Protector solar , también conocida como crema solar , protector solar o bronceadores , es una loción , aerosol, gel, espuma (tal como una loción expandido espuma o loción batida), palo u otro tópica producto que absorbe o refleja algo de la sol 's ultravioleta ( UV) y, por lo tanto, ayuda a proteger contra las quemaduras solares . El uso diligente de protector solar también puede ayudar a retrasar o prevenir temporalmente el desarrollo de arrugas, manchas oscuras y piel flácida.
Protector solar | |
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Otros nombres | Bloqueador solar, bloqueador solar, crema solar, crema solar, bloqueador [1] |
Dependiendo del modo de acción, los protectores solares se pueden clasificar en protectores solares físicos (es decir, óxido de zinc y dióxido de titanio, que permanecen en la superficie de la piel y desvían principalmente [ cita requerida ] [2] la luz ultravioleta) o protectores solares químicos (es decir, , Filtros orgánicos UV, que absorben la luz UV).
Organizaciones médicas como la Sociedad Estadounidense del Cáncer recomiendan el uso de protector solar porque ayuda en la prevención de los carcinomas de células escamosas . [3] El uso rutinario de protectores solares también puede reducir el riesgo de melanoma . [4] Sin embargo, muchos protectores solares no bloquean la radiación UVA (UVA), sin embargo, la protección contra los UVA es importante para la prevención del cáncer de piel. [5]
Para proporcionar una mejor indicación de su capacidad para proteger contra el cáncer de piel y otras enfermedades asociadas con la radiación UVA (como la fitofotodermatitis [6] ), se ha recomendado el uso de protectores solares de amplio espectro ( UVA / UVB ). [7]
En los Estados Unidos, se requiere que los protectores solares sigan siendo efectivos en su concentración original durante al menos tres años. Algunos protectores solares incluyen una fecha de vencimiento, una fecha que indica cuándo pueden volverse menos efectivos. [8]
Efectos en la salud
Beneficios
El uso de protector solar puede ayudar a prevenir el melanoma [9] [10] [11] y el carcinoma de células escamosas , dos tipos de cáncer de piel . [12] Hay poca evidencia de que sea eficaz para prevenir el carcinoma de células basales . [13]
Un estudio de 2013 concluyó que la aplicación diaria y diligente de protector solar podría retrasar o prevenir temporalmente el desarrollo de arrugas y flacidez de la piel. [14] El estudio involucró a 900 personas blancas en Australia y requirió que algunas de ellas se aplicaran un protector solar de amplio espectro todos los días durante cuatro años y medio. Encontró que las personas que lo hicieron tenían una piel notablemente más resistente y suave que las asignadas para continuar con sus prácticas habituales. [14] Un estudio en 32 sujetos mostró que el uso diario de protector solar (SPF 30) revirtió el fotoenvejecimiento de la piel en 12 semanas y la mejora continuó hasta el final del período de investigación de un año. [15]
Minimizar el daño de los rayos UV es especialmente importante para los niños y las personas de piel clara y para aquellos que tienen sensibilidad al sol por razones médicas. [dieciséis]
Riesgos potenciales
En 2009, la Administración de Productos Terapéuticos de Australia actualizó una revisión de los estudios de seguridad de los protectores solares y concluyó: "El potencial de las nanopartículas de dióxido de titanio (TiO 2 ) y óxido de zinc (ZnO) en los protectores solares para causar efectos adversos depende principalmente de la capacidad de las nanopartículas para alcanzar células cutáneas viables. Hasta la fecha, el peso actual de la evidencia sugiere que las nanopartículas de TiO 2 y ZnO no alcanzan las células cutáneas viables ". [17] Los ingredientes de los protectores solares generalmente se someten a una revisión exhaustiva por parte de los reguladores gubernamentales en varios países, y los ingredientes que presentan problemas importantes de seguridad (como PABA ) tienden a retirarse del mercado de consumo. [18]
Existe el riesgo de una reacción alérgica al protector solar para algunas personas, ya que "La dermatitis alérgica de contacto típica puede ocurrir en personas alérgicas a cualquiera de los ingredientes que se encuentran en los productos de protección solar o en las preparaciones cosméticas que tienen un componente de protección solar. La erupción puede ocurrir en cualquier lugar en el cuerpo donde se ha aplicado la sustancia y, a veces, puede extenderse a lugares inesperados ". [19]
