防晒 | GPT 医学

防晒在晚春、盛夏、初秋是一件要紧事,然而我总觉得自己对防晒是一窍不懂——比如“防晒是不是防住直射阳光就行了”——所以花了几个小时学习了一下普通人一辈子也不会思考、学习、掌握的知识

结论和我的推论

  1. 防晒是不是只要防住直射阳光就行了?
    • 不是。紫外线漫反射挺多的。阴天没有直射阳光,紫外线指数也还是有 5 级左右。
  2. 防晒霜、楼阴、树荫、阳伞、其他衣物帽子,使用上有没有个优先级和基本法?
    • 结合使用,越多越好。“正确使用”的防晒霜好于其他,但防晒霜一般都不会被正确使用。推荐组合防晒:防晒霜 + 物理防晒。有效度:楼阴 > 密集树荫 > 阳伞。
  3. 阴天并没有直射阳光啊,哪儿都不晒,那要怎么防“晒”呢?
    • 阴天的紫外线大概率来源于漫反射。请继续防晒霜 + 穿衣阳伞帽子等。(但阳伞和帽子的效果会减弱。)
  4. 不晒太阳怎么补维生素 D(和钙)?
    • 维生素片(钙片)或者食物。完全没必要故意在 UVI 大于 5 的艳阳下暴晒来补。
  5. 什么是 SPF?
    • SPF 为 x 即为(UVB 的)晒伤时间延长 x 至倍。参考晒伤时间表。
      UV 指数 晒伤风险 晒伤时间
      0-2 60 分钟
      3-5 中等 45 分钟
      6-7 15-25 分钟
      8-10 很高 10-15 分钟
      11+ 极高 小于 10 分钟

喜闻乐见的 GPT 软文

作者:GPT(与我)

防晒是保护皮肤免受紫外线伤害的重要措施。随着人们对皮肤健康意识的提高,防晒已成为日常护肤的必要步骤。然而,许多人对防晒知识了解不足,导致选择不当或不合适的防晒产品,甚至完全不使用防晒,给皮肤健康带来潜在风险。本文将科普防晒的相关知识,帮助读者更好地了解防晒的重要性以及正确的使用方法。

一、紫外线的危害

太阳发出的紫外线(UV)是皮肤健康的主要威胁之一。UV 辐射可以分为 UV-A、UV-B 和 UV-C 三种。UV-C 被地球大气层吸收,不会对皮肤产生影响。UV-A 和 UV-B 是我们所面临的主要问题。

UV-A是一种长波紫外线,穿透力强,可深入皮肤内层,破坏皮肤胶原蛋白和弹性蛋白,导致皮肤老化和皱纹。UV-A 还可激活自由基,导致细胞膜的氧化损伤,增加皮肤癌的风险。

UV-B 是一种短波紫外线,对皮肤表层影响较大,会导致皮肤红肿、晒伤和皮肤癌。

二、如何选择合适的防晒产品

选择合适的防晒产品是防晒的关键。以下是一些选择防晒产品时应考虑的因素:

SPF 值:SPF 代表防晒剂的紫外线防护因子。SPF 值越高,保护效果越好。通常建议选择 SPF 值在30-50 之间的产品。但是,高SPF值并不一定意味着更好的保护。SPF50 的产品可防御 98% 的紫外线,而 SPF100 的产品仅比 SPF50 高出 1% 的防御率,而且其价格更贵。SPF 只包含对 UV-B 的保护能力,不包含对 UV-A 的保护能力。

PA值:PA 代表对 UVA 的防护能力。PA+ 表示对 UV-A 的保护能力低,PA++++ 表示对 UV-A 的保护能力强。选择 PA++++ 的产品能更好地防止皮肤老化和皮肤癌。

防水:如果您在游泳或运动,防晒产品需要有防水功能,防止流失。

三、如何正确使用防晒产品

选择适合自己的防晒产品后,正确使用防晒也非常重要。以下是一些使用防晒产品的技巧:

适量使用:一般建议使用约 1/4 到 1/3 茶匙的防晒产品来涂抹脸部,大约 1 盎司(30毫升)的防晒产品来涂抹全身。使用不足可能无法完全保护皮肤,使用过多可能会导致不透气或起皮。

