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防晒霜上标的SPF是什么意思

SPF Doesn't Mean What You Think It Means

SPF究竟是什么意思?
When you go to buy sunscreen,
当你买防晒霜的时候
you might look for one thing: SPF.
你可能会找一个指标:SPF
It stands for sun protection factor,
它代表防晒指数
and based on that name, it seems like it should tell you how well you’ll be protected from the sun.
这个名字好像是告诉你产品的防晒效果如何
Except… that’s not totally true.
但这并不完全正确
Because while SPF might sound like a perfect, rational scientific unit,
虽然SPF听起来像是一个完美合理的科学单位
there are a lot of flaws in the way it’s named and the way it’s tested.
但是它的命名方式和试验方式有很多漏洞
So if you want to be as protected from the sun as possible,
因此如果你想防晒效果更好
you’re going to have to know a lot more than that one number.
你需要知道更多
First,as a disclaimer,
首先 作一个声明
it’s worth noting that countries approach sunscreen regulations differently.
值得注意的是 各国对防晒霜的规定有所不同
This episode is a good general overview,
指标是相对整体而言的
but keep in mind that things might be different where you live.
但请记住 不同国家依据的标准有所不同
Okey,that being said, onward.
好的 说到这里 继续
Essentially,SPF measures how much radiation is blocked from reaching your skin.
实际上 SPF衡量的是被阻隔在你皮肤外的辐射量
So if it’s SPF 30,
如果SPF为30
it will protect you against thirty times more exposure
那么与你不涂防晒霜时相比
than if you didn’t wear sunscreen.
涂防晒霜能阻挡30倍的辐射
That translates to roughly 97% protection,
这表示防晒霜大约能起97%的防晒作用
and it explains why anything
这就解释了为什么任何
higher than SPF 30 isn’t that much more effective.
SPF值高于30的防晒霜没有更明显效果
SPF 50, for example,
再比如说SPF为50
blocks fifty times the radiation,
可以阻挡50倍的辐射
or 98 % of it.
或者说98%的辐射
Which isn’t that different.
这并没有什么区别
Still,regardless of what that number says,
但是 不管SPF值是多少
SPF only tells you how protected you’ll be from a specific type of radiation.
它只能告诉你能免受多少特定类型的辐射
The rating you see on sunscreen bottles
你在防晒霜上看到的数值
is only required to show protection against UVB rays,
只显示了对UVB射线的防护效果
the type of radiation that causes sunburns and leads to skin cancer.
这种辐射会导致晒伤甚至引发皮肤癌
It doesn’t have to show protection against UVA radiation,
但是不代表能预防
which causes wrinkles, premature skin aging, and again, skin cancer.
可导致皮肤老化 皱纹 引发皮肤癌的UVA射线
So even if you’re using SPF one thousand,
因此 即使你用了SPF1000的防晒霜
that doesn’t mean you’re protected against UVA.
也不意味着能阻隔UVA的辐射
If you want to avoid both kinds of rays,
如果你想要避免这两种辐射
you’ll need to look for broad-spectrum sunscreen.
你需要用广谱防晒
Another thing worth knowing about SPF
你该知道另一件关于SPF的事是
is that the way it’s tested isn’t bulletproof.
它的测试方式并不是完美的
To figure out how much UVB something blocks,
为了算出有多少UVB会被阻挡
you’d think scientists would use some sort of
你可能认为科学家会在
skin-like compound in a Petri dish.
培养皿中用一些类似皮肤的化合物
Like,just shine some light on this stuff,
直接把它们放在光下
and see how much radiation gets through.
然后看有多少辐射穿过
But while that is how they test broad-spectrum sunscreen,
但是这是他们测试广谱防晒霜的方法
it isn’t how they test SPF.
而不是测试SPF的方法
To get an SPF rating,
研究人员通过志愿者测试
researchers use volunteers.
来得到SPF的数值
First,they shine a UV lamp
首先 他们将紫外线灯照在
on one spot on participants’bare backs
参与者裸露后背的一个点上
to get a baseline for their tendency to burn.
得到一个晒伤临界点的基础值
Then,a lab tech applies a gob of sunscreen
然后 实验人员会在不同地方
to a different spot and allows it to dry.
涂上防晒霜并等它变干
Finally,the tech turns the UV light back on,
最后 技术人员再次打开紫外线灯
and sees how much longer the participants last before turning red again.
