains and rings in their structure. Mineral UV filters are inorganic compounds (contain no carbon atoms) like zinc oxide, titanium dioxide, iron oxide, and others. Their individual atoms all occur on the Table of Chemical Elements.

FICTION

The labels physical and chemical as applied to sunscreens are inappropriate (Professor N. Kollias, Archives in Dermatology, Feb 1999). Minerals like titanium dioxide (TiO₂), zinc oxide (ZnO), and others, remain as particles in a sunscreen because of low solubility. These substances are ‘physical’ since they have a predetermined particulate size but are chemicals by any definition. Even soluble organic filters will form physical crystals as the carrier base evaporates. Consumers are blitzed with the fallacy that “natural” (mineral) filters reflect or bend light like a barrier- whereas the so-called chemical agents absorb light in a chemical reaction.

FACTS

Photoprotection from scattering or reflection of light occurs only if a very thick optical barrier prevents light from passing through to the skin, similar to a thick coat of paint not seen in commercially available sunscreens. This would not be acceptable to any consumer. A thick mineral based make-up will achieve some reflection or a “barrier” effect but all sunscreens absorb photons of light in reducing sun damage.
The word chemical is a misnomer as ALL UV FILTERS ARE CHEMICALS. At The Sunscreen Company TM we condemn small Molecular Weight soluble organic filters that reach blood and tissue. Organic does not mean natural or safe – only carbon based. Many of these synthetic filters contain the 6-carbon benzene ring so inimical to humans and the environment. The mineral filters zinc oxide and titanium dioxide ARE STILL CHEMICALS – albeit inorganic – made by a geologic system (mother earth) – hence the tendency to think of them as natural. Mineral filters are now so processed, highly refined, milled, doped and coated that they are really “naturally derived” but so altered that they are semi-synthetic and hardly natural.
New and more efficient nanoscale mineral sunscreens < 1 micron in size only scatter < 10% of incident light. Even older pigment grade forms of zinc oxide and titanium dioxide with larger molecules over 1 micron in size did not reflect more than 15% of the UV rays. All mineral or insoluble UV filters act as semi-conductors and absorb photons with electron shifts to a different valence band, so a harmful wavelength is converted to a less harmful or innocuous wavelength. New particle type filters are synthetic organic compounds that are also insoluble.
The only accurate classification of UV filters is soluble versus insoluble and definitely not natural versus chemical. Both types mostly act by absorbing photons. The mechanism of action in mineral UV filters involves the use of photon energy to excite electrons. For example, rutile TiO₂, has a band gap energy of 3.06 eV corresponding to a wavelength of 412.5 nm. Light at or below this wavelength will have enough energy to excite electrons from the valence band to the conduction band. Any photon with a wavelength longer than the band gap will not be absorbed by the sunscreen. Each substance has its unique semiconductor properties and band gap, accounting for the filtering activity at different wavelengths.
Filters are safer and preferable not because of “natural” versus “chemical” but Insoluble filters like zinc oxide (inorganic) or bisoctrizole (organic) are safer since their large size prevents entry through skin into blood, avoiding all the issues with hormone disruption and adverse effects. They are not photocontact allergens like the soluble organic filters. The best UVA filters belong to this group and provide the broad spectrum protection and high UVA shielding required to prevent skin cancer and photoaging.

FICTION

Consumer Reports suggested recently that SPF retesting done by them shows which brand name sunscreens are better. They recommended as best products, several with soluble organic UV filters like avobenzone and oxybenzone, since their tests showed better agreement with the label value for SPF. The same report suggested that mineral based sunscreens like zinc oxide with or without titanium dioxide were not to be recommended as the retest SPF did not meet label claims. This is a dangerous recommendation as it may influence consumers not to use mineral sunscreens. In the right concentrations mineral products are the safest sunscreens for humans and the environment. Along with other new insoluble UV filters, mineral agents deliver better UVA protection required for truly BROAD SPECTRUM shielding to prevent sunburn, skin cancer, and photoaging.

