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EWG 2014 Sunscreens Database
 
 

EWG’s methodology for assessing sunscreens

EWG’s 2014 Sunscreen Guide was researched and written by David Andrews, Ph.D., senior scientist; Samara Geller,database analyst; Sean Gray, M.S., senior analyst; Nneka Leiba, M.P.H., deputy director of research; Sonya Lunder, M.P.H., senior analyst; Paul Pestano, M.S., research analyst; and Renee Sharp, M.S., director of research.

Summary

EWG’s 8th annual analysis of sunscreens comprises safety and effectiveness ratings for more than 700sunscreens and SPF-labeled moisturizers. The ratings are based on an in-house compilation of standard industry, government and academic data sources, models we constructed over the past nine years and a thorough review of the technical literature on sunscreens. The sunscreen ratings from this investigation have been incorporated into EWG’s Skin Deep cosmetic safety database, an online consumer tool available at www.ewg.com/skindeep.
We based the analysis on sunscreen ingredient listings obtained primarily from online retailers. Products are rated on five factors encompassing overall ingredient safety and product efficacy in providing sun protection:

  • Health hazards associated with listed ingredients based on a review of nearly 60 standard industry, academic, government regulatory and toxicity databases
  • UVB protection (using SPF rating as the indicator of effectiveness);
  • UVA protection (using a standard industry absorbance model);
  • Balance of UVA/UVB protection (using the ratio of UVA absorbance to SPF);
  • Sunscreen stability (how quickly an ingredient breaks down in the sun, using an in-house stability database compiled from published findings of industry and peer-reviewed stability studies).

The overall rating for each product was calculated on the basis of a formula reflecting a combination of the product’s health hazard and efficacy ratings. Efficacy accounts for two-thirds of the score for products with lower health hazard concerns and for one-half the score in products with a high health hazard score.

The methods and content of the analysis were based on EWG’s review of the technical literature, including hundreds of industry and peer-reviewed studies. Results of the analysis appear in EWG’s online, interactive sunscreen guide. Details of the methodology are described below.

Safety Assessment (Health Hazard Score)

Health hazard scores were based on the ingredient health hazard scoring system of EWG’s Skin Deep database (www.ewg.org/skindeep). This core database of chemical hazards, regulatory status and study availability pools data from nearly 60 databases and from government agencies, industry panels, academic institutions or other credible bodies. The information in Skin Deep is used to create hazard ratings and data gap ratings for both personal care products and individual ingredients.

Additionally, the hazard score for mineral ingredients was adjusted to account for exposure potential calculated from evidence regarding skin penetration or absorption, as described in greater detail on the Skin Deep “About” page.

We gave additional weight in the calculated hazard scores to properties of particular concern for sunscreens, including products that contain oxybenzone or vitamin A, products in a spray or powder form that may pose a risk when inhaled, and products listing SPF values exceeding “SPF 50+, the limit suggested by the FDA in its 2011 proposed regulation (FDA 2011a,b). For sunscreens with a single significant concern, we assigned a rating no lower than 3 (moderate hazard), and for sunscreens with two or more significant concerns, we assigned a rating no lower than 7 to reflect a higher level of concern.

Health hazard scores in the sunscreen evaluations reflect hazards specific to sunscreens as well as beneficial or potentially harmful effects of specific combinations of active ingredients. We assessed hazards identified by government, industry, and academic sources but did not evaluate specific claims made by individual manufacturers.

This report includes a closer look at the 17 chemicals permitted by FDA for use as active ingredients in sunscreens (including the various particle sizes of the inorganic sunscreen ingredients zinc oxide and titanium dioxide), as well as the 52 chemicals used in other countries to prevent UV exposure that are added to U.S. sunscreens for other purposes. We compiled relevant information from sources that included published reports in the peer-reviewed literature and risk assessments from the European Union, Japan and Australia, countries with robust sunscreen regulations.

