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Evaluating products' effectiveness for UVA protection

Government agencies and sunscreen manufacturers have not agreed on a single, standardized test to capture the UVA protection of a sunscreen. EWG selected 2 in vitro methods, the 'Critical Wavelength Approach' and the 'Boots Star Rating System,' to determine the UVA protection of sunscreens. The benefit of the Critical Wavelength Approach is that it captures the effects of exposure over the full UVA spectrum. In contrast, the Boots Star Rating System captures the intensity of UVA protection at a wavelength in the UVA range. The 2 methods are weighted equally in the overall UVA score.

Critical Wavelength Method

The Critical Wavelength Approach is outlined by Diffey (Diffey 1994; Diffey, Tanner et al. 2000) and supported by the American Academy of Dermatologists (AAD 2002). Diffey's approach determines UVA protectiveness in the region between 290 and 400 nm. The Critical Wavelength is the point on the spectrum between 290 and 400 nm where 90% of the total absorbance occurs. A sunscreen is considered broad-spectrum if the critical wavelength is above 370 nm (Diffey 1994) or 360 nm (CTFA/NDMA 1996).

We computed the Critical Wavelength for each active ingredient and each product in our analysis by integrating over the relevant UV absorption spectrum to find the wavelength corresponding to 90% of the area under the curve between 290 and 400 nm:

We assigned interim scaling factors between 1 and 2 to each of the computed Critical Wavelength for ingredient and products evaluated as follows:

Critical Wavelength (nm)	Value
> = 370 nm	1
365 to 370 nm	1.25
360 to 365 nm	1.5
< 360 nm	2

Average light blocked

The critical wavelength metric weighs the shape of the absorption curve more heavily than the magnitude. Both are important, and we offset this limitation in our evaluation of a product's UVA effectiveness by incorporating a second UVA metric, the average UVA light blocked. It is useful because it better captures the intensity of UVA protection.

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

Average UVA absorption	>=80%	70-80%	60-70%	50-60%	40-50%	<40%
Score	1	2	3	4	5	6

Calculating the overall UVA protection score

By combining results from the 2 methods described above we can account for the two critical factors in UVA protection: broad coverage across the whole UVA spectrum, and the magnitude of protection.

The 2 methods were combined by multiplying the Critical Wavelength value (1 to 2) by the average UVA absorption score (1 to 6) for every product evaluated. This gives a range of 1 to 12. We normalize the resulting values to the standard 0 to 10 scale we use across our sunscreen evaluation and our Skin Deep personal care product assessment methodology.

Standard methods are needed to assess UVA protection.

These methods were selected as an interim method for informing present day consumer choices. More robust in vivo methods should be developed for measuring UVA protection. The American Academy of Dermatologists recommends an in vivo method, such as persistent pigment darkening, or immediate pigment darkening (AAD 2002). However, the development and standardization of new methods is the responsibility of FDA and cosmetic companies, and should include a comparable metric that is relevant to human health. The cosmetics industry first raised this issue in 1996 (CTFA/NDMA 1996), and eleven years later, consumers still have no basis to know if a product adequately products from UVA rays.

Evaluating products' effectiveness for UVB protection

We based our evaluation of UVB protection on each product's SPF (Sun Protection Factor), which is the accepted metric for evaluating UVB protectiveness. We scaled the SPF factor to create a UVB rating for each product that ranged from 0 (effective) to 10 (ineffective). This calculation involved the following:

We set a linear relationship between SPF and a product's UVB rating using two pre-established points on the line, defining a UVB rating of 1 (effective) to SPF 30 products, and a UVB rating of 6.4 to SPF 15 products (moderately effective). These points were set to correspond to the 3 standard score ranges we have established in our personal care product rating systems used in this sunscreen analysis as well as in our Skin Deep personal care product assessment guide.

Our standard 3-tiered scoring system maps integer scores from 0 to 10 into the following 3 categories: 0-2 (low hazard or effective); 3-6 (moderate concern or moderate effectiveness); and 7-10 (higher concern or ineffective). A value of 6.4 was selected for SPF 15 products to correspond to the top of the mid-range (moderate) score range, before truncation to an integer value. This effectively sets SPF 15 at the end of the "moderate" score range, and SPF values less than 15 in the "ineffective" score range to reflect the fact that sunscreens with SPF<15 are generally not recommended by health authorities for sun protection (e.g., AAD 2006).

