Remember all the hype around the hole in the Ozone? In the last 20 years there was a lot of talk around the depletion of ozone layer above the Antarctic. But the story doesn’t feature too often any more, and for a good reason. It’s recovering.
But what is ozone? Ozone is a gas similar to oxygen, which forms a protective layer in the stratosphere and absorbs most of the sun’s harmful UVB radiation. UVB radiation is one of the main culprits for skin cancer.
In the 1970s and 80s, it was discovered that the ozone layer was thinning. Chlorine in CFCs (chlorofluorocarbons) from fridges and aerosols, and chemicals emissions from the Concorde were reacting with the ozone, depleting it.
The main hole in the ozone was over Antarctica. But why was that a problem? Because it didn’t just include the South Pole, it affected a large part of Australia and New Zealand, resulting in a skin cancer incidence four times higher than the global average.
The Skin Cancer Foundation has a nice graph mapping the depletion of the layer since 1970. Deep red colour (500 Dobson units) marks areas where the layer was thick, and blue (100 Dobson units) marks the recent thin parts, directly over the South Pole.
Image Source: Skin Cancer Foundation
Why does the hole happen over Antarctica? The answer lies in some fairly strange stratospheric weather conditions. Special types of cloud called polar stratospheric clouds form in the extremely cold night time air (- 42 degrees C) and cause chlorine molecules to break apart, forming free radicals. When the sun rises the UV light helps catalyse the destruction of the ozone by the chlorine free radicals.
Plus there is the ‘polar vortex.’ This is a circular wind pattern that stops ozone from other areas from filling the gap, perpetuating the hole. There is also a polar vortex over the Arctic – it is responsible for some of the wild weather in North America at the moment.
So what has happened to the Ozone layer recently? Its not in the news as much these days, mainly because its healing, and good stories aren’t often as newsworthy.
After an international ban on CFCs levels are finally declining and a recent news article by Huff Post reported that the hole in the ozone will recover completely by 2070.
What might have happened if we had done nothing about CFCs? By 2060 Ozone levels would have dropped by two thirds. Less ozone would mean more UVB rays reaching our skin, and a faster rate of burning – up to three times faster.
However, although UVB rays were thought to be the primary culprit in the development of skin cancer, we now know that UVA can also have a role. Both types of UV rays penetrate the skin and cause damage to the DNA. Most of the time DNA damage does little more than speed up aging, but if it happens in a critical place, skin cancer can develop. And its not just moles you have to watch out for, skin cancer can happen anywhere on the body. Any change should be watched carefully by a doctor and through self monitoring techniques such as mole-mapping.
It looks like we have avoided a major epidemic, but that’s not to say its safe in the sun. Now we know that UVA light causes a lot of damage, and the ozone doesn’t protect us from that.