Assessing Known or Suspected Chemical Hazards

Sunscreens sold in the U.S. are considered over-the-counter (OTC) drugs. They contain active ingredients that must undergo safety and effectiveness testing and inactive ingredients that, as with virtually all other personal care products, are not required to be tested for safety. We used different approaches to evaluate active and inactive ingredients.
Active ingredients, as well as specific active ingredient combinations, were evaluated based on an extensive review of the scientific literature. The review included peer-reviewed literature, filed and approved patents and reviews by government and industry panels, as well as cross-checks with EWG’s Skin Deep database.

Inactive ingredient assessments were conducted using the existing Skin Deep system cited above (EWG 2014). Skin Deep identifies chemicals that pose health hazards, including known and probable carcinogens, reproductive and developmental toxicants, neurotoxic and immunotoxic chemicals, chemicals flagged for persistence, bioaccumulation and toxicity in the environment, as well as chemicals banned or restricted in other countries. Skin Deep assessments also highlight the extensive data gaps for the majority of ingredients used in cosmetics and personal care products.

Briefly, EWG’s hazard ratings are a synthesis of known and suspected hazards associated with ingredients and products. Skin Deep’s hazard ratings are categorized as raising low, moderate or higher concern, with numeric rankings that range from 0 (low concern) to 10 (higher concern). Data gap ratings describe the extent to which ingredients or products have been definitively assessed for safety. Data gap ratings are represented in Skin Deep by a numeric percentage ranging from 100% (complete absence of safety data) to 0% (comprehensive safety data).

Further details concerning this methodology may be found on the Skin Deep website (www.ewg.org/skindeep).

Sunscreen Efficacy (Sun Hazard)

Overview of Sunscreen Efficacy Evaluation

In the analysis of product effectiveness, we weighed four contributing factors:

  1. UVB protection
  2. UVA protection
  3. UVA/UVB balance
  4. Stability of active ingredient combinations, considering both the potential for active ingredient molecules to break down in sunlight, react with other ingredients or otherwise transform into compounds less effective at filtering UV radiation.

We assigned a score for each factor based on an evaluation of the labeled SPF, EWG-modeled UV protection and the technical literature on sunscreen stability.

We derived an overall rating for product effectiveness (sun hazard) as the sum of these four factors, weighted by their relative importance. In this calculation we assigned a weight of 0.28 each to UVA protection, UVB protection and UVA/UVB balanced protection, and a weight of 0.16 to stability. The procedures are described in greater detail below.

1. Evaluating Effectiveness of UVB Protection

UVB protection is based on each product’s SPF (Sun Protection Factor) rating as labeled on the product.

We scored UVB protection from sunscreens with SPF values between 15 and 110 as zero, or effective, for sunburn protection. This is based on the assumption that consumers would pick a product with the appropriate SPF based on their skin tone, solar intensity and time outdoors. Sunscreens with SPF values less than 15 are not evaluated in our database.

Modeling sunscreen efficacy to evaluate Products’ UVA protection

To score products on UVA protection (section 2) and the balance of UVA to UVB protection (section 3), we modeled the effectiveness of the sunscreen based on the active ingredients. Modeling the efficacy of sunscreen products based on the active ingredients is standard industry practice (BASF 2013). Modeling requires the absorbance spectrum for the active ingredient and the percent active ingredient used in the product.

Absorbance Spectra for Active Ingredients

Absorbance spectra are determined through experiments in which researchers measure the amount and type of UV light filtered out by an ingredient or ingredient combination at every wavelength along the UVA and UVB spectrum. With absorbance spectra, researchers determine the theoretical effectiveness of sunscreen ingredients and sunscreen products in preventing UV radiation from reaching the skin.