FACTS

The laboratory SPF test with a solar lamp emitting a limited light spectrum compared to sunlight is useless in predicting how a sunscreen performs in Real Life sunlight for many reasons. Studies confirm products labelled SPF 50-100 tested in sunlight are actually SPF 10-15. Professor Brian Diffey – a physicist – showed that based on laws of biometrics and physics – most sunscreens cannot achieve a SPF above 25. FDA and Health Canada have been advised by scientists that SPF lab tests and others are accurate for lotion formulations using soluble organic filters, but are erroneous for products containing particulates like zinc oxide or titanium dioxide. The tests require modifications to accurately assess the true performance of these and other particulates. Ask any consumer if they have ever had a sunburn with mineral sunscreens using proper concentrations like 22-25% zinc oxide or 15-20% zinc oxide with a filter like titanium dioxide 7.5% or special particle dispersions. Yet 70% of fair skinned consumers may return from vacation with sunburn after applying high SPF brand name sunscreens using soluble organic filters, despite re-application every 2-3 hours and label claims of water resistance. The SPF is a fallacious test and bears no relation to outdoor performance in actual sunlight– repeating it in a different lab and comparing values just gives another useless result and cannot be used to assess the quality of a product.
This Consumer Report suggesting that the best sunscreens are those using soluble organic filters is untrue and detrimental to the consumer. The ability to prevent sunburn is one thing and the SPF may be a rough guide, but the prevention of skin cancer and photoaging depends on UVA shielding. The soluble small sized filters all enter your blood, including oxybenzone, just banned in Hawaii because of the toxicity to coral and marine wildlife leading to severe reef degradation. The entire group are suspected hormone disruptors and may be linked to some cancers like thyroid and prostate. Worse, they give UVB-BIASED protection where the sunscreen transmits 10 times or more UVA than UVB radiation. The UVA filter used in most sunscreens is avobenzone. It is not photostable, has a similar structure to the Hawaii banned oxybenzone – likely has similar effects – and at 3-4% in a SPF 30-50 sunscreen has a UVA-PF (UVA Protection Factor) < 10 , inadequate to prevent sun damage.
Proper protection approaching indoor shade and dense textiles comes from the degree of UVA protection – a UVA-PF > 10. Higher is better and high UVA shielding usually means high UVB as well, but not vice versa. Use zinc oxide in the right concentrations and in CLEAR particle dispersions for the best UVA and BROAD SPECTRUM protection available in N. America.

THE BEST SUNSCREENS TO PREVENT SKIN CANCER AND PHOTOAGING

Safety is the prudent first principle in selecting a sunscreen. Use ONLY combinations of these filters where available :

Zinc oxide, titanium dioxide, encapsulated octinoxate, ecamsule (Mexoryl SX™), bemotrizinol (Tinosorb S™), bisoctrizole (Tinosorb M™), polysilicone -15 (Parsol SLX™), iscotrizinol, octyl triazone, and bisdisulizole disodium (Neo Heliopan AP™). None are hormone disruptors and only octyl triazone is a photoallergen.
Avoid them if they are combined with “undesirables” – oxybenzone, avobenzone, homosalate, octisalate, octocrylene, regular octinoxate (not encapsulated), and 4-methyl benzylidene camphor – all small molecular weight filters that pass into blood, are suspected hormone disruptors, photocontact allergens, and likely degrade coral through hormone disruption.

Good filters like bemotrizinol, bisoctrizole, ecamsule, drometrizole, and bisdisulizole are of limited availability in Canada and the USA, and even abroad are usually combined with the “undesirables” and best avoided. Adequate filter levels is the second selection principle to ensure enough UVA protection and truly BROAD SPECTRUM protection. Zinc oxide is the only safe and effective UVA filter widely available in N. America. Look for 15-25% with or without UVB filters like encapsulated octinoxate or titanium dioxide. Any sunscreen with < 15% zinc oxide hardly achieves the UVA shielding needed to prevent skin cancer and photoaging. My next blog describes:

How to ensure your sunscreen has good UVA protection
Why high UVA shielding mimics ideal protection from indoor shade and tightly woven clothing.
Why high UVA shielding will prevent skin cancer and photoaging.
Why CyberDERM sunscreens provide the best UVA shielding in very transparent esthetic products with the best sensory feel on your skin.

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

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/cm²as 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.