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.
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.
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.
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.
- 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.
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.
- 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.
© Denis K. Dudley MD 2018. All Rights Reserved.