Figure 1: Example of modeled absorption spectrum of avobenzone

Ingredient Source
4-Methylbenzylidine Camphor (4-MBC) (Vanquerp 1999)
Avobenzone (Parsol 1789 | Butyl Methoxydibenzoylmethane) ( (Bonda 2005, BASF 2010)
Ensulizole (Phenylbenzimidazole Sulfonic Acid) (Inbaraj 2002)
Homosalate (Sánchez and Cuesta 2005)
Menthyl Anthranilate (Beeby and Jones 2000) (Beeby 2000)
Mexoryl SX (Herzog 2005b)
Sunscreen grade Titanium Dioxide (Schlossman 2005)1
Sunscreen grade Zinc Oxide (Schlossman 2005, EWG 2010, BASF 2009, Nanox 2009)1
Octinoxate (Octyl Methoxycinnamate) (Bonda 2005)
Octisalate (Octyl Salicylate) (Krishnan 2004)
Octocrylene (Sánchez 2005)
Oxybenzone (Benzophenone-3) (Vanquerp 1999)
Padimate O (Octyl Dimethyl PABA | PABA Ester) (Krishnan 2004)
Sulisobenzone (Benzophenone-4) (CIR 2006) (Sánchez 2005)
Tinosorb M (MBBT) (Herzog 2005b)
Tinosorb S (Herzog, Hueglin 2005b)

1 For inorganic active ingredients – titanium dioxide and zinc oxide – the “absorbance spectra” also takes into account the chemical’s ability to scatter UV radiation in the UVA range (Schlossman and Shao 2005). Two different zinc oxide spectra are used to reflect the large variation in efficacy with changing particle size. The default categorization for zinc oxide ingredients is particle size >100 nm (Lewicka 2011).

Absorbance spectra are represented in most of these sources either in graphic or tabular format as a function of wavelength. To use these absorbance spectra in our computations of sunscreen effectiveness, we developed an equation to represent each measured spectrum. When necessary, we digitized the graphical absorbance spectra from the sources listed above. We used the graphing and statistical analysis software package xmGrace (Turner, Team 2004) to determine the best-fit polynomial expression for each absorbance spectrum. The maximum error between the digitized data and final fitted values was 1%, and for any given point was less than 0.05% in most cases.

Monochromatic Protection Factor (MPF) and Transmission Spectra for Ingredients and Products

Both SPF and MPF are unitless factors that provide a measure of the amount of UV radiation blocked by sunscreen. SPF is a single value, while MPF varies based on wavelength. In the U.S., SPF is derived from sunburn experiments on human volunteers, while MPF is derived from lab measurements of UV transmission (Herzog 2005). SPF can also be computed by combining the MPF spectrum with the effective action spectrum (EA) for sunburn, a measure of how much damage a particular wavelength of light will cause (McKinlay 1987).

The MPF is a measure of the amount of UV radiation blocked (i.e., absorbed or scattered) at a particular wavelength and is a key component in EWG’s evaluation of sunscreen effectiveness. We developed UV transmission spectra for individual active ingredients and for all combinations of active ingredients in the products assessed. Our report uses the MPF transmission spectrum to graphically represent the effectiveness of sunscreen products and ingredients across the UV spectrum and to calculate the effectiveness of products in the UVA range. In the UVB range, we use SPF instead of MPF as the measure of product effectiveness.)

We computed the MPF transmission spectra following the method detailed by Herzog and implemented by the BASF sunscreen simulator (formerly the Ciba sunscreen simulator) (Herzog 2002, Herzog 2006, BASF 2011). This model accounts for the effect of uneven skin surfaces (skin is a series of ridges and valleys instead of a smooth surface). The model represents sunscreen on the skin as an unevenly distributed thin film. The sunscreen thickness is modeled using a continuous height distribution that matches a gamma distribution function (Ferrero 2003). The gamma method provides a significant improvement in the calculated correlation with measured SPF over the previously used two-step model (O’Neill 1984).

MPF is given by:

where T is the percent transmission of light, ε(λ) is the average molecular absorption coefficient (defined in Herzog), c is the average molar concentration of the active ingredients in moles/liter, d is the path length (20 micrometers is the assumed thickness of sunscreen based upon the recommended applied dose of 2 mg/cm2), and g and f are parameters fitted by Herzog (Herzog 2002, Herzog 2006) to match experimental data on European sunscreens equaling 0.269 and 0.935, respectively. Once the transmission spectrum is obtained, it can be transformed into an absorbance spectrum and monochromatic protection factors (MPF).

