Freones

In out lives we use substances called freoens. What are freons?
Freons are colorless liquids or gases. They were used as coolants or pressurizers in spray can products, including drugs. In the 1970s, scientists discovered that these chemicals were destroying the earth's ozone layer.
Freons are gases at normal room temperature, liquids when cooled or compressed. Spilled liquid freons do not remain at the spill state for more than a few minutes before they evaporate. If liquid freons leak into soil before evaporation, it can seep into groundwater.

Freons are chluorofluorocarbons (CFCs) as CCl3F, CCl2F2 or CCl2F-CClF2 and we use them because of their useful properties:
They are very stable and sometimes non-flammable
They have very low toxicity
They are odourless (withou anu smell)
They are volatile, with a wide range of boiling points.

A lot of them we use in our fridges, other as insecticide, paint, or hair lacquer. These areb things withouth which we can't imagine our lives.
But we have to consider also that freons also damage our earth. They destroy ozone layer. Ozone Layer is a region of the atmosphere from 19 to 48 km above the earth's surface. It is very important for our living. People don't realize that but we can't live without ozone layer. It's because it prevent ultra-violet radiation to penetrate onto a earth's surface. If there wasn't ozone layer, we would all have cancer of skin and that's the reason why we have to try to decrease the usage of freones.

The twentieth century
Has witnessed an important scientific and technological development, especially in the industrial countries. This was accompanied by a scientific interest in the contemporary environmental problems, with the depletion of the Ozone layer and what is known as the “Ozone Hole” taking the leading place among the international environmental concerns, over which a lot has been said during the past twenty years.


Given the fact that the problem is an international one, it was necessary to have a worldwide co-operation and to intensify efforts in order to limit the activities that emit ozone-depletion gases. Efforts were also exerted to reduce or forbid the use of such substances in order to stop the negative effects that have been accumulating during the past years creating this dangerous hole.

In the early 1980s
Research scientists working in Antarctica have detected a periodic loss of ozone in the atmosphere high above that continent. The so-called ozone “hole,” a thinned region of the ozone layer, develops in the Antarctic spring and continues for several months before thickening again. Studies conducted with high-altitude balloons and weather satellites indicated that the overall percentage of ozone in the Antarctic ozone layer is actually declining. Flights over the Arctic regions found a similar problem developing there.

In 1987 the Montréal Protocol
A treaty for the protection of the ozone layer, was signed and later ratified by 36 nations, including the United States. A total ban on the use of CFCs during the 1990s was proposed by the European Community. In December 1995 over 100 nations agreed to phase out developed countries' production of the pesticide methyl bromide, predicted to cause about 15 percent of ozone depletion by the year 2000. Production of CFCs in developed countries ceased at the end of 1995 and will be phased out in developing countries by 2010. Hydrochlorofluorocarbons, or HCFCs, which cause less damage to the ozone layer than CFCs do, are being used as substitutes for CFCs, until 2020 in developed countries and until 2016 in developing countries. To monitor ozone depletion on a global level, in 1991 the National Aeronautics and Space Administration (NASA) launched the 7-ton Upper Atmosphere Research Satellite. Orbiting earth at an altitude of 600 km, the spacecraft measures ozone variations at different altitudes and is providing the first complete picture of upper atmosphere chemistry.

The World Meteorological Organization
Observed a 45 percent depletion of the ozone layer over one-third of the northern hemisphere, from Greenland to western Siberia, for several days during the winter of 1995-1996. The deficiency was believed to have been caused by chlorine and bromine compounds combined with polar stratospheric clouds formed under unusually low temperatures.


How is the ozone layer destroyed?
Freones are released into the atmosphere, they rise and are broken down by sunlight, whereupon the chlorine reacts with them and destroys ozone molecules—up to 100,000 per CFC molecule. The ozone destruction mechanism involves a catalytic chain reaction, so that a single free chlorine atom can destroy several hundred ozone molecules, so it doesn't take as much atomic chlorine as you might expect.
For this reason, the use of CFCs in aerosols has been banned in the United States and elsewhere. Other chemicals, such as bromine halocarbons, as well as nitrous oxides from fertilizers, may also attack the ozone layer. Destruction of the ozone layer is predicted to cause increases in skin cancer and cataracts, damage to certain crops and to plankton, and an increase in carbon dioxide due to the decrease in plants and plankton.

What could ultra-violent radiation do?

How does the ultraviolet radiation affect human skin?
One of the most obvious and clear effects of the ultraviolet radiation (UV-B) is sunburn, known scientifically as erythema. This radiation could damage the genetic material in skin cells resulting in cancerous diseases.

How does the ultraviolet radiation affect the eye?
Being exposed to the ultraviolet radiation could lead to Eye Cataracts in the human eyes, acute and painful inflammation of the cornea. A chronic exposure to the radiation could damage the eye.

What are the effects on plants?
A lot of plants are sensitive to the ultraviolet radiation and experiments have shown that the exposure of certain agricultural crops such as rice or soy beans to the ultraviolet radiation results in smaller plants and lower yields. It could also alter crop plants chemically, potentially reducing nutritional value.

What are the effects on the marine and aquatic life?
Experiments have shown that the increasing ultraviolet radiation harms phytoplankton, zooplankton, juvenile fish and larval crabs and shrimps. Harming these small organisms could threaten the productivity of fisheries.

Conclusion
When we know all these things about freons and ozone layer we think that people really should reduse the using of them. They damage ozone layer which protect us against ultra-violet radiation. This ultra-violet radioation damage our health and also the nature. Su we should really think about it and start using another substances, like hydrochlorofluorocarbons. This would help to save the Earth.