观察参与者的皮肤经过多久会再次变红
If they burned in four minutes unprotected,
志愿者在没涂防晒霜时 四分钟就会晒伤
but 60 minutes with sunscreen,
而涂防晒霜后 可以坚持60分钟
that earns an SPF fifteen rating.
那么得到的SPF值为15
And if this process seems sketchy and full of issues…
这个过程是不是看上去很粗略而且有很多问题
Yes. Yes, it does.
没错 你说对了
For one, people turn red at different amounts of exposure.
首先 人的皮肤在不同程度的暴露下变红程度会有差别
So if you used a bunch of pale people in one study
因此如果用一组皮肤相对白的人做实验
and a bunch of people with darker skin in another,
再用一组皮肤较黑的人做实验
you’d get totally different results.
会得到完全不同的结果
Then there’s the amount of sunscreen used in these tests.
此外 这些测试中使用了大量的防晒霜
While there’s tons of variability between testers,
虽然测试者之间的差别很大
protocol calls for no less than two milligrams of
但实验方案要求每平方厘米皮肤上
sunscreen per square centimeter of skin
至少要有两毫克的防晒霜
and that’s significantly more than people tend to use in real life.
这比人们在现实生活中使用的要多得多
In one study, it was more than twice the amount.
在一项研究中 防晒霜的用量超过了日常的两倍
Ultimately,these tests just aren’t representative of what happens in the real world.
所以这些测试不能代表真实情况
They don’t take into account things like skin color,
他们没有考虑到肤色差异
or how much sunscreen people actually use.
或人们涂抹防晒霜的实际用量
So when you’re buying this stuff,
因此 在你买防晒霜的时候
it’s probably worth keeping those things in mind.
需要考虑一下以上因素
For example, maybe this means it’s worth putting on sunscreen more often than you currently do
例如 你可能需要更频繁地涂防晒霜
If nothing else, though,
别的不说
the good news is that researchers are at least aware that there’s a problem here,
好消息是研究人员至少意识到了存在的问题
and they’ve been working on protocols
并且一直在改进实验方案
to hopefully get more consistent results.
希望能得到更一致的结果
Their ideas include using robots that
其中包括使用机械设备
spread sunscreen evenly in all conditions
在各种情况下均匀涂抹防晒霜
and shifting towards standardized in vitro testing
在不使用人类皮肤的情况下
using chemicals in a dish no human skin involved.
用培养皿中的化学物质进行标准化的体外测试
This will let scientists get way more data points
这将使科学家获得更多的数据
and will improve accuracy.
并提高准确性
At the end of the day,
不管怎么说
SPF can be a helpful way to understand what you’re buying.
SPF可以帮助你了解你要买的防晒霜
To make an informed decision,
要选对防晒霜
you just need to know what it says
你只需要知道SPF是什么意思
and where those numbers are coming from.
以及这些数字来自哪里
And it’s also worth knowing
同样要知道的是
that not all hope is lost, either.
它并不是一无是处
Even if this is a bit of a flawed system,
即使这是一个有缺陷的方法
multiple studies have shown that consistent use of sunscreen,
但多项研究表明 持续使用防晒霜
even at low SPF,
甚至是低SPF值的防晒霜
reduces your risk of skin cancer.
也能降低患皮肤癌的风险
So,it’s always worth lathering up!
所以 防晒霜总是值得用的
If you’ve ever wished you just didn’t have to wear sunscreen
如果你曾希望自己不用涂防晒霜
Well,I’ve got some sad news for you.
那么 我有一些坏消息告诉你
Almost all amphibians, reptiles, birds,and fish
几乎所有的两栖动物 爬行动物 鸟类和鱼类
can make their own sunscreen.
都能分泌自己的“防晒霜”
Mammals are kind of the odd ones out.
哺乳动物是个例外
If you want to learn more,
如果你想知道更多
you can watch our episode about the missing sunscreen gene after this
可以看我们关于防晒基因消失的视频

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视频概述

防晒霜上标的SPF的意思

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收集自网络

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浩小浩

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视频来源

https://www.youtube.com/watch?v=5X2St42JD3w

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