Is there really a hole in the ozone layer?

Quite a few years ago whilst having a beer with my father in an Irish-themed Canberra pub and in discussion with a couple of former panel-beaters a statement was made that questioned the existence of a hole in the ozone layer. At the time I dismissed it as being a sort of weird fringe idea like faked moon landings or that full fat tasting skim milk exists.

It turns out that it’s not that fringe.

Now of course air in the Donald’s hypothetical apartment is exchanged with the outside atmosphere through heating and air conditioning systems, leaks and gaps in the building envelope and of course actual openings like doors and windows. Human beings and in fact all organisms that breathe oxygen (and even those that don’t) need to exchange gases with the atmosphere and cannot survive for long periods in sealed boxes. So the hypothetical hairspray will find its way out of the hypothetical apartment, even the good hairspray that lasts longer than 12 minutes.

I’m not going to explore in this post whether or not it is actually a good idea to use the atmosphere as an aerial sewer for all of the excess products and waste of our lifestyles, at least not today. What I do want to talk about here is how this whole ozone hole thing works when we can’t see it, what it has to do with hairspray and what it has to do with cancer. To address this, I’d first like to talk a bit about light.

You might be thinking “I know about light” and I’m sure you do. But bear with me, because light has some crazy properties that we need to talk about to get to the bottom of this story.

The light that we – two-legged walking sacks of water like you and me – use to see things in our daily lives isn’t the only thing that is shining in our faces, its just the stuff our eyes can detect. Our eyes are suited to a particular type of light that we call – sensibly enough – visible light. Our ears are kind of the same in that they can only hear certain frequencies of sound. This works fine for a musical instrument but isn’t so great for hearing the high pitch sound that a dog whistle makes (ultrasound), nor does it work for the low frequency vibrations created by a highway or a wind turbine (infrasound – oh look, more blog topic material!).

800px-dispersive_prism_illustration
White light is made up of all of the colours we can perceive. A cloudy moonless night sky is the opposite – total darkness.

The types of light that our eyes can detect form a part of a spectrum of light which is arranged by the wavelength of light. We don’t need to go into this though, all we need to know is that we see blue, green and red light and that each of those colours is but a thin slice of the electromagnetic spectrum as a whole.

 

Electromagnetic spectrum
Your TV can see some of these waves, the cells in your body may see others but the only ones we consciously observe as vision are the coloured ones that our eyes can see..In the coloured bar at the right you will notice that above the blue light is a thin strip of violet. Above violet is ultraviolet.

In the image, below the red end of the spectrum that we can see is an area that we call infra-red. Infra? Well that means below. Infra-red light is the energy given off by an object that relates to its temperature. We can detect infra-red light only by feeling it with our skin. We are very insensitive to it which is why we need to get very close to that kettle before we can tell if it has boiled recently or not. Our skin is sensitive to heat but not enough to detect a detailed image or at a distance. It is only as good as being able to tell shades of light from a very close distance. We are effectively blind to the infra-red world. Some snakes have a kind of vision (although it isn’t vision like we know it) that is able to detect heat to such a degree that it can use it to hunt. Of course this has been investigated by experiment, because no one has seen what a snake sees. Or have they?

Ever wondered how a TV receives the signal from the remote? A little LED in the remote control emits only infrared light and the TV only picks up infrared light. If you could see the infrared part of the electromagnetic spectrum you would see it flashing, but you don’t. Likewise you don’t see even longer wavelength radio waves, but your radio can pick them up.

Wasn’t this about the ozone hole?

Okay, so there are different kinds of light and with some fancy equipment we can detect when it is around when our eyes alone won’t do the job. Now on to ozone.

Ozone is an unstable molecule made of three oxygen atoms. The oxygen that we breathe has only two oxygen molecules (O2). One could say that ozone is therefore 50% better, but one would be oversimplifying greatly.

Oxygen_molecule
This is molecular oxygen, the type we breathe. It has two oxygen atoms that just love hanging out together.
800px-Ozone-CRC-MW-3D-vdW
This is ozone, with an extra oxygen atom hanging in there. This can’t last.

When it comes to how oxygen atoms hang out, two is a party and three is a crowd. The extra oxygen atom makes ozone very reactive. This is because whilst oxygen atoms are tight and happy just hanging together when there are only two, the extra oxygen atom can only ever hang on quite weakly and will always be the outsiders.

With enough oxygen and a spark you can even burn metal. Whilst not burning exactly, with a spare oxygen atom hanging on, ozone can react with things very quickly and without a spark. It is sometimes created artificially and used in a practical way to treat water as it reacts with germs and micro-organisms and – again simplistically – burns them into carbon dioxide and water. Ozone also has a smell, something oxygen doesn’t. If you’ve ever been around power tools or blending something up really well in the kitchen you have probably smelt ozone. It’s that electric motor smell. The ozone forms from oxygen in the air and is created in the little sparks that occur around some types of electric motor.

But, but, hairspray!

Chlorofluorocarbons – from here on CFCs – were regarded as wonder chemicals when they were first developed back in 1928. They are non-toxic, non-flammable and really good refrigerants. Previously ammonia had been used as a refrigerant in household appliances but had the nasty side-effect of killing the people in the house if it leaked. Because of their properties CFCs were used widely, including as hairspray propellant. In addition to working really well (apparently) hairspray with CFC propellant wouldn’t become a flamethrower in the hands of a teenager or arachnophobic householder.

