Zinc Oxide Sunscreen & Nanoparticles
Zinc oxide is a powdered mineral that sits on top of the skin, scattering and absorbing UVA & UVB rays.
We feel zinc oxide is the safest and most effective sunscreen. The best protection from the sun, however, is to seek shade and wear clothes and a hat.
All Badger sunscreens have pharmaceutical grade uncoated Non-Nano Zinc Oxide as the only active ingredient.
Badger uses uncoated non-nano zinc oxide as the only active ingredient in all our sunscreens. This is the same kind of zinc oxide used in calamine lotions and diaper rash creams.
What is zinc oxide and where does Badger's come from?
Zinc oxide is the metal zinc that has been oxidized. The chemical formula is ZnO, 1 zinc atom and 1 oxygen atom held together by an ionic bond. Zinc oxide does occur in nature as the mineral zincite, but it is quite rare and commercially unavailable. Badger's zinc oxide is manufactured using 100% clean recycled zinc left over from other processes, and purified via distillation into pharmaceutical grade zinc oxide.
Isn't zinc oxide just another chemical?
We've been asked: "Zinc oxide is technically a chemical so how can Badger call their sunscreens chemical-free?" According to one common definition of a chemical "a substance with a distinct molecular composition that is produced by or used in a chemical process" yes, zinc oxide (ZnO) could be considered a chemical, as could salt (NaCl), water (H2O), and sugar (C6H12O6). We follow a more sensible approach and we do not consider zinc oxide to be a chemical, especially when compared to other synthetic sunscreen ingredients that do not occur in nature, such as octocrylene (C24H27NO2) or benzophenone (C6H5)2CO. Zinc oxide is a powdered mineral that does not dissolve into or react with our sunscreen formulas and will not absorb into your skin.
What is a nanoparticle and what is non-nano?
A nanoparticle is a particle smaller than 100 nanometers, or 100 billionths of a meter. Defining whether a powder is non-nano or not is actually rather difficult as it is virtually impossible to ensure that a product is 100% nanoparticle free. Furthermore, many particles are not spherical in shape and thus are difficult to measure. The FDA has declined to weigh in on this controversial issue and does not currently define 'nano' or 'non nano' at this time. In the EU, non nano is defined as, "the primary particle size is greater than 100nm" (this is a somewhat vague definition). Australia defines non nano as "more than 90% of particles are above 100nm".
Badger has chosen to define non nano as "the primary particle size is greater than 100nm with no more than 10% falling within the upper nanoparticle range". Badger's definition for non nano is in line with the most stringent international definitions.
How does Badger substantiate our non-nano claim?
We used four methods of testing in order to verify our non-nano claim (see below). Additionally, we have a written statement from the zinc oxide manufacturer outlining how the process used to create our zinc oxide differs from that needed to make nanoparticle zinc oxide. Our zinc oxide manufacturer produces three cosmetic grades of zinc oxide; USP1 (the pharmaceutical non nano grade that Badger uses), a micronized (slightly smaller) grade, and a nanoparticle grade. They use the USP1 grade as the starting feed material for the other two grades, which are created through additional processing.
1. Scanning Electron Micrographs (see images below)
We took scanning electron microscope (SEM) images of our zinc oxide, and of three other types of zinc oxide commonly used in other sunscreens. We found the images facinating and thought you might like to see what zinc oxide particles look like under such powerful magnification. The manufacturer of Badger's zinc oxide claims it is: 'solid particle non-nano zinc oxide' and visual analysis of the SEM results show <10% free particles are below 100nm (and all particles appear greater than 70nm.) The manufacturer's claims of the other zinc oxides are printed above the images, they are 'non-nano clear zinc oxide', 'micronized zinc oxide', and 'nanoparticle zinc oxide'. All 4 of the SEM images are presented at the same scale (see 500nm scale bar on each) for comparison.
Scanning Electron Microscope Images of Four Sunscreen Zinc Oxides
2. Sedimentation Analysis
The particle size of our zinc oxide was also determined in a lab using a Sedigraph, or a device that measures particle settling rate and calculates particle size using Stokes Law. These results showed a median particle size of 293nm.
