And fair, we don’t.
But a couple of things we do know that weren’t covered - egregiously so - is that aging is UV damage. Sometimes called photoaging, wrinkles, sun spots, discoloration, fine lines, grey hair, all of that shit that you associate with someone visibly looking old is sun damage.
So the picture that the article paints of some pasty nerds in offices shielding themselves from all UV and thus: they might as well be smoking… it doesn’t even touch on why people might be doing this.
Both kurgezadt and veritasium did some really great videos on photoaging and it’s worth checking out if this is new information to you.
Do you have any sources for that?
> Sun radiation affects hair properties as color, luster, mechanical resistance, the content of proteins and others.
TLDR Yes it impacts color. Further reading can be found in the 75 studies that can be found in the references section.
In contrast (based on my own unscientific observations!) greying typically begins in small areas, and often on the temples - not what I'd expect if caused by UV damage.
This is distinct from UV bleaching of the pigments in the hair.
The actual rule is derived from your location’s safe UV index zones, which is found out by determining what local time the UV Index <= 2. Above 2, wear some amount of protection.
It's been completely grey, overcast, and raining here all day and the UV index sat between 3 and 5.
I find that being exposed to the value (e.g. 4) while being able to see the suns effect (e.g. cloudy) gives me a better feel for conditions.
(you can also wear clothes to block sun instead of sunscreen so you don't necessarily need sunscreen at all)