What's The Difference Between Ultraviolet Irradiation For Sterilisation And Skin Cancer?

The science behind it all is exactly the same, which can be quite surprising… or is it?

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?

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

Therefore, as we are aware, UV irradiation can kill.

An exposure to excessive UV irradiation from the sun’s rays when we’re out in the sun can also increase the risk of developing skin cancer.

But how is it that one process can be beneficial to us, while the other can be so deadly?

That’s what they couldn’t wrap their heads around.

The answer lies in the science behind harnessing these UV rays

These UV rays are known 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:

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.

Now, it wouldn’t be that much of a problem if the excited electron jumps out of the stable ring structure and jumps back in.

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 pretty 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 the ROS, and what would result at the end of the day would be a ton of DNA damage, which would force mutations of the cell’s DNA and prevent it from reproducing.

So we’ve killed off the bacterial cells. Good enough.

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.

Of course, these ROS won’t cause skin cancer right away.

But we can see how these ROS can affect our skin structure… because what 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 its 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 one’s autophagy is working sufficiently well enough, the mutated cells can be disposed of pretty efficiently such that an accumulation of the damaged cells can be reduced.

However, if one’s autophagy isn’t working sufficiently well enough… these mutated cells may end up growing and multiplying to a point where they cannot be disposed of as efficiently as they ought to be…

And that can result in the development of a cancerous tumour.

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 here?

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 our autophagy mechanisms aren’t in tip top condition!

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

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