The global efforts to phase-out the various forms of Ozone Depleting Substances (ODS) is succeeding. as the 196 countries that were the signatories to the Montreal Protocol on Substances that Deplete the Ozone Layer signed on September 16, 1987, implemented their respective initiatives to stop the production and consumption of ODS on agreed schedule, to contain the further damage to the ozone layer.

Shri Jairam Ramesh, Minister of State for Environment and Forest of India said that the Montreal Protocol has been hailed as one of the most successful examples of an international treaty. Shri Ramesh informed that "over 97% of controlled Ozone Depleting Substances have been phased out by the Montreal Protocol. The end of 2009will mark another significant milestone in the history of its implementation, with the use of potent ODSs-CFCs, Carbon TetraChloride (CTC) and Halons, except pharmaceutical grade CFCs used in the manufacture of Metered Dose Inhalers-being ceased completely.

The Ozone layer id a concentration of ozone molecules in the stratospher, about 10 to 50 kilometers above the Earth's surface. About 90% of the planet's ozone is in the troposphere, the region closest to Earth. Ozone found on the Earth's surface is formed from pollutants, and is considered "bad ozone," because it is harmful to humans, plants and animal life. The stratospher ozone is a thin fragile shield that envelopes the entire Earth, which efficiently filters and screens almost all of the harmful ultraviolet rays, particularly, it blocks off 90% of the harmful Ultra-Violet-B, and 100% of Ultra-Violet-C, while allowing most of the neneficial Ultra-Violet-A to reach the Earth's surface. Beneficial ultra violet radiation from the sun is the primary sunlight used by plants to manufacture food and nutrients, and utilized by the animal species as its principal sources of energy.

Ozone molecules have relatively low abundance. For every ten million air molecules, there are only three ozone molecules. Ozone molecules are dispersed in the atmosphere, and therefore, the physical thickness of the ozone layer is tens of kilometers. However, if all ozone molecules are brought together and uniformly distributed into a gas layer over the globe, the resulting layer of pure ozone would have a thickness of only three to five millimeters.

What are the consequences of over exposure to the sun's harmful radiation?

According to a report from the National Oceanic and Atmospheric Administration's Surface Radiation Research, too much exposure to UV-B harms not just humans but other living things as well. On land UV-B radiation endangers all life forms. The immune systems of humans exposed to high level of UV-B will deteriorate. Hence, they will become more prone to diseases and other disabilities such as skin cancer, eye cataract and blindness. Physically, they will age more rapidly. Further, their sources of food will become more limited since UV-B inhibits the growth of crops and trees.

On water, UV-B radiation penetrates the ocean floor damaging the propagation of phytoplankton organisms, the primary food source of most marine life. This affects the marine food chain which also involved humans at the end of the food chain. Many marine species are humans' main sources of food. Fish ggs and young plants with developing leaves are also particularly susceptible to damage from exposure to UV.

What's happening to the ozone layer?

Due to reactions to Ozone Depleting Substances, the ozone layer is thinning and creating a hole in the sky or ozone hole allowing the entry of greater concentrations of UV-B, and putting all life forms at risk.

The ozone hole was first observed in the Antartic area in the early 1980's. As of September 2005, the size of the ozone hole is about 22 million square kilometers which is almost as big as the United States and Canada combined.