Producción de vitamina D
También se han planteado preocupaciones [ ¿coloquialismo? ] sobre la posible deficiencia de vitamina D derivada del uso prolongado de protector solar. [ cuando? ] El uso típico de protector solar no suele provocar una deficiencia de vitamina D; sin embargo, el uso extensivo puede. [20] El protector solar evita que la luz ultravioleta llegue a la piel, e incluso una protección moderada puede reducir sustancialmente la síntesis de vitamina D. [21] [22] Sin embargo, se pueden producir cantidades adecuadas de vitamina D con una exposición moderada al sol en la cara, los brazos y las piernas, con un promedio de 5 a 30 minutos dos veces por semana sin protector solar. (Cuanto más oscura es la tez, o más débil es la luz solar, se necesitan más minutos de exposición, aproximadamente el 25% del tiempo para una mínima quemadura solar). La sobredosis de vitamina D es imposible debido a la exposición a los rayos UV debido al equilibrio que alcanza la piel en el que la vitamina D se degrada tan rápido como se crea. [23] [24] [25]
Estos estudios anteriores [ ¿cuáles? ] se confirmaron en 2019, que mostraron que el protector solar con un factor de protección UVA alto permitía una síntesis de vitamina D significativamente más alta que un protector solar con factor de protección UVA bajo, probablemente porque permite una mayor transmisión de UVB. [26] [27]
Medidas de protección
Factor de protección solar y etiquetado
El factor de protección solar (clasificación SPF, introducido en 1974) es una medida de la fracción de rayos ultravioleta que producen quemaduras solares y llegan a la piel. Por ejemplo, "SPF 15" significa que 1 ⁄ 15 de la radiación ardiente llegará a la piel, suponiendo que el protector solar se aplique uniformemente en una dosis espesa de 2 miligramos por centímetro cuadrado [28] (mg / cm 2 ). Un usuario puede determinar la efectividad de un protector solar multiplicando el FPS por el tiempo que le toma sufrir una quemadura sin protector solar. [29] Por lo tanto, si una persona desarrolla una quemadura solar en 10 minutos cuando no usa protector solar, la misma persona con la misma intensidad de luz solar tardará 150 minutos en desarrollar una quemadura solar de la misma gravedad si usa protector solar con un FPS de 15. . [29] es importante señalar que los protectores solares con FPS más alto no duran o siguen siendo eficaces en la piel por más tiempo que el menor SPF y deben volver a aplicar continuamente como se indica, por lo general cada dos horas. [30]
El SPF es una medida imperfecta del daño cutáneo porque el daño invisible y el envejecimiento cutáneo también son causados por el ultravioleta tipo A (UVA, longitudes de onda 315–400 o 320–400 nm ), que no causa principalmente enrojecimiento o dolor. El protector solar convencional bloquea muy poca radiación UVA en relación con el SPF nominal; Los protectores solares de amplio espectro están diseñados para proteger contra los rayos UVB y UVA. [31] [32] [33] Según un estudio de 2004, los rayos UVA también causan daño en el ADN de las células profundas de la piel, lo que aumenta el riesgo de melanomas malignos . [34] Incluso algunos productos etiquetados como "protección UVA / UVB de amplio espectro" no siempre han proporcionado una buena protección contra los rayos UVA. [35] El dióxido de titanio probablemente brinda una buena protección, pero no cubre completamente el espectro UVA, ya que la investigación de principios de la década de 2000 sugiere que el óxido de zinc es superior al dióxido de titanio en longitudes de onda de 340 a 380 nm. [36]
Debido a la confusión de los consumidores sobre el grado real y la duración de la protección ofrecida, en varios países se aplican restricciones de etiquetado. En la UE , las etiquetas de los protectores solares solo pueden llegar hasta SPF 50+ (inicialmente enumeradas como 30 pero pronto revisadas a 50). [37] Australia 's Administración de Productos Terapéuticos aumentó el límite superior de 50+ en 2012. [38] [39] En su proyecto de normas 2007 y 2011, los EE.UU. Administración de Alimentos y Medicamentos (FDA) propuso una etiqueta SPF máximo de 50, para limitar afirmaciones poco realistas. [40] [7] [41] (A febrero de 2017, la FDA no ha adoptado el límite de SPF 50. [42] ) Otros han propuesto restringir los ingredientes activos a un SPF de no más de 50, debido a la falta de pruebas. que las dosis más altas brindan una protección más significativa. [43] Los diferentes ingredientes de los filtros solares tienen una eficacia diferente contra los rayos UVA y UVB. [44]