 

CFCs are also really light which means they float really well. High in our atmosphere, a bit above where airliners fly (10km high) and for another 30 km higher there is a much higher concentration of ozone than normally occurs at ground level. This is called stratospheric ozone. Most of the ozone that is measured in the atmosphere on Earth is in this zone. This is known from using sensors to measure the presence and concentration of different gases in the atmosphere. There are a number of different methods for detecting ozone concentrations, including sensors similar to those that keep an engine with modern fuel injection running properly by detecting oxygen in the exhaust gas.

So we know we can detect ozone, we know that there is more ozone high up and we know that CFCs can float to where the ozone is.

Come back from the light

Lets flip back to the electromagnetic spectrum for a moment. You will be aware that certain materials are better at letting light through than others. Think coloured cellophane, which reflects some parts of visible light and lets others through. The image sensors in digital cameras – like the ones in a smartphone – are actually sensitive to the infra-red light we were discussing earlier. To prevent them from taking a photograph that displays things that you cannot see, filters are placed over the lens so that the infra-red light is blocked but visible light is allowed to pass.

220px-Active-Infrared-Night-Vision
In this image a video camera without an infrared light filter displays an image on the screen (there may be a source of infrared light in the room). To take the photograph of this scene, the camera that produced the above image would have to have been filtering infrared light.

Liquids and gases can also behave this way. Chlorine gas has a greenish appearance (chloros meaning green in ancient Greek and the reason for its name), because it reflects green light. Carbon dioxide absorbs infrared light whilst letting other pass, which is why it is a greenhouse gas.

It so happens that ozone in the atmosphere acts likes a filter for a particular slice of ultraviolet light-containing sunlight called UV-C. Parts of the UV spectrum called UV-A and some UV-B reach the surface of Earth and is what ruins plastic that has been left out in the sun too long. If UV light were visible light, UV-A would be red, UV-B would be green and UV-C would be in the blue-purple end. The higher in frequency (closer to the blue end) the light is, the higher in energy it is.

Whilst UV-A  can ruin your plastic bucket and can cause sunburn, UV-B and UV-C even more is a problem for just about everything that lives.

UV-C is very high energy. UV-C light is used in some water treatment systems to kill microorganisms. It is powerful stuff. This means it can destroy living cells. Skin cells of all kinds, plant and algae cells. It is this cell damage that can lead to skin cancer.

With an intact layer of ozone UV-C and parts of UV-B light is completely absorbed. The ozone (three oxygens) in the atmosphere is in fact created by this high energy UV light interacting with our normal, good-to-breathe oxygen (two atoms). This is a nice little trick for all of us down here on the surface as the protective shield of ozone, is continuously replenished by the very thing it is protecting us from.

The problem is when U.V. Light meets CFC McC Face.

UV light is powerful enough to cause cell damage in plants and animals, and powerful enough to crack 3 diatomic oxygen and make 2 ozone from its leftovers. It’s also powerful enough to knock the first C in CFC (Chlorofluorocarbon) right out of there, creating free chlorine gas.

Chlorine gas is like the twin sister to ozone and UV light. It is also highly reactive, it is also used to kill things, including likely in the water you drink from the tap. When two reactive chemicals inhabit the same space they tend to react with one another, and that’s what happens when chlorine gas and ozone get together. When this happens ozone is consumed more quickly than sunlight can replenish it and the layer of gas that protects Earth’s biosphere from the sun that also provides all their energy starts to disappear.

You might be thinking that surely there must be an upside to ozone depletion, right? Like if there is more incoming energy passing through the atmosphere, “does that mean my solar panels will produce more power when there is an ozone hole above me?”. Perhaps that is just me. The answer is no. Even though ultraviolet light is energetic, the part of the electromagnetic spectrum that the most common solar panels get derive the power from is roughly the same as the human eye. Some types are a bit more sensitive to infra-red red, others a little more to ultraviolet, but the contribution to their total power is many times less than visible light. There is no merit in an evil genius plan for growing the ozone hole and getting more power from solar power, at least using today’s commonly available solar panels. Anything else would be uneconomic and therefore whilst conceivably evil, would fail at the genius part.

I hope this has covered off what I led you to believe I was to talk about, that being how there could be a hole in the ozone layer and what it has to do with CFCs and cancer. This article outgrew its initial concept by a long way. For someone as ill-informed about hair styling as myself I have wondered a few times if it was worth continuing with. Nevertheless I will be back next week with a far shorter article seeking to answer technical questions that many never thought to ask. See you next time!

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One thought on “Is there really a hole in the ozone layer?

  1. KM Jan 14, 2017 / 9:33 pm

    1. How did you get so much information in your head in the minimal years you’ve had on earth?
    2. Are you related to Dr Karl?
    3. YOU SHOULD BE A SENIOR HIGH SCIENCE TEACHER or UNI TUTOR/PROF. If you had taught me science 17yrs ago instead of now, I might be really really useful to the world and not just scientifically curious and entertained by this blog. (The post-Trump world needs scientists who can inspire)
    4. I do not believe that you will be “back next week”. Your last post was….?over a year ago.
    5. Please do though

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