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修復蛋白的水平天然地在早晨上升，晚上下降，早晨暴露在紫外線下是最安全的。

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.

早起的鳥兒有蟲吃—還不會得皮膚癌。因為一項新的老鼠研究顯示，對于人類，早晨做日光浴對DNA造成永久性傷害并引發皮膚癌的可能性更低。

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修復蛋白XPA的水平和我們不同—它們在早晨達到峰值，夜里則從低谷回升（譯注：與后文互相矛盾，原文這里應該搞反了，應為：夜里到峰值，而早晨到最低值。參考原文后面的評論）。研究人員將兩組老鼠在不同時段，當XPA達到最低水平，凌晨4點左右，和當XPA達到最高水品，下午4點左右，置于相同的紫外線照射下。

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]

被紫外線照射的老鼠，DNA修復蛋白水平低的一組其皮膚癌的發展速度更快，5倍于晚間接受“紫外線浴”的同伴。此研究發表于《美國國家科學院院刊》(Proceedings of the National Academy of Sciences).[Shobhan Gaddameedhi等，生理周期對皮膚癌的抑制作用]

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.

與老鼠不同，人類不在夜間活動（譯注：誤XD），所以我們的XPA水平升高和降低的時段也不同。對人來說，XPA的DNA修復水平在早晨最好，因此早晨看起來是日光浴的最安全時段。所以，如果你不想得皮膚癌，去日光浴沙龍的話就得趕早—最好不要去。