El SPF se puede medir aplicando protector solar a la piel de un voluntario y midiendo cuánto tiempo pasa antes de que se produzca una quemadura solar cuando se expone a una fuente de luz solar artificial. En los EE. UU., La FDA exige una prueba in vivo de este tipo. También se puede medir in vitro con la ayuda de un espectrómetro especialmente diseñado . En este caso, se mide la transmitancia real del protector solar, junto con la degradación del producto debido a la exposición a la luz solar. En este caso, la transmitancia del protector solar debe medirse en todas las longitudes de onda en el rango UVB-UVA de la luz solar (290-400 nm), junto con una tabla de qué tan efectivas son las distintas longitudes de onda para causar quemaduras solares (el espectro de acción eritemal ) y el estándar. espectro de intensidad de la luz solar (ver figura). Tales mediciones in vitro concuerdan muy bien con las mediciones in vivo . [ atribución necesaria ]
Se han ideado numerosos métodos para evaluar la protección UVA y UVB. Los métodos espectrofotoquímicos más fiables eliminan la naturaleza subjetiva del eritema de clasificación . [45]
El factor de protección ultravioleta (UPF) es una escala similar desarrollada para calificar telas para ropa de protección solar . Según pruebas recientes de Consumer Reports , UPF ~ 30 + es típico para telas protectoras, mientras que UPF ~ 20 es típico para telas estándar de verano. [46]
Matemáticamente, el SPF (o el UPF) se calcula a partir de datos medidos como: [ cita requerida ]
dónde es el espectro de irradiancia solar, el espectro de acción eritemal, y el factor de protección monocromático, todas las funciones de la longitud de onda . El MPF es aproximadamente el inverso de la transmitancia a una longitud de onda determinada. [ cita requerida ]
Lo anterior significa que el SPF no es simplemente el inverso de la transmitancia en la región UVB. Si eso fuera cierto, entonces aplicar dos capas de protector solar SPF 5 siempre sería equivalente a SPF 25 (5 veces 5). El SPF combinado real puede ser menor que el cuadrado del SPF de una sola capa. [47]
Protección UVA
Oscurecimiento persistente del pigmento
El método de oscurecimiento persistente del pigmento (PPD) es un método para medir la protección UVA, similar al método SPF para medir la protección contra quemaduras solares. Desarrollado originalmente en Japón, es el método preferido de fabricantes como L'Oréal .
Instead of measuring erythema, the PPD method uses UVA radiation to cause a persistent darkening or tanning of the skin. Theoretically, a sunscreen with a PPD rating of 10 should allow a person 10 times as much UVA exposure as would be without protection. The PPD method is an in vivo test like SPF. In addition, Colipa has introduced a method that, it is claimed, can measure this in vitro and provide parity with the PPD method.[48]
SPF equivalence
As part of revised guidelines for sunscreens in the EU, there is a requirement to provide the consumer with a minimum level of UVA protection in relation to the SPF. This should be a "UVA PF" of at least 1/3 of the SPF to carry the UVA seal.[49]
A set of final US FDA rules effective from summer 2012 defines the phrase "broad spectrum" as providing UVA protection proportional to the UVB protection, using a standardized testing method.[7]
Star rating system
In the UK and Ireland, the Boots star rating system is a proprietary in vitro method used to describe the ratio of UVA to UVB protection offered by sunscreen creams and sprays. Based on original work by Brian Diffey at Newcastle University, the Boots Company in Nottingham, UK, developed a method that has been widely adopted by companies marketing these products in the UK.
One-star products provide the lowest ratio of UVA protection, five-star products the highest. The method was recently revised in light of the Colipa UVA PF test and the revised EU recommendations regarding UVA PF. The method still uses a spectrophotometer to measure absorption of UVA versus UVB; the difference stems from a requirement to pre-irradiate samples (where this was not previously required) to give a better indication of UVA protection and photostability when the product is used. With the current methodology, the lowest rating is three stars, the highest being five stars.