We used the Herzog method (Herzog 2002, Herzog 2006) described above to compute the UV transmission spectra both for individual ingredients and for all variations of active ingredients in the products assessed. The method requires inputting the concentrations of active ingredients. In computations of MPF spectra for individual ingredients, we used the average concentration of that ingredient found in the products assessed. In computations of MPF spectra, we used the concentrations of active ingredients specified on the product label. For some products, the concentrations of active ingredients were not available. In those cases, we used the following hierarchy to establish assumed concentrations of active ingredients used in the MPF analysis:

  1. Average concentration of active ingredient for products with the same SPF and active ingredient combination.
  2. Average concentration of active ingredient for products with the same SPF and active ingredient in a different combination.
  3. Average concentration of active ingredient for products with the same ingredient combination over all available SPFs.
  4. Average concentration of active ingredient for all products containing that active ingredient.

We evaluated sunscreen effectiveness based in part on our computation of the transmission spectrum for a product’s combination of active ingredients. We integrated over the combined effective absorbance spectrum as described by Herzog (Herzog 2002, Herzog 2006) over 1 nm wavelength intervals to obtain overall sunscreen product spectra based on the individual ingredient spectra described above. The spectral information is presented in this report over 10 nm wavelength intervals.

A sunscreen product must generally contain multiple active ingredients to achieve a high SPF rating due to FDA-imposed concentration limits and constraints on product formulation (Chatelain 2001).

2. Calculating the UVA Protection Score

In evaluating overall UVA effectiveness, the percentage of UVA light blocked or absorbed was calculated from our modeled spectrum of the product. This calculation provides a numeric measure of the degree of UVA protection. This value was calculated by integrating the MPF between 320-400nm.

Using this method, a score was assigned to each product:

Table 1: UVA score and percent of UVA light blocked

Percent UVA blocked or absorbed UVA Protection Score
>=93.6% 0
>=92.0% 1
>=90.0% 2
>=87.5% 3
>=84.4% 4
>=80.0% 5
>=75.0% 6
>=68.8% 7
>=60.0% 8
<60.0% 9

3. Calculating UVA/UVB Protection Balance

Government agencies, sunscreen researchers and the American Association of Dermatology recognize the need for sunscreens to offer proportionate protection from UVA and UVB radiation.

In 2009 we shifted from the spectral uniformity index for measuring sunscreen balance) to a method based on the ratio of our modeled UVA-PF to the labeled SPF. This method better accounts for imbalance, particularly in the high-SPF range, and relies directly on manufacturers’ measured SPF values rather than modeled values.

We calculated a balance factor for each sunscreen as the ratio of the UVA Protection Factor (UVA-PF) for persistent pigment darkening to the SPF value listed on product labels.

Using this method, a UVA/UVB balance score was assigned to each product:

Table 2: UVA/UVB balance score scoring

Ratio of UVA-PF/SPF UVA/UVB Balance Score
>90% 0
>66% 1
>33% 2
>29% 3
>25% 4
>21% 5
>16% 6
>14% 7
>11% 8
<11% 9

Calculating the Number of Sunscreens that Meet the European COLIPA UVA Standard

The European standard for UVA protection in sunscreens set by Cosmetics Europe – The Personal Care Association requires sunscreens to have both a critical wavelength of 370 nm and a ratio of UVA protection factor/SPF greater than 1/3. The UVA protection factor is calculated by weighting the absorbance spectrum between 320 to 400 nm with the persistent pigment-darkening action spectra (Cosmetics Europe 2011).

The New FDA Standard for Broad Spectrum Protection

Starting in mid-December 2012, sunscreens sold and labeled as providing broad-spectrum protection are required to have a critical wavelength of 370 nm (FDA 2011). The new FDA standards do little to differentiate mediocre from excellent products. The standards have been criticized for providing no incentive for improvement (Diffey 2012).

4. Ingredient Stability

Absorption of UV light causes many sunscreen active ingredients to undergo chemical reactions or structural changes on the skin. In most cases, these ingredients quickly return to their original form to absorb more energy. However, ingredients can also degrade and may lose their UV protectiveness. A study by Shaath found that seven of 14 common sunscreens in Europe photo-degraded significantly after exposure to UV radiation, specifically UVA (Shaath, Fares 1990).

