Ultraviolet Irradiation Can Sterilise, But It Can Also Bring About Skin Cancer. How?

The science behind it all tells us that the operating principles are the same. Should that be surprising to us or not?

Ultraviolet (UV) irradiation is something that most of us are familiar with in a superficial manner. We know that it exists, and we know that we can do certain things with it. But we don’t necessarily understand how it works, do we?

We know that when we’re out and about in the sun for too long, and we get exposed to too much UV rays from the sun, we’ll be at a higher risk of getting skin cancer, not to mention some uncomfortable degree of sunburn.

I was having a conversation with some of my students about UV sterilisation processes in a water treatment plant. We use UV rays to sterilise the treated water as one of the final steps in the process, which helps to weed out most unwanted micro-organisms/pathogens from the final water product.

How is it that one process can be beneficial to us, while the other can be so deadly? It’s not that clear cut now.

The answer lies in the science behind harnessing these UV rays

These UV rays are known to emit energy in the form of photon particles, and the energy that is emitted can be determined based on the work of the physicist Max Planck.

As these photons travel through space, they are able to be absorbed or emitted as a form of electromagnetic radiation.

That’s radiation physics in a nutshell.

What do these photons do, biochemically?

We do have to understand, then, that the structure of many proteins and the deoxyribonucleic acid (DNA) helices in a bacterial cell comprises multiple aromatic or heterocyclic rings with a ton of delocalised electrons floating around those rings.

The simplest aromatic ring that we know of is benzene:

Image source: Wikipedia

When UV light is projected onto these ring structures, the photons are able to provide sufficient energy to excite some of these delocalised electrons out of the stable ring structure.

It wouldn’t be that much of a problem if the excitation was reversible — if the excited electron jumps out of the stable ring structure and jumps back in without causing any lasting damage, then there wouldn’t be any lasting impact.

The problem is that the ring structure is stabilised enough on its own that a loss of a fringe electron doesn’t affect its stability — its core can withstand that loss.

However, this excited electron on its own is unstable — it needs to find some other electron in some other chemical structure that has is spinning in its opposite direction to couple with it for stability’s sake.

Meaning that it could actually attack some other stable structure, much like how a third wheel attempts to break up a stable marriage — and that would result in the propagation of reactive oxygen species (ROS).

Having these ROS around for the sterilisation of bacteria is a good thing.

The ROS would react with just about anything stable in the bacterial cells to propagate even more ROS.

Eventually, the cell’s DNA helix will also get affected by multiple unwanted chemical reactions with the ROS, and what would result at the end of the day would be a significant amount of DNA damage, which would force mutations of the cell’s DNA and prevent it from reproducing.

In that way, we can kill off unwanted pathogenic cells and sterilise the water. The sterilised water is then safe enough for us to drink.

However, in the same vein, the skin cells in our body also do contain these aromatic and heterocyclic rings.

When we expose ourselves to the sun’s UV irradiation for too long, this same photosensitisation process can occur, which results in DNA damage to our skin cells via the production of all those ROS.

All these ROS won’t cause skin cancer right away.

But we can see how these ROS can affect our skin structure, especially if they were to react with the collagen proteins that provide structural support for our skin.

When our skin loses its structural support, we’d see some areas of our skin start to collapse and lose their elasticity. Ridges and lines start to form. The dreaded W word that many people associate with aging — wrinkles, comes into play.

We’d also have cell mutations coming into play. If the autophagy process in one’s body is working sufficiently well enough, the mutated cells can be disposed of pretty efficiently such that it would not be likely for these mutated cells to accumulate into a critical mass.

Because if they were to accumulate into a mass — that’s the stuff that cancer tumours are made out of.

After all, do charred foods really cause cancer, or is it a problem of the immune system in removing and killing off all the defective cells that is the real issue?

Hence the marketing of paraben-free products for skincare health.

Because while parabens are useful preservatives, they do contain aromatic rings as part of their chemical structures.

And the UV rays from the sun are able to cause photosensitisation of the parabens. The aromatic rings in the aromatic benzoic acid rings on the parabens that we have slathered onto our skin as a form of protection from UV rays are themselves sensitive to UV irradiation, and are able to release electrons upon photosensitisation.

So if we aren’t careful enough, the skincare products that we do apply onto our skin for prevention against UV irradiation may be harmful to us upon UV irradiation.

And that can be damaging to us, especially if the autophagy mechanisms in our bodies aren’t functioning at tip-top condition!

Do feel free to check out Dr J’s various recommendations for paraben-free skincare:

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