In August 2007, the FDA put out for consultation the proposal that a version of this protocol be used to inform users of American product of the protection that it gives against UVA;[40] but this was not adopted, for fear it would be too confusing.[43]
PA system
Asian brands, particularly Japanese ones, tend to use The Protection Grade of UVA (PA) system to measure the UVA protection that a sunscreen provides. The PA system is based on the PPD reaction and is now widely adopted on the labels of sunscreens. According to the Japan Cosmetic Industry Association, PA+ corresponds to a UVA protection factor between two and four, PA++ between four and eight, and PA+++ more than eight. This system was revised in 2013 to include PA++++ which corresponds to a PPD rating of sixteen or above.
Sunblock
Sunblock typically refers to opaque sunscreen that is effective at blocking both UVA and UVB rays and uses a heavy carrier oil to resist being washed off. Titanium dioxide and zinc oxide are two minerals that are used in sunblock.[50]
The use of the word "sunblock" in the marketing of sunscreens is controversial. Since 2013, the FDA has banned such use because it can lead consumers to overestimate the effectiveness of products so labeled.[7] Nonetheless, many consumers use the words sunblock and sunscreen synonymously.
For total protection against damage from the sun, the skin needs to be protected from UVA, UVB, and also IRA (infrared-A light).[51] Infrared radiation accounts for roughly 40% of solar energy at sea level.[52] There is continuing debate within the dermatology community over the impact of sun-sourced IRA: Some sources indicate that early morning IRA exposure may be protective against further sun exposure by increasing cell proliferation and initiating anti-inflammatory cascades; these effects are not observed for artificial sources of intense IRA.[52]
Ingredientes activos
In addition to moisturizers and other inactive ingredients, sunscreens contain one or more of the following active ingredients, which are either organic or mineral in nature:
- Organic chemical compounds that absorb ultraviolet light.
- Inorganic particulates that reflect, scatter, and absorb UV light (such as titanium dioxide, zinc oxide, or a combination of both).[50]
- Organic particulates that mostly absorb UV light like organic chemical compounds, but contain multiple chromophores that reflect and scatter a fraction of light like inorganic particulates. An example is Tinosorb M. The mode of action is about 90% by absorption and 10% by scattering.
The principal active ingredients in sunscreens are usually aromatic molecules conjugated with carbonyl groups. This general structure allows the molecule to absorb high-energy ultraviolet rays and release the energy as lower-energy rays, thereby preventing the skin-damaging ultraviolet rays from reaching the skin. So, upon exposure to UV light, most of the ingredients (with the notable exception of avobenzone) do not undergo significant chemical change, allowing these ingredients to retain the UV-absorbing potency without significant photodegradation.[53] A chemical stabilizer is included in some sunscreens containing avobenzone to slow its breakdown; examples include formulations containing. The stability of avobenzone can also be improved by bemotrizinol,[54] octocrylene[55] and various other photostabilisers. Most organic compounds in sunscreens slowly degrade and become less effective over the course of several years even if stored properly, resulting in the expiration dates calculated for the product.[56]
Sunscreening agents are used in some hair care products such as shampoos, conditioners and styling agents to protect against protein degradation and color loss. Currently, benzophenone-4 and ethylhexyl methoxycinnamate are the two sunscreens most commonly used in hair products. The common sunscreens used on skin are rarely used for hair products due to their texture and weight effects.