In certain cases, degradation may produce other chemicals that are toxic to skin and body cells, especially if the sunscreen has been absorbed into the skin (Gasparro 1997), or the reactions can speed up (catalyze) degradation of other ingredients in the sunscreen mixture (Bonda 2005).

Ideally, EWG would like to have laboratory results of photo-degradation for every active ingredient in every sunscreen product. However, since this information is not publicly available and such testing is not required of manufacturers, we analyzed a large number of studies from various sources. In quantifying these studies, it is difficult to compare results of different studies because of differences in the experimental conditions (solvent versus sunscreen formulation, measurement of light energy, sample preparation). Additionally, the degradation rate of an ingredient in a dilute laboratory solvent such as water or ethanol may or may not be representative of the results during consumer use. Even results in one sunscreen formulation may not be representative of the results in another because of variations in how active ingredients behave in different environments.

EWG performed linear regression analysis of percent degradation versus minimal erythemal dose (MED) exposures in solvent and sunscreen formulations. The regression equations for solvent and sunscreen systems were then weighted equally and classified into three categories:

Table 3: Scoring ingredient stability

Stability Classification Extent of Photo-degradation after 2 hours of peak intensity sun exposure (10 MEDs)
Major Photo-degradation over 25% breakdown
Minor Photo-degradation 5% to 25% breakdown
No Photo-degradation (Photo-stable) less than 5% breakdown

We weighted solvent and formulation results equally because of the wide variation in test conditions and the possibility that a single sunscreen formulation may not be representative of other formulations.

There is insufficient information in the literature on the subject of photo-stability to reliably guide a sunscreen formulator, let alone the consumer. Our classifications are presented here:

Table 4: Degradation of active ingredients

Active Ingredient Classification Percent Degradation with exposure to 10 MEDs
4-Methylbenzylidine Camphor (4-MBC) (Deflandre 1988; Vanquerp 1999) None Less than 1
Avobenzone (Parsol 1789 | Butyl Methoxydibenzoylmethane) (Deflandre 1988; Shaath 1990; Roscher 1994; Schwack 1995) Major 42.1
Ensulizole (Phenylbenzimidazole Sulfonic Acid) (Deflandre 1988, Serpone 2002) — Deflandre found insignificant degradation in a sunscreen formulation, Serpone measured fast degradation in various solvents. Major 46.6
Homosalate (Berset 1996, Herzog 2002) Minor 6.7 – 60
Menthyl Anthranilate (Beeby 2000) None No degradation
Mexoryl SX (TDSA) (Deflandre 1988, Cantrell 1999, Herzog, Hueglin 2005) Minor 21.2
Micronized Titanium Dioxide (Schlossman and Shao 2005) None No degradation
Micronized Zinc Oxide (Schlossman and Shao 2005) None No degradation
Octinoxate (Octyl Methoxycinnamate) (Deflandre 1988, Shaath 1990, Berset 1996, Chatelain 2001, Serpone 2002) Minor 24.8
Octisalate (Octyl Salicylate) (Shaath 1990, Bonda 2005) None 3.3
Octocrylene (Shaath 1990, Bonda 2005) None 1.6
Oxybenzone (Benzophenone-3) (Deflandre 1988, Shaath 1990, Roscher 1994, Berset 1996, Chatelain 2001, Serpone 2002) Minor 21.9
Padimate O (Octyl Dimethyl PABA | PABA Ester) (Deflandre 1988, Serpone 2002) Major 44.7
Sulisobenzone (Benzophenone-4) (CIR 2006) None No degradation expected
Tinosorb M (MBBT) (Herzo, 2002, Herzog 2005) None 1
Tinosorb S (BEMT) (Chatelain 2001, Bonda 2005, Damiani 2007) None 1

In order to account for a situation where an individual ingredient may photo-degrade but the sunscreen itself continues to provide significant protection due to the presence of other active ingredients, we assumed that the UV blocking effectiveness of an active ingredient experiencing major degradation is reduced by 50%, and the UV-blocking effectiveness of an active ingredient with minor degradation is reduced by 25%.