3. Surface Area Calculations
The manufacturer of our zinc oxide also used surface area calculations to estimate the particle size of our zinc oxide. They found that the mean surface particle diameter was 120nm. This number is not fully accurate as it is based on the assumption of a solid sphere, whereas the actual particles are irregular in shape. Many sunscreen manufacturers will use this single number to validate their non-nano claim, however, we feel that particle size should be measured in a distribution graph with a minimum, maximum, and mean for the greatest accuracy. See Light Scattering Analysis (below).
4. Light Scattering Analysis (see image below)
Light Scatter Analysis to determine our zinc oxide particle size was conducted by a third party independent lab. The results do not differentiate between agglomerated particles and free particles, however, they do accurately determine whether there are nano particles in the sample.
What is the zinc oxide nanoparticle controversy about anyway?
The nanoparticle controversy stems from the potential health risks caused by nanoparticles if they were to enter the human body. When a substance is so small that it is measured in nanometers (1 to 100 billionths of a meter), the surface area to volume ratio is so great that the actual properties of the substance may change. One comprehensive review of the scientific literature(1) shows that nano-particles of zinc oxide greater than 30nm do not exhibit properties any different than those of larger non-nano sized particles. Science overwhelmingly shows that particles of zinc oxide greater than 30nm, when applied to the skin in a lotion or cream based product, do not get absorbed into the body, do not enter the bloodstream, and are not a threat to human health.(1)(2)(3)(4)(5) There are no studies showing that nanoparticles of zinc oxide can penetrate healthy human skin, whereas chemical sunscreen ingredients, which are molecular in size and thus significantly smaller than nanoparticles, are designed to be absorbed into the skin, and thereby they can get into the blood. The biggest concern with nanoparticles in cosmetics is the threat of inhalation when they are used in powders and sprays. This is not a concern when the zinc oxide is dispersed in a cream or lotion base. Even the Environmental Working Group recommends the use of nano-sized mineral sunscreens over chemical sunscreens.
Why does Badger use non-nano zinc oxide?
Prior to 2011 we used ‘micronized’ zinc oxide (see photo above) which had a particle size ranging from 70nm to 300nm, in which about 20% of the particles were smaller than 100nm. We felt this zinc oxide offered excellent UVA and UVB protection, was relatively non-whitening, and was totally safe (all scientific literature concluded that particles in this size range do not penetrate the skin and are completely safe to use in sunscreen creams and lotions).We switched over to totally non-nano zinc oxide for two reasons. First, many of our customers asked us to stop using nanoparticles in our sunscreens. Second, we discovered a new way of working with larger particle zinc oxide that makes our sunscreens just as effective while using less zinc oxide. Our sunscreens are now even less whitening than when we used the smaller particles.
What does uncoated zinc oxide mean?
Many sunscreens use zinc oxide particles that have been coated with an inert substance. The reasons for coating zinc oxide particles are usually to make them less reactive (see below), and to make them easier to mix with the other ingredients. Badger used coated zinc oxide for years, until we found a better way to mix uncoated zinc oxide into our base then we switched to using larger particles (which are less reactive than smaller particles). The zinc oxide we now use in all our sunscreens is uncoated pharmaceutical grade zinc oxide, the same kind used in calamine lotion and diaper rash cream. We know that uncoated zinc oxide is somewhat more photo-reactive than coated zinc oxide, but we believe that this is not a health risk. Read details in the next section.
Are there any health risks with zinc oxide?
Zinc oxide, like most powders, can be a health risk if inhaled. This is not a concern with zinc oxide in cream and lotion-based sunscreens. Zinc oxide can also be photo-reactive, meaning that UV exposure can generate reactive oxygen species, or free radicals, which can damage living cells. This too is not a concern with the zinc oxide in our sunscreens because:
- The rate of reactivity is still very low compared to that of titanium dioxide, nanoparticle zinc oxide, and many other chemical sunscreen actives.(6)
- Zinc oxide sits on the outer, dead, layer of skin, and any free radicals generated will not affect living cells below.(4)
- Our inactive ingredients such as Organic Olive Oil, Sunflower Oil, Vitamin E, and more provide powerful antioxidants which help scavenge, or absorb, free radicals.
How does zinc oxide work as a sunscreen?