The following are the FDA allowable active ingredients in sunscreens:
UV-filter | Other names | Maximum concentration | Permitted in these countries | Results of safety testing | UVA | UVB |
---|---|---|---|---|---|---|
p-Aminobenzoic acid | PABA | 15% (EU: banned from sale to consumers from 8 October 2009) | USA, AUS | Protects against skin tumors in mice.[57][58][59] Shown to increase DNA defects, however, and is now less commonly used. | X | |
Padimate O | OD-PABA, octyldimethyl-PABA, σ-PABA | 8% (EU, USA, AUS) 10% (JP) (Not currently supported in EU and may be delisted) | EU, USA, AUS, JP | X | ||
Phenylbenzimidazole sulfonic acid | Ensulizole, Eusolex 232, PBSA, Parsol HS | 4% (US, AUS) 8% (EU) 3% (JP) | EU, USA, AUS, JP | Genotoxic in bacteria[60] | X | |
Cinoxate | 2-Ethoxyethyl p-methoxycinnamate | 3% (US) 6% (AUS) | USA, AUS | X | X | |
Dioxybenzone | Benzophenone-8 | 3% | USA, AUS | X | X | |
Oxybenzone | Benzophenone-3, Eusolex 4360, Escalol 567 | 6% (US) 10% (AUS, EU) 5% (JP) | EU, USA, AUS, JP | X | X | |
Homosalate | Homomethyl salicylate, HMS | 10% (EU, JP) 15% (US, AUS) | EU, USA, AUS, JP | X | ||
Menthyl anthranilate | Meradimate | 5% | USA, AUS | X | ||
Octocrylene | Eusolex OCR, Parsol 340, 2-Cyano-3,3-diphenyl acrylic acid, 2-ethylhexylester | 10% | EU, USA, AUS, JP | Increases reactive oxygen species (ROS)[61] | X | X |
Octyl methoxycinnamate | Octinoxate, EMC, OMC, Ethylhexyl methoxycinnamate, Escalol 557, 2-Ethylhexyl-paramethoxycinnamate, Parsol MCX | 7.5% (US) 10% (EU, AUS) 20% (JP) | EU, USA, AUS, JP | Banned in Hawaii starting in 2021 - harmful to coral[62] | X | |
Octyl salicylate | Octisalate, 2-Ethylhexyl salicylate, Escalol 587, | 5% (EU, USA, AUS) 10% (JP) | EU, USA, AUS, JP | X | ||
Sulisobenzone | 2-Hydroxy-4-Methoxybenzophenone-5-sulfonic acid, 3-Benzoyl-4-hydroxy-6-methoxybenzenesulfonic acid, Benzophenone-4, Escalol 577 | 5% (EU) 10% (US, AUS, JP) | EU, USA, AUS, JP | X | X | |
Trolamine salicylate | Triethanolamine salicylate | 12% | USA, AUS | X | ||
Avobenzone | 1-(4-methoxyphenyl)-3-(4-tert-butyl phenyl)propane-1,3-dione, Butyl methoxy dibenzoylmethane, BMDBM, Parsol 1789, Eusolex 9020 | 3% (US) 5% (EU, AUS) 10% (JP) | EU, USA, AUS, JP | X | ||
Ecamsule | Mexoryl SX, Terephthalylidene Dicamphor Sulfonic Acid | 10% | EU, AUS (US: approved in certain formulations up to 3% via New Drug Application (NDA) Route) | Protects against skin tumors in mice[63][64][65] | X | |
Titanium dioxide | CI77891 | 25% (US) No limit (JP) | EU, USA, AUS, JP | X | ||
Zinc oxide | 25% (US) No limit (AUS, JP) | EU, USA, AUS, JP | Protects against skin tumors in mice[63] | X | X |
Zinc oxide was approved as a UV filter by the EU in 2016.[66]
Other ingredients approved within the EU[67] and other parts of the world,[68] that have not been included in the current FDA Monograph:
UV-filter | Other names | Maximum concentration | Permitted in |
---|---|---|---|
4-Methylbenzylidene camphor | Enzacamene, Parsol 5000, Eusolex 6300, MBC | 4%* | EU, AUS |
Parsol Max, Tinosorb M | Bisoctrizole, Methylene Bis-Benzotriazolyl Tetramethylbutylphenol, MBBT | 10%* | EU, AUS, JP |
Parsol Shield, Tinosorb S | Bis-ethylhexyloxyphenol methoxyphenol triazine, Bemotrizinol, BEMT, anisotriazine | 10% (EU, AUS) 3% (JP)* | EU, AUS, JP |
Tinosorb A2B | Tris-Biphenyl Triazine | 10% | EU |
Neo Heliopan AP | Bisdisulizole Disodium, Disodium phenyl dibenzimidazole tetrasulfonate, bisimidazylate, DPDT | 10% | EU, AUS |
Mexoryl XL | Drometrizole Trisiloxane | 15% | EU, AUS |
Benzophenone-9 | Uvinul DS 49, CAS 3121-60-6, Sodium Dihydroxy Dimethoxy Disulfobenzophenone [69] | 10% | JP |
Uvinul T 150 | Octyl triazone, ethylhexyl triazone, EHT | 5% (EU, AUS) 3% (JP)* | EU, AUS |
Uvinul A Plus | Diethylamino Hydroxybenzoyl Hexyl Benzoate | 10% (EU, JP) | EU, JP |
Uvasorb HEB | Iscotrizinol, Diethylhexyl butamido triazone, DBT | 10% (EU) 5% (JP)* | EU, JP |
Parsol SLX | Dimethico-diethylbenzalmalonate, Polysilicone-15 | 10% | EU, AUS, JP |
Amiloxate | Isopentyl-4-methoxycinnamate, Isoamyl p-Methoxycinnamate, IMC, Neo Heliopan E1000 | 10%* | EU, AUS |
* Time and Extent Application (TEA), Proposed Rule on FDA approval originally expected 2009, now expected 2015.