均匀涂抹:将防晒产品均匀涂抹在皮肤上,包括眼周和嘴唇周围。不要在皮肤上留下任何未覆盖的区域。

重复使用:防晒产品在皮肤上的保护时间有限,需要在出汗、游泳或用毛巾擦拭后再次涂抹,以确保持续保护。

避免阳光暴晒时段:尽可能避免在阳光最强烈的时段(通常为早晨10点至下午4点)暴露在阳光下。

四、其他注意事项

除了选择合适的防晒产品和正确使用外,以下是一些其他需要注意的事项:

避免使用过期的防晒产品,过期的产品可能已失去其防晒效果。

不要依赖防晒产品完全保护您的皮肤。穿上透气的长袖衣服、帽子和太阳镜可以提供额外的保护。

如果您的皮肤对防晒产品敏感或容易出现过敏反应,请选择温和的防晒产品,并在使用前进行测试。

总之,防晒是保护皮肤免受紫外线伤害的关键措施。正确选择和使用防晒产品可以帮助保护皮肤免受晒伤、皮肤老化和皮肤癌等问题的影响。请注意选择合适的防晒产品和正确使用防晒产品,以保护您的皮肤健康。

随意的正文

我感觉“防晒”最大的误区可能正是源于“防晒”这个词本身,要防的应该不是晒,而是紫外线(简称 UV)本身:

  • UV 弱的时候在阳光直射下可能也没事。
  • UV 强的时候,可能在树荫、楼阴下也有事。

于是花了点时间学习了一下防晒的周边概念。这里会谈论到 SPF、UPF、防晒霜、阳伞、树荫、紫外线指数等。

这里只写一些自己的学习心得,学习材料放在附录里。

这些或多或少是已有资料:

  1. 由于 SPF 本身只度量 UVB,所以我猜测各防晒产品(如果真的良心做了实验的话也)都是实验室用纯 UVB 测出来的。
  2. 一篇文章说“如果防晒霜被正确地使用以预防晒伤,那么不需要使用高于 15 的防晒系数 (3)”。这很容易理解,SPF 15 可以延长晒伤时间 15 倍,即使是 UVI 10 的大中午,也可以防护 150~225 分钟,切推荐每 2 小时重新涂抹防晒霜,这确实足以防护。
  3. 但大可放心,防晒霜不可能基本正确使用的:“由于人类行为的不确定性,实际上达到的保护程度通常不超过无保护时的 10 倍。穿着衣服通常更有效,近 90% 的夏季服装提供超过 10 倍的保护,并提供与防晒霜 SPF 30 或更高的等效保护。”
  4. 晴天的树荫和楼阴下、阴天的所有室外确实都有紫外线。其中有一部分来自漫反射,而阴天的漫反射成分显然更多。漫反射的紫外线并不总是从上朝下的,也有横向的漫反射。我认为阳伞、帽子显然只能遮挡垂直方向的紫外线,而无法遮挡水平方向的紫外线,我认为阴天里水平方向漫反射的紫外线比晴天更多,因此我认为在阴天里更应该使用防晒霜。
  5. 稀稀拉拉的树荫作用不大,要寻找遮天蔽日的密集树叶带来的树荫:如果有 90% 的天空遮盖率,那么所有纬度都可能获得 UPF 为 10 的紫外线防护。
  6. (下面)文 1 对比的是 SPF 100 的防晒霜和阳伞,结论显示阳伞远不如防晒霜,以及 SPF 100 也无法保证暴晒 3.5 小时后没有晒伤。现实中 SPF 100 的产品还是很少见的,因此混合防晒即为重要。

而下面这个就是个人的奇葩研究了。

虽说 UPF 和 SPF 没有换算关系,然而我感觉在简化的情况下 UPF 和 SPF 基本可以等价。

  • 我感觉 UPF 差不多代表过滤率为 。我没查详细的公式,就是根据表中的几个散点这么感觉的。
  • 那么如果我们选择一个非常简化的模型,例如只考虑 UVB,以及相信如果 的 UVB 被过滤的话,皮肤晒伤时间就变长 倍。
  • 那么对于 UPF 为 x 的物品,它对应的 SPF便也还是

