Levels of a DNA repair protein naturally rise in the morning and fall later in the day, which may make exposure to UV safest early.

DNA修复蛋白的水平天然地在早晨上升，晚上下降，早晨暴露在紫外线下是最安全的。

The early bird gets the worm—and may avoid skincancer. Because a new mouse study suggests that, for humans, tanning in the mornings may be less likely to permanently damage DNA and cause skin cancer.

早起的鸟儿有虫吃—还不会得皮肤癌。因为一项新的老鼠研究显示，对于人类，早晨做日光浴对DNA造成永久性伤害并引发皮肤癌的可能性更低。

A mouse’s levels of the DNA-repairing protein XPA are different from ours—they peak in the morning and bottom out in the evening. Researchers exposed mice to UV radiation when their XPA was at its minimum level, around 4 a.m., and others to the same rays around 4 p.m., when XPA levels peaked.

老鼠的DNA修复蛋白XPA的水平和我们不同—它们在早晨达到峰值，夜里则从低谷回升（译注：与后文互相矛盾，原文这里应该搞反了，应为：夜里到峰值，而早晨到最低值。参考原文后面的评论）。研究人员将两组老鼠在不同时段，当XPA达到最低水平，凌晨4点左右，和当XPA达到最高水品，下午4点左右，置于相同的紫外线照射下。

Mice who tanned while low on the repair protein developed skin cancer faster and five times more frequently than their evening-tanning counterparts. The study is in the Proceedings of the National Academy of Sciences. [Shobhan Gaddameedhi et al, Control of skin cancer by the circadian rhythm]

被紫外线照射的老鼠，DNA修复蛋白水平低的一组其皮肤癌的发展速度更快，5倍于晚间接受“紫外线浴”的同伴。此研究发表于《美国国家科学院院刊》(Proceedings of the National Academy of Sciences).[Shobhan Gaddameedhi等，生理周期对皮肤癌的抑制作用]

Unlike mice, humans are not nocturnal, so their XPA levels rise and fall at different times. In people, XPA is at prime DNA-repairing levels in the morning, which thus looks the safest time for UV exposure. So if you want to avoid skin cancer, probably go to the tanning salon early—or better yet, don’t go at all.

与老鼠不同，人类不在夜间活动（译注：误XD），所以我们的XPA水平升高和降低的时段也不同。对人来说，XPA的DNA修复水平在早晨最好，因此早晨看起来是日光浴的最安全时段。所以，如果你不想得皮肤癌，去日光浴沙龙的话就得赶早—最好不要去。