Many of the ingredients awaiting approval by the FDA were relatively new, and developed to absorb UVA.[70] The 2014 Sunscreen Innovation Act was passed to accelerate the FDA approval process.[71][72]
Solicitud
The dose used in FDA sunscreen testing is 2 mg/cm2 of exposed skin.[53] If one assumes an "average" adult build of height 5 ft 4 in (163 cm) and weight 150 lb (68 kg) with a 32-inch (82-cm) waist, that adult wearing a bathing suit covering the groin area should apply approximately 30 g (or 30 ml, approximately 1 oz) evenly to the uncovered body area. This can be more easily thought of as a "golf ball" size amount of product per body, or at least six teaspoonfuls. Larger or smaller individuals should scale these quantities accordingly.[73] Considering only the face, this translates to about 1/4 to 1/3 of a teaspoon for the average adult face.
Some studies have shown that people commonly apply only 1/4 to 1/2 of the amount recommended for achieving the rated sun protection factor (SPF), and in consequence the effective SPF should be downgraded to a 4th root or a square root of the advertised value, respectively.[47] A later study found a significant exponential relation between SPF and the amount of sunscreen applied, and the results are closer to linearity than expected by theory.[74]
Claims that substances in pill form can act as sunscreen are false and disallowed in the United States.[75]
Regulación
- Palau
On 1 January 2020, Palau becomes the first country in the world to ban sun cream that is harmful to corals and sea life. The ban comes into effect immediately after an announcement by President Tommy Remengesau Jr.[76]
- Hawaii
The island state of Hawaii is to ban the commercial sale of sunscreens containing oxybenzone and octinoxate on January 1, 2021 due to concern of environmental effects linked to the two ingredients and their contribution to increased coral bleaching [1]. This ban is only applicable to sale within the state and to sunscreen products, not other cosmetic materials.
- United States
Sunscreen labeling standards have been evolving in the United States since the FDA first adopted the SPF calculation in 1978.[77] The FDA issued a comprehensive set of rules in June 2011, taking effect in 2012–2013, designed to help consumers identify and select suitable sunscreen products offering protection from sunburn, early skin aging, and skin cancer:[7][78][79]
- To be classified as "broad spectrum", sunscreen products must provide protection against both UVA and UVB, with specific tests required for both.
- Claims of products being "waterproof" or "sweatproof" are prohibited, while "sunblock" and "instant protection" and "protection for more than 2 hours" are all prohibited without specific FDA approval.
- "Water resistance" claims on the front label must indicate how long the sunscreen remains effective and specify whether this applies to swimming or sweating, based on standard testing.
