Sunscreens Safety, Efficacy and Appropriate Use
Abstract
摘要
英文原文
Promoting sunscreen use is an integral part of prevention programmes aimed at reducing ultraviolet (UV) radiationinduced skin damage and skin cancers. Protection against both UVB and UV A radiation is advocated. Most sunscreens combine chemical UV absorbing sunscreens and physical inorganic sunscreens, which reflect UV, to provide broadspectrum protection. Newer triazole and camphorderivative based sunscreens, also provide broad-spectrum protection and are more cosmetically acceptable than many traditional agents. Currently licensed sunscreen ingredients in common use rarely cause allergic or photoallergic reactions. Vitamin D levels are not significantly affected by regular use of a sunscreen. Sunscreen use reduces both the development of precancerous solar keratosis and the recurrence of squamous cell carcinomas. Sunscreen use early in life may be important in prevention of basal cell carcinomas. Increased melanoma risk is influenced by the behaviour patterns of regular sunscreen users, as opposed to any direct effect of sunscreens. Sun protection factor (SPF) is affected by application density, water resistance and other factors. An adequate SPF for an individual should be balanced to skin phenotype and exposure habits. The correct use of sunscreens should be combined with the avoidance of midday sun and the wearing of protective clothing and glasses, as part of an overall sun protection regimen.
对应中文
推广使用防晒霜是旨在减少紫外线（UV）辐射引起的皮肤损伤和皮肤癌的预防方案的组成部分。大多数防晒霜结合化学紫外线吸收防晒霜和物理无机防晒霜（反射）【小绛解读：此处敬待后期分析】，以提供广谱防护。新型三唑类和樟脑衍生物防晒霜也提供广谱保护，在美容上比许多传统的防晒剂更容易接受。目前常用的防晒霜成分很少引起过敏或光敏反应。经常使用防晒霜对维生素D水平没有明显影响。使用防晒霜可以减少癌前日光角化症的发展和鳞状细胞癌的复发。生命早期使用防晒霜可能对预防基底细胞癌很重要。与防晒霜的任何直接作用相反，经常使用防晒霜的人的行为模式会影响黑色素瘤风险的增加。防晒系数(SPF)受应用密度、耐水性等因素的影响。对于个人来说，适当的SPF应该与皮肤表型和暴露习惯相平衡。正确使用防晒霜应与避免正午阳光、穿防护服和戴防护眼镜相结合，作为整体防晒方案的一部分。
英文原文
Skin cancer is the most common malignancy in the western world, where the continued vogue for sunbathing and the use of sunbeds has been paralleled by an increasing incidence of nonmelanoma and melanoma skin cancers. Such trends have prompted active campaigns by medical groups and health authorities to promote an increased awareness of the potential harmful effects of prolonged sunlight exposure. Exposure to sunlight induces chronic damage, including premature aging and skin cancers. Those with fair skin types are most at risk. In many countries primary prevention programmes are in place aimed at reducing sun exposure. High profile campaigns such as the ‘slip, slap, slop’ message (slip on a T-shirt, slap on a hat, slop on some sunscreen) introduced in Australia about 15 years ago have had a marked effect on raising public awareness. A recent survey in Australia indicated that nearly 75% of women and 60% of men apply sunscreen on a sunny day.The emphasis in these campaigns has centred on a positive message advocating how to behave appropriately in the sun. Motivating people towards employing immediate measures to prevent longterm problems has always proved a difficult prospect especially when tanned skin remains in vogue. Many people, therefore, continue to ignore the consequences of excess sun exposure despite intensive education campaigns.
