Some human activities release chemicals into the air that remove ozone. Less ozone in the atmosphere increases the amount of ultra-violet (particularly UV-B) rays that reach the earth. Sunburning UV-B is harmful to people and the environment.
Ozone (O3) is an atmospheric gas found mainly in the upper atmosphere. The ozone layer forms a natural screen that absorbs most of the ultraviolet (UV) radiation from sunlight – before it reaches the earth’s surface.
During the 1980s and 1990s there was a decreasing trend in the ozone concentration over New Zealand which has since stabilised since the 2000s, similar to international trends. During early spring, an ozone ‘hole’ has formed over Antarctica since the late 1970s. Although the hole itself doesn’t move, when the ozone layer rebuilds itself during late spring and early summer the total ozone layer over the Earth gets diluted (reduced).
In New Zealand it’s estimated that ozone losses since 1980 have caused sunburning radiation to increase by 10 to 12 percent (1996 levels).
Increasing ultraviolet (UV) radiation can cause:
- Health problems for people and animals - more skin cancer, eye damage and damage to the immune system (increasing vulnerability to diseases).
- Reduced plant growth - increased UV radiation can reduce plant photosynthesis and growth.
- Genetic changes - small organisms may have an increased chance of mutation.
- Damage to possessions - materials sensitive to ultra-violet light may age quicker.
Ozone naturally breaks down and re-forms itself in the upper atmosphere. However, except for areas near the equator, ozone is now being destroyed much faster than it’s being created. The main culprits are synthetic (human-made) chemicals containing bromine and chlorine, such as chlorofluorocarbons (CFCs). CFCs were used as refrigeration agents and propellants in aerosol sprays. Some existing refrigeration systems still contain this chemical.
Other ozone-depleting chemicals include:
- carbon tetrachloride
- methyl bromide
- methyl chloroform
These chemicals have a range of uses, for example, methyl bromide is used as a fumigant for treating primary products for export such as timber (and imported products) to control quarantine pests.
In 1998 the New Zealand Government adopted the Montreal Protocol on 'Substances which Deplete the Ozone Layer'. This international protocol called for a freeze of annual use of CFCs to 1986 levels and a reduction in use by 50 percent by 1999.
New Zealand’s Government controls the import and sale of CFCs and halons, and technology and goods made using CFCs. Find out more about the Ozone Layer Protection Act 1996 (Ministry for the Environment).
You can help to reduce the amount of CFCs entering the atmosphere by:
- Disposing of your old refrigerator properly to make sure CFCs aren’t released into the air - recycling depots usually have a place for old refrigerators.
- Maintaining your car’s air conditioning system so it doesn’t leak CFCs.
New Zealand has a very high rate of melanoma – the deadliest form of skin cancer. We are exposed to high levels of UV, particularly in summer. It’s important to reduce our exposure to UV by:
- avoiding the sun between 11:00am to 4:00pm - particularly during summer
- using sunscreen sun protection factor (SPF) 15 to 30+
- using wrap-around sunglasses to protect your eyes
- staying in the shade when outside
- wearing sun-protective clothing, such as hats and long sleeved shirts.
The Cancer Society has more information on how to protect yourself from UV rays.