One of the environmental disasters brought about by modern industrialization is the depletion of the ozone layer. This has spawned general responses such as the UV Index on the Weather Channel and an increase in the awareness of the hazards brought about by long-term exposure to the sun resulting in a proliferation of products offering a sun protection factor or SPF.
Dire warnings of the dangers to health have been issued by governments, scientists, and health care professionals. Increased incidences of cancer - particularly skin cancer - are a consequence of a decreased ozone concentration.
In 1995, a Nobel Prize in Chemistry was awarded to Paul Crutzen, Mario Molina, and F. Sherwood Rowland, for their work beginning in the early 1970s to unlock the mechanisms involved in ozone formation and depletion. Their work paved the way for international limits on substances which deplete the ozone layer, but a hole is still occurring over the Antarctic every year.
But what exactly is ozone depletion? How does it occur? And is there anything to be worried about in northern B.C.?
Ozone is a naturally occurring form of oxygen - an allotrope.
Several elements occur in multiple forms. The most famous is carbon with can be found as diamonds, graphite and buckyballs. All are pure carbon, but it in different structural forms.
The oxygen we breathe and use for respiration everyday consists of two oxygen atoms bonded together to form a diatomic oxygen molecule. Ozone is the combination of three oxygen atoms giving a slightly larger, and chemically distinct, triatomic molecule.
It is formed by the combination of a single oxygen atom with an oxygen molecule. This can occur in any number of ways - from a high energy electrical discharge in an arc welder or a lightning strike to the actions of sunlight on oxygen molecules.
In the upper atmosphere, the formation of ozone by sunlight is of fundamental importance to life on this planet. This is where the ozone layer occurs. It is a region in our atmosphere between 10 and 50 kilometres above the ground with a maximum concentration of ozone about 20 km up. At this altitude, there is enough oxygen to create ozone, but not too many other gases with which it reacts naturally.
The ozone in this region of the atmosphere is generated by the interaction of sunlight and oxygen molecules. High-energy light (light in the ultraviolet region of the spectrum) is capable of breaking the bonds between atoms.
Breaking an oxygen molecule apart yields single atoms which then combine with other oxygen molecules to give ozone.
The ozone molecules formed also absorb ultraviolet light, reacting to give back oxygen. Hence, the ozone layer of our atmosphere absorbs incoming UV light by continually making ozone molecules from oxygen molecules and destroying ozone to make oxygen.
The process is a delicate equilibrium which, unfortunately, can be upset by additional compounds.
Ozone depletion occurs as a result of the dispersal of chemical compounds into the atmosphere which react with the ozone causing it to break apart before it has absorbed any incoming light. Essentially, they bleed the equilibrium structure of the ozone layer. If enough ozone molecules are destroyed this way, then they do not absorb some of the incoming UV light and the amount getting to the surface of the earth increases.
This is a very unfortunate for those of us who live on the surface of this planet because just as the high-energy light can break apart oxygen molecules in the atmosphere, it can also break apart any compound with a bond. We (and all living things) are made up of countless compounds which, when exposed to UV light, break apart and give other compounds.
This breaking up of molecules by high-energy light can lead to everything from a tan to cancer to a compromised immune system.
UV light also affects plants and animals through much the same sorts of mechanisms.
It can even affect non-living systems. Simply put, changing the level of UV light reaching the surface of the Earth is bad for the ecosystem.
The good news is 30 years ago, the countries of the world were able to come together and commit to eliminating the compounds which exacerbate ozone depletion.
The Montreal Protocol was a major breakthrough in international cooperation on the environment. It took only 14 years to go from the science to an agreement.
The bad news is it will still take a very long time for our atmosphere to purge itself of the harmful compounds already in it. These are persistent and pervasive. Even with everything which has been done in the past 30 year and with the entire planet participating in the protocol, it is estimated ozone levels will not return to 1980 levels until 2050 at the earliest.