对应中文
皮肤癌是西方世界最常见的恶性肿瘤，在西方，日光浴和日光浴的持续流行与非黑色素瘤和黑色素瘤皮肤癌发病率的上升同步。这种趋势促使医疗团体和卫生机构开展积极的运动，以提高人们对长期暴露在阳光下的潜在危害的认识。暴露在阳光下会导致慢性损伤，包括过早衰老和皮肤可再生障碍性疾病。那些皮肤白皙的人面临的风险最大。许多国家都制定了旨在减少阳光照射的预防计划。大约15年前在澳大利亚推出的“slip，slap，slop”（穿上T恤，戴上帽子，涂上防晒霜）等引人注目的宣传活动对提高公众意识产生了显著效果。澳大利亚最近的一项调查表明，近75%的女性和60%的男性在阳光明媚的日子涂抹防晒霜。这些活动的重点集中在一个积极的信息上，即提倡如何在阳光下采取正确的措施。鼓励人们立即采取措施预防远期问题一直是个难题，尤其是在皮肤美黑仍然比较流行的情况下。因此，尽管开展了密集的教育活动，许多人仍然忽视过度暴露在阳光下的后果。
英文原文
An integral part of the strategy to reduce photodamage has been the use of sunscreens. Sunscreens have been commercially available for seventy years, but the past 30 years has seen this area develop into a multibillion dollar industry. Manufacturers now incorporate sunscreens into a wide variety of cosmetics, make up and moisturisers. The sunscreen acts to prevent photodegradation of the product on the shelf, in conjunction with its protective role against the photodamaging effects of both UVB and UV A radiation. The bewildering array of new sunscreens that are available over the counter, are subject to regulation in both the US and Europe, which leads to improved efficacy, tolerability and acceptability of these products.
对应中文
减少光损伤的策略中不可或缺的一部分就是使用防晒霜。防晒霜在商业上已经有70年的历史了，但在过去的30年里，这个领域已经发展成为一个数十亿美元的产业。制造商现在把防晒霜加入到各种各样的化妆品、化妆品和保湿霜中。防晒霜的作用是防止以上产品的光降解，同时起到抵御紫外线和UVA辐射的光破坏效应的作用。在美国和欧洲，柜台上出售的一系列令人眼花缭乱的新型防晒霜都受到监管，从而提高了这些产品的功效、耐受性和可接受性。
英文原文
The ultraviolet (UV) component of electromagnetic radiation from the sun is divided into UVC (100 to 290nm) which does not reach the earth’ s surface, UVB (290 to 315nm) and UV A (315 to 400nm). The atmosphere typically absorbs 100% of UVC, 90% of UVB and negligible amounts of UVA radiation. UV radiation reaching the ground at midday is 90% UVA and 10% UVB. It is the significantly more biologically active UVB (from 600 to 1000 times more erythemogenic than UV A), which mainly causes sun- burn, with maximal redness and pain peaking 24 hours post ex- posure. UV intensity is determined primarily by solar angle, lat- itude, time of day, season, cloud cover and ozone levels. UVB intensity gradually decreases with increasing atmospheric transit from midday but UVA intensity is less influenced by time and is prevalent throughout the day.
对应中文
太阳电磁辐射的紫外线（UV）成分分为未到达地球表面的UVC（100-290nm）、到达地球表面的UVB（290-315nm）和UVA（315-400nm）。大气通常吸收100%的UVC、90%的UVB和可忽略的UVA辐射。中午到达地面的紫外线辐射为90%UVA和10%UVB。这部分UVB生物活性明显更高（比UVA的致红性高600到1000倍），主要引起晒伤，在晒伤后24小时出现最大程度的红肿和疼痛。紫外线强度主要由太阳角度、纬度、一天中的时间、季节、云量和臭氧水平决定。从正午开始，UVB强度随着大气传输的增加而逐渐降低，但UVA强度受时间的影响较小，并且在一天中普遍存在。
Classification of Sunscreens
防晒霜的分类
英文原文
Sunscreen ingredients are broadly classified on the basis of their mode of UV protection, acting as either chemical absorbers of certain wavelengths of UV light, or physical blockers that reflect most UV radiation. Chemical absorbers are further subclassified as absorbing UVB, UV A or both. Most sunscreens provide enhanced photoprotection to a wider spectrum of UV absorption, by means of a combination of individual UVB and UVA filters. The addition of antioxidants to sunscreens such as α-tocopherol, betacarotene and ascorbic acid (vitamin C), provide little extra photoprotection but may stabilize photoactive molecules.Their limitations as antioxidants in vivo are primarily because of poor diffusion into the epidermis.