Zinc oxide is one of only 17 active ingredients currently approved by the FDA for use in sunscreens. Upon application, zinc oxide particles sit on the outermost layer of your skin, the stratum corneum, where they scatter and absorb ultraviolet radiation, protecting your living skin below. Zinc oxide is unique among sunscreen ingredients in that it is truly a broad-spectrum blocker, protecting from UVA, UVB, and even UVC. Titanium dioxide is another mineral active ingredient you may see in other brands' sunscreens. While it protects from UVB rays very well it does not protect from UVA as well as zinc oxide does.
Why does Badger use zinc oxide as the only active ingredient?
We've determined that zinc oxide is the safest, most effective active sunscreen ingredient available. It also stands alone in that it is a truly effective, single-ingredient, broad spectrum blocker, meaning that it protects from UVA, UVB, and even UVC rays. It also has a time tested safety record having been used in other topical drugs such as calamine lotion and diaper cream for a long time.
Why doesn't every sunscreen just use minerals such as zinc oxide and titanium dioxide instead of chemicals?
You have to use a lot of zinc oxide and/or titanium dioxide to get an SPF 30. This makes these mineral sunscreens expensive and whitening, so not everyone likes it. Have you noticed how much less expensive chemical based sunscreens are compared to mineral sunscreens? We feel that peace of mind is worth the additional cost and a little whitening on the skin.
What does Badger think about titanium dioxide?
We think that titanium dioxide is safe and effective for protection against UVB (and some UVA) rays, however, titanium dioxide should always be used in combination with zinc oxide to attain true broad spectrum protection. Truthfully, we think titanium dioxide received an unfair reputation when a 2011 Swiss study(7) likened titanium dioxide to asbestos. The study was referring to toxicity when inhaled, which is not a threat with sunscreen creams. The media did not seem to understand this and wrote several alarmist stories about the dangers of sunscreens containing titanium dioxide.
What does Badger think about chemical sunscreens?
We don't like them. We are concerned about the potential toxic effects of the chemicals when they enter the body. Oxybenzone, for example, is in about 60% of sunscreens sold in the US. The US Center for Disease Control found that 97% of Americans have oxybenzone in their blood(8). This ingredient has been shown to disrupt normal hormone functions and some health professionals are recommending that products containing this ingredient not be used on babies and kids. We are particularly concerned with the 'continuous spray' chemical sunscreens that are becoming so popular, mainly because of the risk of inhalation.
Here at Badger we, and most natural health advocates, including Dr. Andrew Weil(9), believe that zinc oxide sunscreens are better for your body than either chemical based sunscreens or exposing your skin to the sun without sunscreen. We follow all of the latest sunscreen research closely, and we remain convinced that our sunscreens at Badger are the most effective and the safest for human health and for the environment (see our page about Sunscreens and Coral Reefs). The best protection from the sun is to stay in the shade or wear protective clothing and a hat. But if you're going expose your skin to the sun you should protect it, and a zinc oxide sunscreen is the safest and most effective means to that end.
(1) Towards a Definition of
Inorganic Nanoparticles from an Environmental, Health and Safety Perspective. Auffan et. al. Nature Nanotechnology Sept. 13, 2009.
(2) Environmental Working Group's Sunscreen Guide
(3) Germany's Federal Institute for Risk Assessment (English website)
(4) Australian Government, Review of Scientific Literature
(5) FDAs Nanotechnology Scientific Research Website
(6) Smijs T. & Pavel, S. Titanium Dioxide and Zinc Oxide Nanoparticles in Sunscreens: Focus on Their Safety and Effectiveness; Nanotechnology, Science and Applications 2011:4 95–112.
(7) Amir S., Yazdi, et al. Nanoparticles activate the NLR pyrin domain containing 3 (Nlrp3) inflammasome and cause pulmonary inflammation through release of IL-1 and IL-1β PNAS 2010 107: 19449-19454.
(8) Calafat AM, Wong L-Y, Ye X, Reidy JA, Needham LL 2008. Concentrations of the Sunscreen Agent Benzophenone-3 in Residents of the United States: National Health and Nutrition Examination Survey 2003–2004. Environ Health Perspect 116:893-897
(9) Dr. Andrew Weil M.D.'s Question and Answer Library
Links to some helpful websites about sun protection.
•The Environmental Working Group's Sunscreen
•Sunscreen: The Burning Facts – Document by the Environmental Protection Agency
•American Academy of Dermatology's Facts About Sunscreens