这样的话,UPF 和 SPF 指数基本是等价的。现实中各指数在 15 以上时似乎确实也是基本等价的。

演算示例:UPF 为 10,算出过滤率为 ,即 90% 被过滤。接下来有,即 SPF 也是 10。

研究的有用性示例 1:如果说阳伞下也还有 的紫外线,那么阳伞就过滤了 85% 的紫外线,真实 UPF 就是 ,能延长晒伤时间 6.67 倍。

研究的有用性示例 2:足够的树荫的过滤率为 95%,那 UPF 就有 20,可以延长晒伤时间 20 倍。而阳伞、树荫等在一次使用中不存在涂抹量不达标、损耗等情况,看起来还是靠谱的。不过那个论文的实验数据的 UVI 整体很低,不知道会不会有很大的精确度影响。

学习材料

SPF 和 UPF

SPF代表“防晒系数”,它测量了皮肤暴露在阳光下变红所需的时间。它是衡量防晒霜保护皮肤免受紫外线B(UVB)辐射的能力的指标,这是晒伤的主要原因。防晒霜的SPF值越高,保护效果越好。例如,SPF 30表示皮肤开始变红所需的时间比没有涂防晒霜时长30倍¹⁴。

UPF代表“紫外线保护因子”,它测量了穿着衣物时紫外线辐射穿透织物并到达皮肤的量。它是衡量衣物保护皮肤免受紫外线辐射的能力的指标。UPF值越高,保护效果越好。例如,具有UPF评级50的衬衫只允许1/50的紫外线辐射穿透¹³。

要测量SPF,人们将防晒霜涂在皮肤上,然后将皮肤暴露在紫外线辐射下。测量涂有和未涂有防晒霜时皮肤开始变红所需的时间。这两个时间之比就是SPF值¹。

要测量UPF,将织物样品暴露在紫外线辐射下,然后测试通过织物样品的紫外线辐射量。通过织物样品的紫外线辐射量与样品接收到的总紫外线辐射量之比就是UPF值¹。

注意,SPF 只考虑 UVB,而 UPF 考虑 UVA 和 UVB

SPF stands for “Sun Protection Factor” and measures the amount of time it takes for sun-exposed skin to redden. It is a measure of how well sunscreen protects skin from UVB rays, which are the primary cause of sunburn. The higher the SPF number, the greater the protection. For example, an SPF of 30 means that it will take 30 times longer for skin to start turning red than it would without sunscreen¹⁴.

UPF stands for “Ultraviolet Protection Factor” and measures the amount of UV radiation that penetrates a fabric and reaches the skin. It is a measure of how well clothing protects skin from UV radiation. The higher the UPF number, the greater the protection. For example, a shirt with a UPF rating of 50 allows only 1/50th of UV radiation to penetrate through it¹³.

To measure SPF, a person applies sunscreen to their skin and then exposes their skin to UV radiation. The amount of time it takes for their skin to start turning red is measured with and without sunscreen. The ratio of these two times is the SPF number¹.

To measure UPF, a fabric sample is exposed to UV radiation and then tested for how much UV radiation passes through it. The ratio of UV radiation that passes through the fabric sample to the total amount of UV radiation that hits the sample is the UPF number¹.

Source: Conversation with Bing

  1. What’s the Difference Between SPF and UPF? - Respect The Sun.
  2. What Does the SPF Number on Sunscreen Mean? - Verywell Health.
  3. Is There A Difference Between SPF & UPF? - Sunscreen.
  4. What is UPF? A guide to UPF clothing - Reviewed.
  5. Sun Protective Clothing - The Skin Cancer Foundation.

