On beaches as well as on the cricket ground, it is always possible to spot people with some kind of cream on their bodies or faces. Remember the South African pace bowler Alan Donald or ‘White Lightning’ as he is called, with “war-paint” on his face? No, it is not an attempt at camouflage, simply an effort to gain protection from the ultraviolet rays of the sun.
And therein lies a paradox – it is the light and heat of the sun that sustains life on earth, but among its many friendly rays are some harmful ones as well. These ultraviolet (UV, as they are called in all popular sunscreen lotions) rays can kill life forms, including humans, if they are exposed to it beyond a limit.
Ultraviolet: Is it a shade of violet?
The white sunlight that we see, is formed of seven different colours, or the VIBGYOR – short for violet, indigo, blue, green, yellow, orange, red. Violet is at one end, while red is at the other extreme of this visible band of light.
Only that light which falls between these colours, is visible to humans. Light rays which fall below the violet colour, are called ultraviolet rays. Those that fall beyond the colour red are called infrared. Sunlight contains both ultraviolet and infrared rays.
How are we protected from these rays?
These rays have always been a part of sunlight, but they have become big threats to humans today. Why? The earth’s atmosphere is composed of several layers. We live in the Troposphere where most of the weather patterns such as rain, snow and clouds, occur. Above the troposphere is the Stratosphere.
Supersonic jet airliners such as the Concorde fly in this layer, whereas subsonic commercial airliners usually fly in the troposphere. It is in the stratosphere that the ultraviolet rays strike the oxygen, converting it into a gas called ozone.
Friendly ozone layer
The ozone in the stratosphere absorbs most of the harmful ultraviolet rays from the sun. These rays can otherwise cause skin cancer and damage vegetation, among other things. Exposure to these ultraviolet rays kills bacterias and several microorganisms that are very important for the earth’s ecology. Unfortunately, this layer is getting depleted.
The ozone layer has a hole in it
In 1996 studies conducted by US National Aeronautics and Space Administration (NASA) revealed a big hole of roughly 10 million square miles (greater than the total surface area of North America) over the continent of Antarctica. This is known as the ozone hole. As a result of this large amount of ultraviolet rays enter the lower atmosphere. If not checked in time the ozone depletion can cause dangerous consequences.
Human hand in ozone depletion
Quite interestingly the destruction of ozone is a human phenomenon. Like air pollution, reducing the levels of pollutants that we emit in the atmosphere, can control it. Most air-conditioners, refrigerators and spray cans contain a substance called CFC (chlorofluorocarbons) that destroys the ozone gas, converting it into other gases. This is what has caused the ozone hole over a period of time.
It is precisely for this reason that worldwide standards for air-conditioning equipments are being modified. A new substance called HFC (hydrofluorocarbons) is being used instead of CFC.
So, the next time you use that room freshener or your perfume spray, think of the ozone hole that could be expanding with every passing second.