对应中文
防晒成分根据其紫外线防护模式进行广泛分类，既可以作为特定波长紫外线的化学吸收剂，也可以作为反射大部分紫外线辐射的物理阻挡剂【小绛解读：此处容易产生误解，敬待后期分析】。化学吸收剂又细分为吸收UVB、UVA或两者兼而有之。大多数防晒霜通过单独的UVB和UVA滤光片的组合，为更宽的紫外线吸收光谱提供增强的光保护。在防晒霜中添加抗氧化剂，如α-生育酚、β-胡萝卜素和抗坏血酸（维生素C），几乎不提供额外的光保护，但可能稳定光活性分子。它们在体内作为抗氧化剂的局限性主要是因为它们很难扩散到表皮。
Chemical Ultraviolet Absorbers
化学紫外线吸收剂
英文原文
Despite the long list of available UV filters, most sunscreens worldwide rely on a core group of sunscreens in their formulation. A review of most commercially available sunscreens will reveal at least one, or a combination of the following. Cinnamates were one of the earliest developed sunscreens and octyl methoxycinna- mate remains one of the most commonly used and effective UVB absorbers.Newer cinnamates such as octocrylene are also found in many commercially available sunscreens, in combination with other sunscreens. It is used to improve the water resistance of many formulations and increases photostability of dibenzoylmethanes. Oxybenzone, which blocks both UVB and UV A, has been used in Europe since 1980, usually in combination with other UVB filters to improve SPF.
对应中文
尽管现有的紫外线过滤器很多，但世界上大多数防晒霜在配方中都依赖于一组核心防晒成分。回顾一下大多数市面上可以买到的防晒霜，就会发现至少有一种，或者是以下几种防晒成分的组合。肉桂酸酯是最早开发出来的防晒成分之一，而甲氧基辛酯仍然是最常用和最有效的紫外线吸收剂之一。较新的肉桂酸盐、如丙烯酸辛酯与其他防晒成分的组合在许多市售防晒霜中也很常见。它用于改善许多配方的耐水性，并提高二苯甲酰甲烷的光稳定性。自1980年以来，氧苯酮已在欧洲开始使用，通常与其他UVB滤光片结合使用，以提高SPF值。它可以阻挡UVB和UVA两种物质。
英文原文
Of the salicylates, octyl salicylate is more commonly used in the US than Europe. While salicylates are relatively weak UV absorbers, between wavelength 300 to 310nm, their excellent tolerability profile, stability and nonwater solubility, allow for improved substantivity and use as a combination product in many sunscreens. The paraAminobenzoic acid (PABA) derivatives have experienced a worldwide decline in popularity since the 1960s, to be replaced by PABA-free sunscreens. A combination of its ability to cause sensitization and crosssensitization with compounds of similar chemical structures, combined with staining of clothes and skin, have led to gradual market withdrawal. New photostable chemicals have been recently developed. Drometriazole, terephthalylidene dicamphor sulphonic acid, bisethylhexyloxyphenol methoxyphenol triazine, and methylene bisbenzotriazolyl tetramethylbutylphenol are new broad spectrum stable sunscreens, the main disadvantage of which lies in their relative expense compared with older products.
