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  • When you go to buy sunscreen, you might look for one thing: SPF.


  • It stands for sun protection factor, and based on that name, it seems like it should tell you how well you'll be protected from the sun.


  • Exceptthat's not totally true.

    只是...... 這不完全正確。

  • Because while SPF might sound like a perfect, rational scientific unit, there are a lot of flaws in the way it's named and the way it's tested.

    因為,儘管 SPF 聽起來是個完美、合理的科學單位,它的命名及測試方式中存在著很多瑕疵。

  • So if you want to be as protected from the sun as possible, you're going to have to know a lot more than that one number.


  • First, as a disclaimer, it's worth noting that countries approach sunscreen regulations differently.


  • This episode is a good general overview, but keep in mind that things might be different where you live.


  • Okay, that being said, onward.


  • Essentially, SPF measures how much radiation is blocked from reaching your skin.

    基本上,SPF 測量有多少輻射被阻擋到達你的皮膚。

  • So if it's SPF 30, it will protect you against thirty times more exposure than if you didn't wear sunscreen.

    所以如果是 SPF 30,比起你沒有擦防曬乳的時候,它可以減少 30 倍的曝曬。

  • That translates to roughly 97% protection, and it explains why anything higher than SPF 30 isn't that much more effective.

    這大約等於百分之 97 的保護,也解釋了為什麼任何 SPF 30 以上的東西並不會更加有效。

  • SPF 50, for example, blocks fifty times the radiation, or 98% of it.

    比方說 SPF 50,阻擋 50 倍的輻射,或是百分之 98。

  • Which isn't that different.


  • Still, regardless of what that number says, SPF only tells you how protected you'll be from a specific type of radiation.

    不論這個數字代表什麼,SPF 只是告訴你,你會免於受到哪一種特定輻射的傷害。

  • The rating you see on sunscreen bottles is only required to show protection against UVB rays, the type of radiation that causes sunburns and leads to skin cancer.

    你在防曬乳瓶子上看到的分級只需要標示針對 UVB 射線的保護,這種輻射會造成曬傷並導致皮膚癌。

  • It doesn't have to show protection against UVA radiation, which causes wrinkles, premature skin aging, and again, skin cancer.

    它不需要標示針對 UVA 輻射的保護,這種輻射會造成皺紋、皮膚過早老化,以及皮膚癌。

  • So even if you're using SPF one thousand, that doesn't mean you're protected against UVA.

    所以就算你使用 SPF 一千,這並不代表你就可以防止 UVA。

  • If you want to avoid both kinds of rays, you'll need to look for broad-spectrum sunscreen.

    如果你想要避免這兩種輻射,你需要尋找 broad-spectrum 防曬乳。

  • Another thing worth knowing about SPF is that the way it's tested isn't bulletproof.

    另外一件關於 SPF 應該要知道的事情是,它受測試的方法並不完善。

  • To figure out how much UVB something blocks, you'd think scientists would use some sort of skin-like compound in a Petri dish.

    要釐清一個東西可以阻擋多少 UVB,你可能會以為科學家會用某種類似皮膚的化合物放進培養皿。

  • Like, just shine some light on this stuff, and see how much radiation gets through.


  • But while that is how they test broad-spectrum sunscreen, it isn't how they test SPF.

    儘管這是他們測試 broad-spectrum 防曬乳的方式,卻不是測試 SPF 的方式。

  • To get an SPF rating, researchers use volunteers.

    要得到 SPF 的分級,研究人員會找來自願者。

  • First, they shine a UV lamp on one spot on participants' bare backs to get a baseline for their tendency to burn.

    首先,他們將 UV 燈照射在受試者裸背上的一點以得到他們易曬傷程度的一個基準。

  • Then, a lab tech applies a gob of sunscreen to a different spot and allows it to dry.


  • Finally, the tech turns the UV light back on, and sees how much longer the participants last before turning red again.

    最後,測試人員再將 UV 燈打開,並觀察受試者的皮膚再經過多久才會變紅。

  • If they burned in four minutes unprotected, but 60 minutes with sunscreen, that earns an SPF fifteen rating.

    如果他們在沒有保護的情況下在 4 分鐘內曬傷,而在有擦防乳的時候,在 60 分鐘內曬傷,這樣就可以得到 SPF 15 的等級。

  • And if this process seems sketchy and full of issues


  • Yes.


  • Yes, it does.


  • For one, people turn red at different amounts of exposure.


  • So if you used a bunch of pale people in one study and a bunch of people with darker skin in another, you'd get totally different results.


  • And then there's the amount of sunscreen used in these tests.


  • While there's tons of variability between testers, protocol calls for no less than two milligrams of sunscreen per square centimeter of skin.


  • And that's significantly more than people tend to use in real life.


  • In one study, it was more than twice the amount.


  • Ultimately, these tests just aren't representative of what happens in the real world.


  • They don't take into account things like skin color, or how much sunscreen people actually use.


  • So when you're buying this stuff, it's probably worth keeping those things in mind.


  • For example, maybe this means it's worth putting on sunscreen more often than you currently do.


  • If nothing else, though, the good news is that researchers are at least aware that there's a problem here, and they've been working on protocols to hopefully get more consistent results.


  • Their ideas include using robots that spread sunscreen evenly in all conditions and shifting towards standardized in vitro testing using chemicals in a dishno human skin involved.

    他們的想法包含使用機器人在各種情況下將防曬乳均勻地噴灑,以及朝向標準化的體外測試,在培養皿中使用化學物質 - 不使用人類皮膚。

  • This will let scientists get way more data points and will improve accuracy.


  • At the end of the day, SPF can be a helpful way to understand what you're buying.

    不管怎麼說,SPF 可以幫助你理解你所購買的東西。

  • To make an informed decision, you just need to know what it says and where those numbers are coming from.


  • And it's also worth knowing that not all hope is lost, either.


  • Even if this is a bit of a flawed system, multiple studies have shown that consistent use of sunscreen, even at low SPF, reduces your risk of skin cancer.

    儘管這是個有點瑕疵的系統,許多研究都顯示,持續使用防曬乳,即便 SPF 數值很低,可以降低罹患皮膚癌的風險。

  • So, it's always worth lathering up!


  • If you've ever wished you just didn't have to wear sunscreenwell, I've got some sad news for you.


  • Almost all amphibians, reptiles, birds, and fish can make their own sunscreen.


  • Mammals are kind of the odd ones out.


  • If you want to learn more, you can watch our episode about the missing sunscreen gene after this.


When you go to buy sunscreen, you might look for one thing: SPF.


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B1 中級 中文 美國腔 輻射 曬傷 測試 保護 使用 皮膚

SPF 係數愈高愈好!? 專家告訴你防曬乳的真相!(SPF Doesn't Mean What You Think It Means)

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    Nina 發佈於 2019 年 09 月 26 日