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QUESTION

Often, while hiking, my companions and I treat the very early/late sun as being less harmful (as far as skin cancer and UV radiation are concerned). For example, we might not apply sunscreen immediately after waking, but only after an hour or so, or skip putting on another round of sunscreen if it's relatively late (say, an hour before sunset).

My question is- is the sun less dangerous at these times? Is this bad for us? We don't backpack/hike that often, so it's not a very common occurrence, and it hasn't led to sunburn as far as I know. But I would like to know if there is gradual damage being caused to my skin.

I asked this related question on the Fitness Stack Exchange, but it doesn't seem to be getting the attention (or answers) I'd like.

{ asked by Eyal }

ANSWER

Around sunrise and sunset, the sun is much less intense. You would get around 5 times less intensity in the first or last hour of sunlight than in the middle of the day. Here is a graph of this effect (It's from a paper, though the paper itself is behind a paywall), and another one which also shows the effect of latitude.

Therefore, while you can’t say that the sun at those times has no effect on the skin, it is much less dangerous than in the middle of the day. Do you put on sunscreen if you are outside for 10 minutes in the middle of the day? If not, then you’re getting about the same damage in 1 hour around sunset.

{ answered by Big General }
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