对应中文
在水杨酸盐中，水杨酸辛酯在美国比在欧洲更常用。虽然水杨酸盐是相对较弱的紫外吸收剂，在波长300-310nm之间，但其优异的透光性、稳定性和非水溶性，使其具有更好的实用性、并可作为多种防晒霜的组合产品使用。自20世纪60年代以来，对氨基苯甲酸(PABA)衍生物在世界范围内的受欢迎程度有所下降，取而代之的是不含PABA的防晒霜。由于其与化学结构相似的化合物具有敏化和交叉敏化的能力，再加上对衣服和皮肤的染色，导致了市场的逐步退出。近来开发出的新耐光化学品：去甲三唑、对苯二甲酰二氨基磺酸、双-乙基己基氧基苯酚甲氧基苯酚三嗪和亚甲基双-苯并三唑四甲基丁基苯酚是新的广谱稳定防晒剂，其主要缺点在于与旧产品相比其费用相对较高。
Physical Blockers
物理阻滞剂
英文原文
Physical or inorganic sunscreens reflect or scatter UV radiation. This ability is determined by a number of factors including the particle size, amount of sunscreen applied, the refractive index and its dispersion in a base. The particle size of traditional agents such as titanium dioxide and zinc oxide was in the region of 100 to 300 microns, thus preventing systemic absorption. Zinc oxide is shown to be insoluble with no change in serum zinc levels after application of zinc oxide to intact or psoriatic skin.These inorganic sunscreens were generally viewed as safer than their organic counterparts. Furthermore, the addition of iron oxide provides broader UV protection extending into the UV A and visible light range.These sunscreens were available as thick white or coloured pastes. Their tendency to comedogenesis and stain clothes made them undesirable to most consumers. Studies suggested that this cosmetic undesirability resulted in smaller amounts of sunscreen used, providing an SPF of roughly half that achieved with chemical sunscreens.
对应中文
物理或无机防晒霜反射或散射紫外线辐射【小绛解读：此处容易产生误解，敬待后期分析】。这种能力由许多因素决定，包括颗粒大小、涂抹的防晒霜量、折射指数及其在基底中的分散度。二氧化钛和氧化锌等传统药剂的粒径在100到300微米之间，因此阻碍了全身吸收。在正常或牛皮癣皮肤上涂抹氧化锌后，氧化锌被证明是不溶的，血清锌水平没有变化。无机防晒霜通常被认为比有机防晒霜更安全。此外，添加氧化铁可提供更广泛的紫外线防护，延伸至UVA和可见光范围。这些防晒霜可作为粉底或遮瑕膏提供。但它们引起粉刺特性和弄脏衣服的可能性使它们不受大多数消费者的欢迎。研究表明，这种不受欢迎的化妆品导致防晒霜的使用量较少，提供的SPF大约是化学防晒霜的一半。
英文原文
In the early 1990s, micronized forms of physical sunscreen became available, with particle size of 20 to 50 microns. This smaller particle size renders the particle invisible on the skin and shifts the protection offered towards the UVB end of the spectrum. Microfine titanium dioxide thus attenuates UVB and UVA II (315 to 340nm), however it is less effective than zinc oxide in the UVA I range (340 to 400nm).It is now formulated in the less photoactive rutile form and the particles are coated in aluminium oxide, zirconium or silicon, making it less reactive. Microfine zinc oxide is shown to be photostable and nonphotoreactive with other organic compounds when combined within a sunscreen. Physical sunscreens are compatible in combination with other physical sunscreens or with traditional organic UV filters. This acts to increase the SPF and provide broader UV spectrum protection.
对应中文
20世纪90年代初，出现了粒径为20至50微米的超细物理防晒霜。这种较小的颗粒尺寸使得颗粒在皮肤上不可见，并将提供的保护移向光谱的UVB端。因此，微细二氧化钛可以衰减UVB和UVA II(315到340 nm)，但在UVA I波段(340到400 nm)它的效果不如氧化锌。它现在的配方是光活性较低的金红石形式，颗粒被包裹在氧化铝、锆或硅中，使其反应性减弱。微细氧化锌被证明是光稳定性的，与其他有机化合物结合在防晒霜中时不会发生光反应。物理防晒霜可与其他物理防晒霜或传统或有机紫外线过滤器相结合。这可以提高SPF值，并提供更广泛的紫外光谱保护。
Tolerability
耐受性
英文原文
With the correct use and correct choice of sunscreen, many of the immediate tolerability considerations are avoided, however concern remains regarding potential long term tolerability issues with sunscreen use. It has been suggested that regular sunscreen use may predispose to vitamin D deficiency, with a subsequent effect on development of osteomalacia and cancer prevention.The active form of vitamin D, 1,25 dihydroxyvitamin D, has been postulated to prevent cancer on the basis of in vitro studies showing suppression of melanocyte proliferation. Reassuringly, regular use of sunscreen (SPF 15) has been shown not to decrease serum vitamin D concentrations sufficiently, either to induce changes in parathyroid function, or in metabolic bone markers.