SPF 和 UPF 没有明确的换算关系。UPF 是对衣物等来说的,统计紫外线透过率;SPF 是对人来说的,统计晒伤时间。

但有一些数据可以参考

SPF % UVB 阻挡(吸收)
2 50%
4 75%
15 93.3%
30 96.7%
50 98.0%
UPF % UVA 和 UVB 阻挡
15-24 93.3% 到 95.9%
25-39 96.0% 到 97.4%
40-50+ 97.5%+

数据来源:UPF and SPF Explained

表格制作:GPT。

紫外线指数与晒伤时间

UV 指数 晒伤风险 晒伤时间
0-2 60 分钟
3-5 中等 45 分钟
6-7 15-25 分钟
8-10 很高 10-15 分钟
11+ 极高 小于 10 分钟

数据来源 UV Index: The Sun Safety Scale

表格制作:GPT。

文 1 摘要

重要性:防晒行为对预防皮肤癌有影响。阴凉处能通过物理遮挡皮肤,使其免受直接有害紫外线的伤害,但皮肤仍可能暴露在反射和间接的紫外线下。目前没有标准指标来评估阴凉处在防晒保护中的有效性,临床证据不足,不能证明仅靠海滩遮阳伞就能提供足够的防晒保护。

目标:在实际使用条件下,直接测量标准海滩遮阳伞提供的防晒保护与高防晒因子的防晒霜所提供的防晒保护的差异。

设计、环境和参与者:在德克萨斯州Lewisville湖(海拔159米)于2014年8月13日至15日,对81名Fitzpatrick肤色类型为I(n = 1)、II(n = 42)和III(n = 38)的参与者进行了单中心、评估者盲目、随机的临床研究。参与者被随机分配到2组:一组仅使用海滩遮阳伞,另一组仅使用防晒因子为100的防晒霜。所有参与者在正午时分的阳光海滩上呆了3个半小时。对每个个体暴露在阳光下的所有暴露部位进行临床晒伤评估,时间为晒后22至24小时。

干预措施:海滩遮阳伞提供的阴影或防晒因子为100的防晒霜提供的保护。

主要结果和指标:晒后22至24小时所有暴露部位的晒伤情况。

结果:在81名参与者(25名男性和56名女性;平均[SD]年龄为41 [16]岁)中,对所有评估的身体部位(脸部,颈后,上胸部,手臂和腿部),遮阳伞组与基线相比显示出明显的临床晒伤评分增加,并且较防晒霜组在暴露后全局评分更高(0.75比0.05;P < 0.001)。遮阳伞组共发生142次晒伤,防晒霜组为17次。41名遮阳伞组参与者中的32人(78%)在1个或多个部位出现红斑,防晒霜组的40名参与者中有10人(25%)出现红斑(P < 0.001)。遮阳伞或防晒霜单独使用均不能完全防止晒伤。

结论和意义:单独使用遮阳伞可能无法提供足够的防护来抵御长时间的紫外线暴露。重要的是要教育公众,组合多种防晒措施可能需要以达到最佳的防护效果。

Importance: Sun-protective behavior affects skin cancer prevention. Shade works by physically shielding skin from direct harmful UV rays; however, skin may still remain exposed to reflected and indirect UV rays. There is no current standard metric to evaluate shade for its effectiveness in sun protection, and there is insufficient clinical evidence that a beach umbrella alone can provide adequate sun protection.

Objective: To directly measure sunburn protection offered by a standard beach umbrella compared with that provided by sunscreen with a high sun protection factor under actual use conditions.

Design, setting, and participants: A single-center, evaluator-blinded, randomized clinical study was conducted from August 13 to 15, 2014, in Lake Lewisville, Texas (elevation, 159 m above sea level), among 81 participants with Fitzpatrick skin types I (n = 1), II (n = 42), and III (n = 38). Participants were randomly assigned to 2 groups: 1 using only a beach umbrella, and the other using only sunscreen with a sun protection factor of 100. All participants remained at a sunny beach for 3½ hours at midday. Clinical sunburn evaluation of each individual for all exposed body sites was conducted 22 to 24 hours after sun exposure.

Interventions: The shade provided by a beach umbrella or protection provided by sunscreen with a sun protection factor of 100.

Main outcomes and measures: Sunburn on all exposed body sites 22 to 24 hours after sun exposure.

Results: Among the 81 participants (25 male and 56 female; mean [SD] age, 41 [16] years) for all body sites evaluated (face, back of neck, upper chest, arms, and legs), the umbrella group showed a statistically significant increase in clinical sunburn scores compared with baseline and had higher postexposure global scores than the sunscreen group (0.75 vs 0.05; P < .001). There was a total of 142 sunburn incidences in the umbrella group vs 17 in the sunscreen group. Thirty-two of the 41 participants (78%) in the umbrella group showed erythema in 1 or more sites vs 10 of the 40 participants (25%) in the sunscreen group (P < .001). Neither umbrella nor sunscreen alone completely prevented sunburn.