- Sunscreens must include standardized "Drug Facts" information on the container. However, there is no regulation that deems it necessary to mention whether the contents contain nanoparticles of mineral ingredients. (The EU has stricter regulation against the use of nanoparticles, and in 2009 introduced labeling requirements for nanoparticle ingredients in certain sunscreens and cosmetics.)[80]
In 2019, the FDA proposed tighter regulations on sun protection and general safety, including the requirement that sunblock products with SPF greater than 15 must be broad spectrum and a prohibition on products with SPF greater than 60.[81]
In the United States, sunscreen can be purchased using a tax-advantaged health savings account (HSA) or flexible spending account (FSA).[82][83]
Efectos ambientales
Certain sunscreens in water under ultraviolet light can increase the production of hydrogen peroxide, which damages phytoplankton.[84]
A 2002 study suggests that sunscreen causes an increase in virus abundance in seawater, leading to poor marine environment health similar to that of other pollutants.[85]
A 2008 study that tested different sunscreen brands, protective factors, and concentrations found that they all caused bleaching on hard corals, and the rate of beaching increased with increased quantity of sunscreen. Of the compounds found in sunscreen that were tested separately, "butylparaben, ethylhexylmethoxycinnamate, benzophenone-3 and 4-methylbenzylidene camphor caused complete bleaching even at very low concentrations."[86]
Media reports link oxybenzone in sunscreens to coral bleaching,[87] although some environmental experts dispute the claim.[88] A 2015 study published in the Archives of Environmental Contamination and Toxicology linked oxybenzone to effects on cell culture experiments and juvenile coral,[89] but other sources of pollution such as agricultural run-off and sewage probably have a larger impact on coral reefs.[90] The purported link between oxybenzone and coral decline is widely disputed within the environmental community.[87][additional citation(s) needed]
In 2018, the Pacific nation of Palau has become the first country to ban sun creams containing oxybenzone, octinoxate, and some other harmful elements.[91]
A 2019 study of UV filters in oceans found far lower concentrations of oxybenzone than previously reported, and lower than known thresholds for environmental toxicity.[92][93] Additionally, the National Oceanic and Atmospheric Administration (NOAA) has indicated that coral decline is associated with effects from climate change (warming oceans, rising water levels, acidification), overfishing, and pollution from agriculture, wastewater, and urban run-off.[94]
Historia
Early civilizations used a variety of plant products to help protect the skin from sun damage. For example, ancient Greeks used olive oil for this purpose, and ancient Egyptians used extracts of rice, jasmine, and lupine plants whose products are still used in skin care today.[95] Zinc oxide paste has also been popular for skin protection for thousands of years.[96] Among the nomadic sea-going Sama-Bajau people of the Philippines, Malaysia, and Indonesia, a common type of sun protection was a paste called borak or burak, which was made from water weeds, rice and spices. It was used most commonly by women to protect the face and exposed skin areas from the harsh tropical sun at sea.[97] In Myanmar, thanaka, a yellow-white cosmetic paste made of ground bark, is traditionally used for sun protection.
Early synthetic sunscreens were first used in 1928.[95] The first major commercial product was brought to market in 1936, introduced by the founder of L'Oreal, French chemist Eugène Schueller.[98]
Among widely used modern sunscreens, one of the earliest was produced in 1944 for the US military by Benjamin Green, an airman and later a pharmacist, as the hazards of sun overexposure became apparent to soldiers in the Pacific tropics at the height of World War II.[18][98][99][100] The product, named Red Vet Pet (for red veterinary petrolatum), had limited effectiveness, working as a physical blocker of ultraviolet radiation. It was a disagreeable red, sticky substance similar to petroleum jelly. Sales boomed when Coppertone improved and commercialized the substance under the Coppertone girl and Bain de Soleil branding in the early 1950s.
In 1946, Austrian chemist Franz Greiter introduced what may have been the first effective modern sunscreen. The product, called Gletscher Crème (Glacier Cream), subsequently became the basis for the company Piz Buin, which is still today a marketer of sunscreen products, named in honor of the mountain where Greiter allegedly received the sunburn that inspired his concoction.[101][102][103] In 1974, Greiter adapted earlier calculations from Friedrich Ellinger and Rudolf Schulze and introduced the "sun protection factor" (SPF), which has become a worldwide standard for measuring the effectiveness of sunscreen.[18][104] It has been estimated that Gletscher Crème had an SPF of 2.
Water-resistant sunscreens were introduced in 1977,[98] and recent development efforts have focused on overcoming later concerns by making sunscreen protection both longer-lasting and broader-spectrum, as well as more appealing to use.[18]
Investigar
New products are in development such as sunscreens based on bioadhesive nanoparticles. These function by encapsulating commercially used UV filters, while being not only adherent to the skin but also non-penetrant. This strategy inhibits primary UV-induced damage as well as secondary free radicals.[105]
Also UV filters based on sinapate esters are under study.[106]
Notas
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enlaces externos
- Does it work, or not? – illustrated explanation of how UV light is absorbed by chemicals in sunscreen from Wired
- 56% of Americans Rarely or Never Use Sunscreen - A survey conducted about the sunscreen habits of modern Americans.