We then re-integrated over the entire spectrum and compared the degraded spectrum to the original. UVA and UVB protection were weighted equally. Based on the relative amount of degradation, the following scores were applied separately to the UVA and UVB portions:

Table 5: Stability scoring

% blocking remaining after 10 MED (approximately 2 hours of sun exposure) Score
% Area >90% 0
80 < % Area< 90% 1
70% < % Area< 80% 2
60% < % Area< 70% 3
% Area <60% 4

Menthyl Anthranilate and Padimate O fluoresce when exposed to sunlight, meaning they absorb energy in the UVB range and re-emit it in the UVA range. If an active ingredient fluoresces, we increased the stability score by 1 point.

The scores for UVA, UVB and fluorescence were added together to determine the overall stability score, which ranges from 0 to 9, and were then scaled to a range of 0 to 10.

Several inactive ingredients help prevent sun damage through mechanisms other than blocking UV rays. For example, a variety of antioxidants scavenge free radicals in cells (Klein 2005). In some cases, claims made for these ingredients are unregulated (Klein 2005), while in others, the SPF itself can no longer be predicted by the sun blocking ability of the actives alone (Stanfield 2005). In the later case, consumers are misled into believing they are receiving more protection than they actually are. For these ingredients, we attenuate the UVA and UVB scores as follows:

Table 6: Antioxidant scoring adjustments

Raw Score Score Category Description
Attenuating score (improves UVB score by 10%) Additional protection against UVB induced damage anti-oxidants protect against UVB induced radiation damage
Attenuating score (improves UVA score by 10%) Additional protection against UVA induced damage anti-oxidants protect against UVA induced radiation damage

Particle Size Assumptions for Mineral Sunscreens

The absorbance spectra for titanium dioxide and zinc oxide vary based on the size of the particle. Companies are not required to provide particle size information on package labels, leaving EWG with little information to determine the size and properties of the specific mineral ingredients used (FOE 2009, FDA 2007). EWG based the absorbance spectra on an average of the most likely particle sizes found products containing titanium dioxide and zinc oxide. The information was based on our review of particle size and surface coatings for zinc oxide and titanium dioxide found on the company websites of sunscreen manufacturers and formulators.

Titanium Dioxide

When the shortest dimension of the primary particles of titanium dioxide is 15 nm, it appears transparent on skin, but at 35-60 nm it becomes opaque (Schlossman 2005). All information we have amassed about 10 different titanium dioxide suppliers indicated primary particle sizes of 10-35 nm. Without clear regulatory guidelines, manufacturers and product formulators can claim they are using or not using nanoparticles without providing information to back up that claim. We assume that all UV attenuation-grade titanium dioxide sunscreens that appear clear on the skin use titanium dioxide with a mean primary particle size of 15-35 nm in the shortest dimension.

Table 7: Characteristics of sunscreen-grade titanium dioxide

Titanium Dioxide Suppliers and Products
Supplier Product Crystal form Primary particle size Surface coating Source
BASF T-Lite SF-S Rutile 30 nm*60 nm*10 nm, may aggregate into larger particles Methicone Gamer 2006
BASF T-LITE SF Rutile 30 nm*60 nm*10 nm, may aggregate into larger particles Silica, Methicone Gamer 2006
BASF Uvinul TiO2 75% anatase/25% rutile 21 nm, agglomerate to 100 nm trimethoxyoctysilyl BASF 2006
Degussa P-25 Anatase 21 nm None, trimethyloctylsilane Mavon 2007
EMD, Rona/Merck Eusolex T-2000 Anatase 10 to 20 * 100 nm (possibly due to agglomeration) Alumina, Dimethicone NanoDerm 2007, SCCNFP 2000
EMD, Rona/Merck Eusolex T-45D Anatase 10-15 nm Alumina/simethicone, oil dispersion Sayre 2000
EMD, Rona/Merck Eusolex T-AQUA Anatase 10-15 nm Alumina, water dispersion Sayre 2000
ISK TTO S-4 Rutile 15 nm AHSA Schlossman 2005
ISK TTO S-3 Rutile 15 nm Alumina Schlossman 2005
ISK TTO V-3 Rutile 10 nm Alumina Schlossman 2005
Kemira UV Titan M170 Rutile 14 nm Alumina, Methicone Schlossman 2005
Kemira UV Titan M262 Rutile 20 nm Alumina, Dimethicone SCCNFP 2000
Kobo Products TEL-100 At least one dimension >100 nm, particles >100 when dispersed in ester Aluminum hydroxide and silica Kobo 2009
Kobo Products MPT-154-NJE8 At least one dimension >100 nm Alumina and jojoba esters Kobo 2009
Kobo Products TTO-NJE8 At least one dimension >100 nm Alumina and jojoba esters Kobo 2009
Sachtleben Hombitec L5 Anatase est. 15 nm (80-160 m2/g) Silica, Silicone Schlossman 2005
Showa Denka Maxlight TS-04 35 nm Silica Schlossman 2005
Tayca MT-100T Rutile 15 nm AS/AH SCCNFP 2000
Tayca MT-500B Rutile 35 nm Alumina Schlossman 2005
Tayca MT-100Z Rutile 15 nm AS/AH Schlossman 2005
Titan Kogyo Stt 65C-S Anatase est. 20 nm (64 m2/g) None Schlossman 2005