对应中文
正确使用和正确选择防晒霜，可以避免许多直接的耐受性考虑，但对防晒霜使用的潜在长期耐受性问题仍然存在担忧。有人认为，经常使用防晒霜可能导致维生素D缺乏，继而对骨软化的发生和癌症的预防产生影响。维生素D的活性形式1，25-二羟基维生素D是根据体外研究显示抑制黑素细胞增殖而被推定为预防癌症的。令人放心的是，正常使用防晒霜(SPF15)并不能充分降低血清维生素D浓度，这既不会引起甲状旁腺功能的改变，也不会引起代谢骨标志物的改变。
英文原文
Sunburn, or erythema, is a common and familiar result of UV exposure. Recurrent and severe sunburns have been identified as risk factors for development of nonmelanoma skin cancer.Correct application of an effective sunscreen can reduce or prevent development of erythema. Avoidance of sunburn when using sunscreen, may well prolong the duration of recreational sun exposure among users.If a sunscreen with poor UV A protection is used in this manner, it would theoretically serve to increase UV A exposure. UV A has been shown in both human and animal model systems, to accelerate skin photoaging and cause skin can-cer.Reduction of time in the sun, and covering up with clothing, in combination with use of a sunscreen with good UV A protection, makes this less likely.
对应中文
晒伤或红斑是紫外线照射常见的结果。反复和严重晒伤已被确定为非黑色素瘤皮肤癌发生的危险因素。正确使用有效的防晒霜可以减少或预防红斑的发生。使用防晒霜时避免晒伤，可能会延长使用者休闲晒太阳的时间。如果UVA防护效果差的防晒霜以这种方式使用，理论上会增加UVA暴露。UVA已在人类和动物模型系统中显示，可加速皮肤光老化并导致皮肤老化。减少在阳光下的时间，用布遮盖，再加上使用具有良好UVA防护的防晒霜，这种情况不太可能发生。
英文原文
Study results differ with regard to the extent to which sunscreens protect against the immunosuppressive effect of UV radiation. UVB and to a lesser extent UVA radiation, even at suberythemogenic doses, impair epidermal Langerhans cell function causing immunosuppression, confined primarily to the skin. A single exposure can cause immunosuppression lasting 7 to 14 days. This plays a promotional role in the development of skin cancers. Some studies indicate little or no protection from sunscreen in preventing localized or systemic UV-induced suppression of contact hypersensitivity to nickel,while others indicate that even with suberythemal doses of UV, immune protection was provided by sunscreens.Methodological differences in these studies account for some of the variable conclusions drawn. Agreement lies in the recognition that both UVA and UVB portions of the spectrum contribute to immunosuppression, and that the dose of UV causing immunosuppression is less than the dose required to develop sunburn, both with and without sunscreens.This again emphasizes the importance of further development of sunscreens that protect against both UVB and UV A wavelengths, and argues for the use of a sunscreen with SPF of at least 15.
对应中文
关于防晒霜对紫外线的免疫抑制作用的保护程度，研究结果各不相同。UVB和较小程度的UVA辐射，即使是亚红斑剂量，也会损害表皮朗格汉斯细胞的功能，导致免疫抑制，主要局限于皮肤。单次接触可导致持续7至14天的免疫抑制。这对皮肤癌的发展起到了促进作用。一些研究表明，防晒霜对预防局部或系统性紫外线诱导的镍接触超敏反应的抑制作用很小或没有保护作用，而其他研究表明，即使在红斑以下剂量的紫外线下，防晒霜提供了免疫保护。这些研究中的方法差异解释了一些可变结论。共识在于认识到光谱中的UVA和UVB部分都有助于免疫抑制，并且无论有没有防晒霜，引起免疫抑制的紫外线剂量都小于发生晒伤所需的剂量。这再次强调了进一步开发同时抵御紫外线和UVA波长的防晒霜的重要性，并主张使用SPF值至少为15的防晒霜。
英文原文
Reassuringly, human studies are now indicating what previously was demonstrated in animal models. A number of studies showed that regular sunscreen application can delay or prevent development of skin cancers in mice.Two studies established that high SPF sunscreen reduces the number of new pre- cancerous solar keratosis and increases remission of preexisting solar keratosis.More recently Green et al.concluded that SPF 15-plus sunscreen use leads to a reduction in recurrent squamous cell carcinomas over a 4.5 year period. The same study showed no benefit of dietary supplementation with betacarotene in preventing skin cancers.
