How can you know?
Yes people have been sitting in the sun for thousands of years, and I would say many died from skin cancer, but then we did not know about the harm the sun could do then - did we?
Is there a time/type of exposure - I do not think so - I think that depends on our skins and how strong the suns rays are on any given days..so I cannot see how you can say you are 100% certain - or why you would want to.
Poppy
It does depend on our skin, it also depends on the chemicals and antibiotics we consume which lower our resistance to the UV light thus increasing our chances of skin cancer. Exposure to sun light is not the main cause of skin cancer, skin type, hereditry features and chemicals most likely are. The three things above are what increases the likelihood of us being at risk from the sun as oppose to us just being at risk from the sun if that makes sense.
It's like saying pollen is harmful because some people get hayfever.
I've seen a documentary on this. They tested Linda Lusardi's skin for damaged cells and susceptibility to skin cancer given she has used a sunbed maybe 3 weeks+ a week for around 30 yrs against someone who has never been on a sunbed and NEVER sat out in the sun.
Result?
The one who'd never sat out in the sun had skin cell damage and was at HIGH risk of skin cancer. Linda however was fine.
Likely reason, candidate B was naturally fair.
I also read another piece of research that said the sun offers protection from skin cancer. But of course it all depends how you are in the sun, your skin type and those chemicals.
It's a case of reading up on it.
I am not a Dr and this should not be taken as medical advice. It is based on my own reading and that documentary etc. I suggest anyone with concerns does their own reading and research. Meanwhile I am confident Poppy I won't get skin cancer (due to the sun) for these reasons:
I am not naturally fair
I have never burned in the sun
I don't sit in sun that would burn me for a period long enough to burn me
I have never been a big sun worshipper so didn't damage my skin from 'over exposure' as a child or other
I do not consume or are exposed to the chemicals that lower my protection from UV light.
I am and have always been sensible in the sun and tan naturally and safely.