Why does sunlight cause cancer?

Cancer is when cells with damaged DNA grow. Thus, for example, skin cells, but with broken DNA, so that they are not normal skin cells and, for example, can no longer perform the functions of normal skin cells. Or just grow too fast, so there are thick lumps that make the problems.

Such DNA damage happens all the more often, the more often the DNA is copied to allow new cells to grow by cell division. Simply because there is a risk of errors during each copying process.

So, now, skin cells are among the few cell types in the body that constantly grow up to the end of life. In the lowermost skin layer cells divide and from each cell division a cell migrates to the outside, becomes part of a new skin layer, while the return cell becomes ready for the next cell division. On the outside of our skin there are some layers of skin cells that have long since been destroyed and, so to speak, only offer protection with their shells. If they drop, we call the shed.

But because skin cells are so often reproducible, there is already an increased risk that there will eventually be errors in DNA replication and cancer.

So, now everyone knows that light consists of rays. Sunlight is a colourful mixture of different rays, for example those we can see as colors (if they are no longer mixed), but also infrared rays (heat radiation) and UV radiation with a particularly short wavelength.

Some of them can penetrate the skin and destroy skin cells. You know as a sunburn. This means that skin cells now have to grow out of schedule – if this happens frequently, that means that the skin cells have to reproduce much more frequently than was actually planned by nature, so there is also a greater risk of DNA copying errors.

And again a part of the UV rays can penetrate so deeply into the skin that the DNA of those skin cells which multiply by cell division is damaged. There are repair mechanisms for DNA damage and normally cells also have a kind of self-destruction program if they have irreparable DNA damage. But these fuses aren’t perfect, and it’s possible that even skin cells can’t repair their DNA and don’t destroy themselves… and continue to reproduce. Then you have an ever-increasing pile of skin cells with DNA damage. And that’s skin cancer.

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In lung cancer, this is quite similar, except that there are no rays, but the poisons from cigarette smoke.