Conclusions and relevance: A beach umbrella alone may not provide sufficient protection for extended UV exposure. It is important to educate the public that combining multiple sun protection measures may be needed to achieve optimal protection.

来源:国家医学图书馆
翻译:GPT

Ou-Yang H, Jiang LI, Meyer K, Wang SQ, Farberg AS, Rigel DS. Sun Protection by Beach Umbrella vs Sunscreen With a High Sun Protection Factor: A Randomized Clinical Trial. JAMA Dermatol. 2017 Mar 1;153(3):304-308. doi: 10.1001/jamadermatol.2016.4922. PMID: 28114650.

文 2 摘要

紫外线(UV)辐射与负面的健康影响有关,包括阳光伤害和皮肤癌。这项研究的目的是比较太阳伞和树所提供的阴凉处的保护作用。记录紫外线辐射水平和剂量的太阳传感器被放置在阴凉处和阳光直射处。在加利福尼亚州萨克拉门托,在中午12:30和下午3:00之间,每半小时记录一次测量结果。结果表明,树荫下的紫外线辐射水平不是零。位于树荫下的传感器表明,在树荫下检测到超过5%的紫外线辐射。位于太阳伞阴凉处的传感器显示,有超过17%的紫外线辐射到达阴凉处。我们研究中使用的太阳传感器收集了与紫外线指数有关的紫外线辐射数据;然而,它们没有区分UVA、UVB、可见光和红外线。在树荫下检测到的紫外线辐射量不是零,因此应定期使用防晒霜和其他防晒措施,以减少阳光伤害和皮肤癌的风险。

Ultraviolet (UV) radiation is associated with negative health effects, including sun damage and skin cancer. The purpose of this study is to compare the protective effects of the shade provided by a sun umbrella versus that provided by a tree. Sun sensors that register the level and dose of UV radiation were placed in the shade and in direct sunlight. Measurements were recorded every half hour between the hours of 12:30 p.m. and 3:00 p.m. in Sacramento, California. The results suggest that the level of UV radiation in the shade is not zero. The sensors located in tree shade indicated that over 5% of UV radiation was detected in the shade. The sensors located in sun-umbrella shade showed that greater than 17% of UV radiation reached the shade. The sun sensors used in our study collected UV radiation data relevant to UV index; however, they did not differentiate between UVA, UVB, visible, and infrared light. The amount of UV radiation detected in the shade is not zero, thus regular sunscreen use and other sun protective practices should be followed to reduce the risk of sun damage and skin cancer.

来源:国家医学图书馆
翻译:GPT

Saric-Bosanac SS, Clark AK, Nguyen V, Pan A, Chang FY, Li CS, Sivamani RK. Quantification of ultraviolet (UV) radiation in the shade and in direct sunlight. Dermatol Online J. 2019 Jul 15;25(7):13030/qt4wc0f6tw. PMID: 31450273.

文 3 摘要

防止过度暴露在阳光下的技巧包括使用防晒霜、穿着防护服装和寻找遮蔽处。使用防晒霜的局部方法可能存在问题,由于人类行为的不确定性,实际上达到的保护程度通常不超过无保护时的10倍。穿着衣服通常更有效,近90%的夏季服装提供超过10倍的保护,并提供与防晒霜SPF 30或更高的等效保护。然而,显然衣服的限制在于只有覆盖的部位受到保护。

寻找遮蔽处可能是减少整个身体暴露于太阳紫外线(UV)辐射的有效方法,前提是阻挡了天空的重要部分和直接阳光,以衰减直接和散射的UV辐射。树提供了一种自然的遮蔽手段,但属于不同属和树冠尺寸的多样性可能会使得泛化提供的保护程度困难。虽然之前的研究采用系统化方法来测量树荫所提供的保护,但大部分研究都包含了大量数据(例如UV传感器相对于太阳的方向、离地高度等),难以将所提供的结果与不同树种下的典型保护程度联系起来。本文的方法是在摄影中展示一系列常见的英国树种,并在一个夏日中午左右的背景下测量防晒保护。

