When we choose a sunscreen, we can compare application method, the SPF, and the active ingredients.
当我们选择防晒品时可以比较一下使用方法，SPF值，和活性成分。
Sprays can be convenient to put on, especially when you're wet,
喷雾使用起来比较方便，尤其是当你身上湿了时候，
but a recent study found that most people don't apply a thick enough layer to get full protection.
但最近的一项研究发现，大多数人没有喷到足够厚以得到充分的保护。
And the possible health risks of inhaling sunscreen compounds from a spray cloud
而且吸入防晒化合物可能带来的健康风险
might make you consider reaching for that bottle of lotion instead.
也许会让你考虑用一瓶霜来代替。
Opt for a sunscreen with an SPF of at least 15, although 30 is better.
选择具有至少15的SPF防晒剂，虽然30更好。
SPF is a nonlinear scale of how much UVB radiation is needed to give protected skin a sunburn.
SPF是指需要多少非线性标度给皮肤保护以防被UVB照射晒伤。
SPF 15 does a pretty good job by blocking 93% of UVB rays.
SPF15通过阻断93％的UVB射线起到了很好的作用。
You get a slight increase as SPF goes up, with SPF 30 blocking 97%, and 50 blocking 98%.
随着SPF上升略有提高，SPF30可以阻挡97％，50可以阻断98％。
SPF is based on the quantity of solar exposure.
SPF是基于太阳能曝光量来定的。
So how much time you have before you start to burn really depends on a long list of factors,
所以，你在晒伤之前有多少时间，实际上取决于一长串的因素，
including your genetics, and when, where, and how you spend your time in the sun.
包括你的遗传，何时，何地以及你在阳光下干什么。
Even though US marketed sunscreens have been deemed safe by the FDA,
尽管美国市场上销售的防晒霜已被FDA认定为安全，
scientists are still researching the effects of many active ingredients on the human body.
科学家们仍在研究多种活性成分对人体的影响。
So if you're worried about potential irritants, look for mineral-based formulas with zinc oxide or titanium dioxide.
所以，如果你担心潜在的刺激，那就找找含有氧化锌或二氧化钛的矿物质公式。
Even though they may go on a bit thick at first, they're less irritating than carbon-based chemical sunscreens.
尽管开始的时候可能会厚一点，但是他们比碳基化学防晒剂的刺激性较小。
These mineral-based sunscreens are preferential for the environment, too.
这些矿基物防晒霜对环境也更好。
