The ozone layer is a thin layer of gases that surrounds the earth. It acts as a sunscreen for the earth, blocking out most of the sun's UV radiation. Over the last few years, the ozone layer has become slightly thinner, allowing more damaging UV rays to reach the earth's surface than before.

The best strategy for ozone protection is to avoid purchasing products containing ozone-depleting substances. Ask before you purchase fire extinguishers, foam products, refrigerators and air conditioners. Refuse to purchase products containing ozone-depleting substances if alternatives are available. Write companies still using these chemicals and voice your concerns.

Ozone is very rare in our atmosphere, averaging about three molecules of ozone for every 10 million air molecules. In spite of this small amount, ozone plays vital roles in the atmosphere. This document provides answers to some of the questions that are most frequently asked about ozone and the changes that have been occurring in recent years.

Contrary to what a lot of people think, none! 'Good' and 'bad' ozone exist (like good and bad cholesterol) but neither plays any part in global warming. The 'good' ozone is to be found 15 km above our heads in the famous ozone layer. This layer is permanent and protects us from harmful ultra violet rays emanating from the sun. The hole in the ozone is produced by chlorofluorocarbons (CFC), chloride gases which up until 1987 were used in aerosol cans and refrigerating systems.

Ozone's unique physical properties allow the ozone layer to act as our planet's sunscreen, providing an invisible filter to help protect all life forms from the sun's damaging ultraviolet (UV) rays. Most incoming UV radiation is absorbed by ozone and prevented from reaching the Earth's surface. Without the protective effect of ozone, life on Earth would not have evolved the way it has.

Global ozone levels declined an average of about 3 per cent between 1979 and 1991. This rate of decline is about three times faster than that recorded in the 1970's. In addition to Antarctica, ozone depletion now affects almost all of North America, Europe, Russia, Australia, New Zealand, and a sizable part of South America. Short term losses of ozone can be much greater than the long term average. In Canada, ozone depletion is usually greatest in the late winter and early spring.

The depletion of the ozone layer leads, on the average, to an increase in ground-level ultraviolet radiation, because ozone is an effective absorber of ultraviolet radiation. The Sun emits radiation over a wide range of energies, with about 2% in the form of high-energy, ultraviolet (UV) radiation. Some of this UV radiation (UV-B) is especially effective in causing damage to living beings, for example, sunburn, skin cancer, and eye damage to humans.

High up in the atmosphere, in a region called the stratosphere between 19 and 30 km above the Earth's surface, ozone is constantly being produced and destroyed naturally. This ozone layer filters out UV rays from the Sun and protects life on Earth. Usually there is a fine balance between the build up and loss of ozone.

Yes, significant depletion of the Arctic ozone layer now occurs in some years in the late winter/spring period (January-April). However, the maximum depletion is generally less severe than that observed in the Antarctic and is more variable from year to year. A large and recurrent “ozone hole,” as found in the Antarctic stratosphere, does not occur in the Arctic.

Scientists expect to detect the recovery of the ozone layer with careful comparisons of the latest ozone measurements with past values. Changes in total overhead ozone at various locations and in the extent and severity of the Antarctic “ozone hole” will be important factors in gauging ozone recovery. Natural variations in ozone amounts will limit how soon recovery can be detected with future ozone measurements.

Measuring the ozone at both poles is a 'barometer' of sorts. Though typically the ozone varies in densities and coverage at these areas, it also reflects the overall warming and depletion of the ozone worldwide. Sun shining on the poles is not filtered of harmful ultraviolet radiation due to the increasing lack of ozone.

No. Because ozone reacts so quickly with contaminants in water and air, it converts back to oxygen within minutes or even seconds. Any ozone molecules that break free from the pool or spa water will convert to oxygen and never reach the atmosphere.

In 1987, the nations of the world banded together to draft the Montreal Protocol to phase out the production and use of CFCs. The 43 nations that signed the protocol agreed to freeze consumption and production of CFCs at 1986 levels by 1990, reduce them 20% by 1994, and reduce them another 30% by 1999. The alarming loss of ozone in Antarctica and worldwide continued into the 1990's, and additional amendments to further accelerate the CFC phase-out were adopted.

Sulfuryl fluoride, the active ingredient in ProFume, is not an ozone-depleting chemical. ProFume contains no chlorine or bromine and, thus, cannot react to deplete stratospheric ozone by the known mechanisms. It is fully oxidized and, thus, is not expected to interact or contribute to local ozone formation (such as smog). When a commodity or facility is aerated, ProFume rapidly dissipates to non-detectable levels. Dow AgroSciences was awarded the Stratospheric Ozone Protection Award by the U.S.

From time to time, people claim that chemicals released from some rockets, in particular NASA's Space Shuttle's Solid Rocket Boosters (SRBs), are responsible for a significant amount of damage to the ozone layer. Studies indicate that they have only a minute impact (less than seven-thousandths of one percent), both in absolute terms and relative to other chemical sources. It is much less than total ozone variability associated with volcanic activity and solar flares.

No. The amount of ozone above a location on the Earth varies naturally with latitude, season, and from day-to-day. Under normal circumstances, the ozone layer is thickest over the poles and thinnest around the equator. The ozone layer over Canada is normally thicker in winter and early spring; it can vary naturally by about 25 per cent between January and July. Weather conditions can also cause considerable daily variations.