对应中文
令人欣慰的是，人类研究现在表明，动物模型已经证明了这一点。许多研究表明，定期使用防晒霜可以延缓或预防小鼠皮肤癌的发生。两项研究证实，高SPF防晒霜可以减少新的癌前日光角化病的数量，并增加已有日光角化病的缓解。最近，Green等人得出结论，使用SPF15以上的防晒霜可以在4.5年内减少复发的鳞状细胞癌。同一项研究表明，饮食中补充β-胡萝卜素对预防皮肤癌没有好处。
Efficacy
功效
英文原文
Questions have been raised regarding recommendations of application density or how much sunscreen should be applied when evaluating SPF. Regulations specify that sunscreens must be tested at an application density of 2mg or 2 μl/cm2.This translates into 35ml per application to adequately cover 1.73m2, the average adult body surface area.Not surprisingly the actual amount of sunscreen used by the consumer falls well short of that recommended. Study figures of the actual amount of sunscreen used in real life situations range from 0.5 mg/cm2 to 1.3 mg/cm2.Stenberg and Larko found that using half the recommended amount of sunscreen halves the SPF, but others have indicated that a significant decrease in protection may only occur with higher SPF sunscreens. Gottleib et al. applied half the recommended thickness of five sunscreens with SPFs of 4, 8, 10, 15 and 29. They found no significant change in measured SPF, other then the sunscreen of SPF 29.In practice, sunscreens are applied haphazardly, often providing minimal or no protection to hairy skin or areas of the body that are hard to reach.
对应中文
在评估SPF时，关于涂抹密度或防晒霜应该涂抹多少的建议，已经提出了一些问题。法规规定，防晒霜必须在2mg或2μl/cm²的涂抹密度下进行测试。这意味着每次涂抹35ml，足以覆盖1.73m²，即成人的平均体表面积。消费者使用的防晒霜的实际数量远远低于推荐值，这一点毫不奇怪。在现实生活中实际使用的防晒霜量的研究数据范围为0.5 mg/cm²至1.3 mg/cm²。Stenberg和Larko发现，使用推荐量的一半防晒霜会使SPF减半，但其他人指出，只有SPF较高的防晒霜才能显著降低防护效果。Gottleib等人使用了5种防晒霜推荐厚度的一半，SPF分别为4、8、10、15和29。他们发现，除了防晒系数为29的防晒霜外，测量的防晒系数没有显著变化。在现实中，防晒霜涂得很随意，通常对多毛的皮肤或身体难以触及的区域提供的保护微乎其微或根本不起作用。
英文原文
What is the optimal sun protection factor? Studies indicate significantly higher protection from SPF 30 products,which, with improved formulation, are now manufactured with lower percentages of sunscreen active ingredients, and hence less irritation.Higher SPF products are more likely to have good UV A protection and give some margin for error if under applied. The use of higher SPF sunscreens (over SPF 30, and up to SPF 100 in Japan), in vogue in the 1980s and early 1990s, are rarely needed outside of a population with abnormal response to UV radiation, such as those with impaired immune systems or photodermatoses. The American Academy of Dermatology Consensus Statement on Photoaging/Photodamage as a Public Health Concern, recommends that a maximally protective sunscreen (SPF 15 or higher) be applied under most conditions. These recommendations should be modified according to skin phenotype and sun exposure of the individual.
