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Depletion of ozone layer
Highlights
A threat to bio-diversity September 16 was designated by the United Nations General Assembly as the International Day for the Preservation of the...
A threat to bio-diversity
September 16 was designated by the United Nations General Assembly as the International Day for the Preservation of the Ozone Layer. This designation was made on December 19, 1994, in commemoration of the date, in 1987, on which nations signed the Montreal Protocol on substances that deplete the ozone layer. Cooperation between people, centre and state governments, is the dire need of the hour to phase-out the ozone depleting substances (ODSs) in the country
JA PHILIP RAJ
Of all the gases present in the atmosphere, ozone is the most dangerous and highly toxic in nature. If ultra violet rays fall on earth, life would be impossible. Ozone acts as shield not to allow UV rays to fall on earth. Thus it is responsible for proper functioning of bio-diversity. Ozone (O3) gas is made up of atoms of oxygen. It is mostly concentrated in the stratosphere which is around 22km above the earth. It is blue in colour with a pungent smell and is highly toxic.
AGENTS RESPONSIBLE FOR DEPLETION OF OZONE
The UV rays have a wave length shorter than visible light which ranges between 0.4u to 1nm. Brief exposure of UV rays causes sun burn and long term exposure causes skin cancer. In 1970’s, during a survey at the Antarctic, scientists found that the amount of ozone layer had decreased significantly which formed a hole in the Antarctic which later was also found in the Arctic. The agents responsible for depletion of ozone are group of chemicals called Chloro fluoro carbons (CFCs) which are commonly used in refrigerators, aerosol sprays, cleaning solvents and packing material like polystyrene
PROCESS OF REACTION
When CFCs react with sun light in upper atmosphere, a gas called chlorine monoxide is produced. This gas is highly reactive and acts as catalyst for the ozone break down. In 1985, forty countries signed a protocol in Montreal UN convention to phase out the use of CFCs by the end of 20th century. The European Union proposed a total ban on the use of CFCs by the end of 1990. A satellite of NASA measured and monitored the variation in ozone at high altitudes to get a clear picture. But the CFCs have a long life and can remain for more than 80 years. So damage to ozone layer may last for a long time.
ADVERSE EFFECTS OF UV RAYS
If earth is exposed to UV rays, we will be affected by skin cancer, cataract and reduction of effectiveness in human immune system. Besides, it also affects phytoplankton in oceans interfering with photo synthesis of plants effecting marine ecosystem. Air borne solid and liquid particles emitted by various industrial processes such as blasting, drilling, grinding and dying, causes severe lung diseases. Although ozone is a toxic gas, it is considered relatively safe if its quantity is lower than thirty parts-per notation (PPB). Prolonged exposure to UV rays results in acute and chronic health effects.
Sunburn and sun tan are prevalent among them. Long term radiation induces acute degenerative changes in cells, fibrous tissues and blood vessels which leads to premature skin ageing. It also causes an inflammatory reaction of the eye called photokeratitis Skin cancer and cataract affects nearly 2-3 million people with non-melanoma skin cancer and 1,32,000 people with melanoma skin cancer every year worldwide. Non melanoma skin cancer can be removed through surgery where as malignant melanoma contributes more to death rates. Nearly 12-15 thousand people turn blind because of cataract every year. Nitrous oxides in the presence of sunlight reacts with hydrocarbons to produce highly poisonous gas responsible for asthama. Besides it also causes bronchitis and broncho–pneumonia.
ACTIONS TO AVOID DEPLETION OF OZONE
The action to avoid depletion of ozone was taken up in 1975. In 1978, US banned non-essential uses of CFCs as propellants in some aerosols such as hairsprays, deodorants, antiperspirants which was followed by Swedon, Norway and Canada. In 1990, Clean Air Act amendments, including title VI for stratospheric ozone protection was signed into a law. In 1994 and 1996, US discharged production of import of halons and CFCs like carbon tetra chloride, trichloroethane and hydrobromofluoro-carbons respectively. The developing countries of Montreal Protocol, freezed the production of methyl bromide in 2002.
VARIATION IN THE UV LEVELS
The higher the sun is in the sky, the higher are the UV radiation levels. The radiation level varies with time of the day and time of the year. The highest level occurs around midday during summer. Places closer to the equator receive higher radiation levels. Under the cloudless skies, the UV levels are at its peak. At higher altitudes, the UV radiation will be less. With every thousand meters, the levels of UV radiation increases by 10-12% .
ADVANTAGEOUS EFFECTS OF UV RAYS
Small amounts of UV radiation have positive outcomes too. It helps in production of Vitamin D and is used to treat diseases like rickets, psoriasis and eczema. According to WH, 20% of blindness is due to exposure to sun, particularly in India and Pakistan. In recent years, the rate of skin cancer had increased due to outdoor sunbathing. Unfortunately children, adolescents and adults perceive sun tan as a symbol of attractiveness. UV radiation not only damages human health, but also effects plants and animals. Besides it affects rubber, nylon, plastic, dyes and paints. Lower level ozone causes acid rain.
ULTRA VIOLET INDEX
Many countries in the world promote sun protection and large percent of people are aware of ultra violet index but don’t understand its meaning. Sun protection programmes are urgently needed to make the people aware of the health hazards of UV radiation so as to achieve changes in life style and protection of flora and fauna on earth.
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