SIR, Techniques for preventing overexposure to sunlight include sunscreens, clothing and shade. Topical approaches using sunscreens can be problematic and the vagaries of human behaviour are such that the protection achieved in practice is frequently no greater than 10‐fold of that using no protection. Clothing is generally more effective, with almost 90% of summer clothing offering more than 10‐fold protection and providing equivalent protection to sunscreens of sun protection factor 30 or higher. The obvious limitation with clothing, however, is that only covered sites are protected.

Seeking shade can be an effective way of reducing exposure of the whole body to solar ultraviolet (UV) radiation, provided that a significant part of the sky is blocked, as well as direct sunlight, in order to attenuate both direct and scattered UV radiation. Trees provide a natural means of shade, but the diversity of genus and tree canopy dimensions can make it difficult to generalize the degree of protection afforded. While previous studies have taken a systematic approach to measuring the protection afforded by tree shade,most of them have contained such a large number of data (e.g. orientation of UV sensor with respect to the sun, height above ground etc.) that it can be difficult to relate the results presented to a feeling for the typical protection provided under different varieties of trees. The approach here has been to illustrate photographically a range of common British trees and to measure sun protection in the context of someone seeking shade around the middle of a summer’s day.

来源:Oxford Academic
翻译:GPT

B.L. Diffey, J.L. Diffey, Sun protection with trees, British Journal of Dermatology, Volume 147, Issue 2, 1 August 2002, Pages 397–398, https://doi.org/10.1046/j.1365-2133.2002.483010.x

文 4 摘要

树木会影响到行人所受到的太阳紫外线辐射量。研究人员开发了一个三维模型,用于预测树冠间距等于或大于个别树冠宽度的树冠间的紫外-B(UV-B)辐射场。该模型预测了在晴朗天气下,无论是在阳光下还是在阴影下的相对辐射强度(以上方辐射强度为分母),平均偏差误差小于0.01,均方根误差为0.07。模型和测量结果都显示,人们通常感觉到的环境中低辐射强度的阴凉地方实际上可能存在明显的UV-B暴露(相当于直接阳光下的40-60%)。对于6月和7月中午前后4小时,模拟了住宅区树木覆盖率与儿童和成人皮肤红斑性UV-B暴露之间的关系。结果显示,在位于15度和30度纬度的城市中,人类暴露(水平方向)几乎相同。对于15到60度之间的纬度,树木覆盖率低于50%时,紫外线防护因子(UPF)小于2。对于90%的树木覆盖率,所有纬度都可能获得UPF为10的紫外线防护。

Trees influence the amount of solar UV radiation that reaches pedestrians. A three-dimensional model was developed to predict the ultraviolet-B (UV-B) irradiance fields in open-tree canopies where the spacing between trees is equal to or greater than the width of individual tree crowns. The model predicted the relative irradiance (fraction of above-canopy irradiance) under both sunlit and shaded conditions under clear skies with a mean bias error of less than 0.01 and a root mean square error of 0.07. Both model and measurements showed that the locations people typically perceive as shady, low-irradiance locations in the environment can actually have significant UV-B exposure (40-60% of that under direct sunlight). The relationship of tree cover in residential neighborhoods to erythemal UV-B exposure for children and adults was modeled for the 4 h around noon in June and July. Results showed that human exposures (on the hor-izontal) in cities located at 15 and 30° latitudes are nearly identical. For latitudes between 15 and 60°, ultraviolet protection factors (UPF) were less than 2 for less than 50% tree cover. A UPF of 10 was possible at all latitudes for tree cover of 90%.

摘要补足 The sky view for the below-canopy measurement locations varied hm 0.05 to 0.84 for measurements made near a single tree (Table 1 ) and from 0.10 to 0.66 for measurements made in the tree grove (Table 2).

