过度暴露于紫外线（UV）辐射下，如阳光，晒黑机，或日光灯。
Overexposure to ultraviolet ( UV) radiation, such as from sunlight, tanning booths, or sunlamps.
阳光能够刺激黑色素细胞产生黑素，这是因为黑素要在紫外线的辐射下保护我们的身体。
Sunlight is therefore a stimulus for melanocytes to produce melanin because they are trying to protect the body from UV rays.
阳光下活动减少意味着暴露于紫外线辐射的时间缩短，而紫外线辐射会生成自由基，对机体造成损害并加速组织衰老。
Reducing the time spent in sunlight helps minimise exposure to UV radiation, which creates free radicals known to damage and age tissues prematurely.
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