对应中文
最佳防晒系数是多少？研究表明，SPF30产品的防晒效果明显更好，这些产品经过改进配方后，现在生产的防晒活性成分的百分比更低，因此辐射也更少。更高的SPF产品更有可能具有良好的UVA保护作用，如果使用不足，会产生一定的误差。20世纪80年代和90年代初流行的高防晒系数防晒霜（防晒系数超过30，日本防晒系数高达100）在对紫外线辐射有异常反应的人群之外很少需要，例如免疫系统受损或光性皮肤病。美国皮肤病学会关于光老化/光损伤作为公共卫生问题的共识声明，建议在大多数情况下使用最大限度保护防晒霜(SPF 15或更高)。这些建议应该根据个人的皮肤表型和日照情况进行修改。
英文原文
The substantivity of a sunscreen is an indication of how well it maintains its advertised degree of protection under adverse con- ditions, such as swimming or sweating. The water resistance of sunscreens vary according to the formulation used.The FDA defined the meaning of terms such as ‘water resistant’ and ‘water- proof’.A sunscreen that retains its protective properties for 40 minutes in water, can be called water resistant. A waterproof sunscreen should retain these properties for 80 minutes of water exposure. While this served to establish labeling criteria within the industry, it may also serve to mislead consumers about the limits of sunscreen protection. Certain studies indicate no significant difference between the substantivities of water resistant and waterproof products; however, both had significantly better substantivity than products which made no claims regarding water resistance.As it stands, the public must still be encouraged to reapply sunscreens every 2 to 3 hours and after swimming.
对应中文
防晒霜的实质性程度表明，它在游泳或出汗等不利条件下，仍能很好地保持其宣传的保护程度。防晒霜的耐水性根据所用配方的不同而不同。FDA定义了“耐水”和“防水”等术语的含义。在水中保持40分钟保护性的防晒霜可以称为耐水。防水防晒霜应在暴露于水的80分钟内保持这些特性。虽然这在行业内建立了标签标准，但它也可能在防晒霜保护的限度上误导消费者。某些研究表明，防水产品和防水产品的质量没有显著差异；然而，这两种产品的耐水性都要比那些没有提出耐水性要求的产品要好得多。目前，我们仍必须鼓励公众每隔2到3小时以及游泳后重新涂抹防晒霜。
英文原文
The increasing evidence that UVA contributes to photoaging and photocarcinogenesis,has prompted much work aimed at establishing and quantifying the UVA protection factor of sunscreens. Again the marketing language can be misleading. The term ‘broad spectrum’ can be used for sunscreen which filters UV A II light, but fail to block in the longer wavelengths of UV A I.Standardization of methods used to measure UV A protection and the introduction of a universally agreed grading system for UV A protection are both urgent requirements.The star system has been adopted by certain companies denoting one star for poor UVA protection and four stars for good UVA protection. This is an in vitro method, involving a measure of the transmission of UV through ‘transpore’ tape.UV A leads to increased pigmentation of the skin in Fitzpatrick skin types III and IV. Persistent pigment-darkening is an in vivo method whereby the persistent pigment colour change of human skin, 1 hour after UV A radiation exposure, is measured.Again, knowledge of the action spectra for biologically relevant end-points, such as photoimmuno- suppression and the action spectrum for malignant melanoma, is necessary before recommending either method.
对应中文
越来越多的证据表明UVA有助于光老化和光致癌，这促使了许多旨在建立和量化防晒霜的UVA保护因子的工作。同样，营销语言可能具有误导性。“广谱”一词可以用来指能过滤UVA II光，但不能阻挡较长波长UVA I的防晒霜。标准化测量UVA防护的方法和引入普遍认可的UVA防护分级系统都是迫切需要的。某些公司已经采用了星形系统，表示一颗星的UVA防护效果差，四颗星的UVA防护效果好。这是一种体外方法，涉及通过“Transpore”胶带测量紫外线的传输。紫外线A导致FitzpatrickⅢ型和IV型皮肤色素沉着增加。持续性色素变暗是一种活体方法，通过这种方法可以测量人体皮肤在UVA照射后1小时的持续性色素颜色变化。同样，在推荐任何一种方法之前，有必要了解生物相关终点的作用光谱，如光免疫抑制和恶性黑色素瘤的作用光谱。
REFERENCES
1.Moloney, F. J., et al. (2002). “Sunscreens.” American Journal of Clinical Dermatology 3(3): 185-191.