Zinc Oxide

Scientists estimate zinc oxide provides maximum UVB protection with particles sized 20 to 30 nm, and the typical sizes of zinc particles in sunscreen are 30 to 200 nm (BASF 2011, Cross 2007, Nohynek 2007, Stamatakis 1990). Compared to larger particles, smaller particles provide greater UVB protection but less UVA protection (Schlossman 2005). Particles larger than about 200-300 nm tint the skin white and are unacceptable to most consumers (BASF 2000).

By default, EWG has assumed that zinc oxide used as an active ingredient in sunscreens has a 140 nm mean primary particle size. This applies when manufacturers indicate they use Z-Cote or non-nano minerals.

Table 8: Characteristics of sunscreen-grade zinc oxide

Zinc Oxide Suppliers and Products
Supplier Product Primary particle size Surface coating Source
Antria/Dow Zinclear-IM 50AB 2740nm C12-15 Alkyl Benzoate (and) Isostearic Acid (and) Polyhydroxystearic Acid Antaria 2010, Dow 2011
Antria/Dow Zinclear-IM 50CCT 2740nm Caprylic/Capric Triglyceride (and) Glyceryl Isostearate (and) Polyhydroxystearic Acid Antaria 2010, Dow 2011
Antria/Dow Zinclear-IM 50JJ 2740nm Simmondsia Chinensis (Jojoba) Seed Oil (and) Glyceryl Isostearate (and) Polyhydroxystearic Acid Antaria 2010, Dow 2011
Antria/Dow Zinclear-IM 55L7 2740nm Neopentyl Glycol Diheptanoate (and) Glyceryl Isostearate (and) Polyhydroxystearic Acid (and) Cetyl PEG-PPG-10/1 Dimethicone Antaria 2010, Dow 2011
BASF Z-Cote 80 nm (30 to 200 nm) uncoated or dimethicone BASF 2010
Elementis Nanox 200 60 nm (17 m2/g) None Schlossman 2005
Kobo Products ZnO-C-12 At least one dimension >100 nm Isopropyl Titanium Triisostearate Kobo 2009
Kobo Products ZnO-C-11S4 At least one dimension >100 nm Triethoxycaprylysilane Kobo 2009
Kobo Products ZnO-C-NJE3 At least one dimension >100 nm Jojoba esters Kobo 2009
Kobo Products ZnO-C-DMC2 At least one dimension >100 nm Diemethicone/Methicone Copolymer Kobo 2009
Sakai Finex, SF-20 60 nm (20 m2/g) None Schlossman 2005
Showa Denka ZS-032 31 nm Silica Schlossman 2005
Sumitomo Cement ZnO-350 35 nm None Schlossman 2005
Tayca MZ-700 10-20 nm None Schlossman 2005
Tayca MZ-500 20-30 nm None Schlossman 2005
Tayca MZ-300 30-40 nm None Schlossman 2005

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