With this linear relationship established between the UVB rating and SPF, we then calculated scores for the full range of SPF values on products using the following procedure:

• We calculated UVB ratings for products with SPF values from 5 to 30 and by interpolating or extrapolating along the line described above.
• We set the UVB rating at 10 (ineffective) for products with SPF values of 5 or less.
• We set the UVB rating at zero (effective) for products with SPF values of "30+" or with listed SPF values exceeding 30.

SPF	% UVB spectrum blocked	UVB hazard score	Color on spectrum
30	97	1	Darkest
15	93	6	Lighter
8	88	9	Lighter
4	75	10	Lighter
0 to 4	50	10	White — little protection

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. In fact, a study by Shaath found that 7 out of 14 common sunscreens in Europe photodegraded significantly after exposure to UV radiation, specifically UVA radiation (Shaath, Fares et al. 1990).

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

Ideally, we'd know laboratory results of photodegradation for each active ingredient in every sunscreen product. Since this information is not publicly available and such testing is not required of manufacturers, a large number of studies from different sources needed to be analyzed. In quantifying these studies, it is difficult to compare results between different studies because different experimental conditions were used (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 the way different actives behave in different environments.

EWG performed linear regression analysis of percent degradation versus minimal erythmal dose (MED) exposures on solvent and sunscreen formulations. The regression equations for solvent and sunscreen systems were then weighted equally and classified into 3 categories:

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

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

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

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

In order to account for a situation where an individual ingredient may photodegrade, but the sunscreen itself continues to provide significant protection relative to its original level due to the presence of other active ingredients, we assume 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-integrate over the entire spectrum and compare the degraded spectrum to the original. UVA and UVB protection are weighted equally. Based on the amount of relative degradation, the following scores are applied separately to the UVA and UVB portions:

% 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 in energy in the UVB range, and re-emit it in the UVA range. If an active ingredient fluoresces, then we assign it an additional 1point to the stability score.

The scores for UVA, UVB and fluorescence were added together for the overall stability score, which ranges from 0 to 9, and was 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 anti-oxidants scavenge free radicals in cells (Klein and Palefsky 2005). In some cases, claims made with these ingredients are unregulated (Klein and Palefsky 2005), while in others, the SPF itself can no longer be predicted by the sunblocking 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:

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

Safety Assessment (Hazard Score)

EWG's health hazard scores were based upon the ingredient health hazard scoring system from our Skin Deep database (www.cosmeticsdatabase.com). This core database of chemical hazards, regulatory status, and study availability pools the data of nearly 60 databases and sources 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 personal care products, as well as for individual ingredients.

With this report, the Skin Deep scoring system has been extended to include additional hazards specific to sunscreens, as well as beneficial or potentially harmful effects of specific combinations of active ingredients. As in Skin Deep, we looked only at hazards identified by government, industry, and academic sources, and 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 sunscreen (including the various sizes of inorganic sunscreens), and the 52 chemicals used in other countries to prevent UV exposure and added to U.S. sunscreens for another purpose. This 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) drug products. They contain active ingredients that must undergo safety and effectiveness testing, and inactive ingredients that, like virtually all other personal care product ingredients, are not required to be tested for safety before they are sold. We used different approaches to evaluate active and inactive ingredients.

Active ingredient assessments, as well as assessments of specific active ingredient combinations, were evaluated by conducting 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 the existing Skin Deep databases. Certain inactive ingredients, such as those that are approved as active ingredients outside the U.S., are also treated as active ingredients for the health and sun hazard reviews.

Inactive ingredient assessments were conducted using the existing Skin Deep system mentioned above (EWG 2007). Skin Deep identifies chemicals with health hazards including known and probable carcinogens, reproductive and developmental toxicants, neurotoxic and immunotoxic chemicals, chemicals flagged for their persistence, bioaccumulation, and toxicity, and 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, hazard ratings are a synthesis of known and suspected hazards associated with ingredients and products. Hazard ratings within Skin Deep are shown as low, moderate, or higher concern categories, with numeric rankings spanning those categories 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 their safety. Data gap ratings are represented within Skin Deep by a numeric percentage ranging from 0% (complete absence of safety data) to 100% (comprehensive safety data).

Further details concerning this methodology may be found on the Skin Deep website (www.cosmeticsdatabase.com).

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