摘要补足 Modeled relationship between tree cover and sky view. 近似线性关系,给出几个点的大致值(肉眼估算)

Mean skyview Tree cover fraction
1 0
0.8 0.1
0.5 0.3
0.3 0.5
0.1 0.8
0 1

来源:Wisley Online Library
文字识别:iOS
翻译:GPT

Grant, R.H., Heisler, G.M. and Gao, W. (2002), Estimation of Pedestrian Level UV Exposure Under Trees. Photochemistry and Photobiology, 75: 369-376. https://doi.org/10.1562/0031-8655(2002)0750369EOPLUE2.0.CO2

文 5 摘要

本文介绍了亚热带南半球纬度下树荫处漫反射红斑紫外线(UV)和UV-A辐射的第一组定量数据。在夏季,树荫下约60%的红斑紫外线辐射是由漫反射成分引起的。同样,树荫下大约56%的UV-A辐射是由漫反射成分引起的。在树荫下,这些漫反射UV百分比从早晨到中午到下午相对稳定。相比之下,在阳光下,漫反射UV的百分比从早上到中午再到下午都有所降低。在东部标准时间9:00至15:00之间,在水平面上,树荫下的漫反射UV暴露量约为4MED(最小红斑剂量)和 ,分别是红斑紫外线和UV-A的辐射量。树荫中的高漫反射UV成分可能会导致不仅是水平面上的暴露部位受到高UV暴露,而且还可能导致未受UV保护的身体部位(包括眼睛和面部)同样受到高UV辐射

The first set of quantitative data of diffuse erythemal UV and UV-A radiation in tree shade at a sub-tropical Southern Hemisphere latitude is presented. Over the summer, approximately 60% of the erythemal UV radiation in tree shade is due to the diffuse component. Similarly, approximately 56% of the UV-A radiation in tree shade is due to the diffuse component. In tree shade these diffuse UV percentages are relatively constant from the morning to noon to afternoon periods. In comparison, in full sun, there is a decrease in the percentage of diffuse UV from morning to noon to afternoon. The exposures to diffuse UV on a horizontal plane in tree shade between 9:00 EST and 15:00 EST are of the order of 4 MED (minimum erythemal dose)and 14 J cm−2 for erythemal UV and UV-A, respectively. The high diffuse UV component in the shade may result in high UV exposures not only to unprotected parts of the body on a horizontal plane, but also in equally high UV irradiances to parts of the body, including the eyes and face, that are not UV protected.

来源:Elsevier
翻译:GPT

A.V. Parisi, M.G. Kimlin, J.C.F. Wong, M. Wilson,
Diffuse component of solar ultraviolet radiation in tree shade1Paper presented at the 2nd Online Conference for Photochemistry and Photobiology.1, Journal of Photochemistry and Photobiology B: Biology, Volume 54, Issues 2–3, 2000, Pages 116-120, ISSN 1011-1344,

文 6 摘要

本文介绍了对昆士兰州学童常用的3种帽子的紫外线(UV)保护结果。通过在多云和晴朗天气条件下,在每个旋转头模型上选择的解剖学位置放置16个聚硫酚剂量计来实现。通过这些实验,测量了面部分布和面部部位的红斑性UV暴露。提供了面部接受高UV暴露的总体图像,包括多云和晴朗大气条件下佩戴和不佩戴帽子的情况。本研究使用的三种帽子在多云条件下与晴朗条件下相比,平均测量点的紫外线保护因子(UPF)降低了22%、11%和13%。

This paper presents the results of the ultraviolet (UV) protection for 3 types of hats commonly used by Queensland schoolchildren This was achieved through using 16 polysulphone dosimeters placed at selected anatomical locations over each rotating headform during cloudy conditions compared to clear sky conditions. From these experiments, the facial distribution and erythemal UV exposure at facial sites were measured. The overall picture of the facial sites receiving high UV exposure was provided, both with and without hats for cloudy and clear atmospheric conditions. A reduction in the ultraviolet protection factor (UPF), averaged over all measurement sites of 22%, 11% and 13% compared to clear sky conditions occurred for the 3 hats used in this study when they were worn in cloudy conditions compared to clear sky conditions.

来源:PhotoBiology
翻译:GPT

Kimlin, M. G., and A. Parisi. "Ultraviolet protective capabilities of hats under two different atmospheric conditions." Vertex 100.100 (1999): 100.

然而好像没发表。