The ozone layer in the Earth's atmosphere protects us from the harmful ultraviolet rays from the Sun, but it is at risk of depletion. This article explains the problem, what is causing it, the international and local efforts to reduce the production and use of ozone depleting chemicals, and how you can help to protect the ozone layer.
Ozone Layer Depletion
The ozone layer is a shield of ozone gas in the stratosphere, between 15 and 35 km above the Earth's surface. The result of a reaction between ultraviolet light from the Sun and oxygen molecules, it stops most ultraviolet (UV) radiation reaching us. However, in 1975 scientists detected a severe drop in ozone levels over Antarctica that repeated each Spring, and by 1987 half of the ozone over the continent had disappeared, creating an enormous "hole" twice the size of the United States. This "hole" in the ozone layer threatens the Earth's environmental balance and human health, with increased cases of skin cancer, eye cataracts and damage to the immune system.
Cause of Ozone Layer Depletion
The stratosphere is being depleted of ozone by man-made chemicals including chlorofluorocarbons (CFCs), halons, methyl chloroform, carbon tetrachloride, methyl bromide, hydrobromofluorocarbons (HBFCs), hydrochlorofluorocarbons (HCFCs) and bromochloromethane (BCM). These chemicals are commonly used as cooling agents for refrigerators and air-conditioners, propellants for aerosol sprays, blowing agents in the manufacture of foam and some plastics, fire retardants for extinguishers and in cleaning agents and solvents in industries. In other words, they are widely used in our everyday lives.
Accelerated Phasing Out of HCFCs
In September 2007, the parties to the 19th meeting of the Montreal Protocol, an international treaty designed to protect the ozone layer, agreed to speed up the phasing out of HCFC use. As a result, Hong Kong must eliminate 75% of its baseline HCFC consumption by 2010 instead of the original 65% and reduce 90% of the baseline consumption by 2015. In 2020, a total ban on the import of HCFCs is to be in place while 0.5% of HCFC consumption may be allowed for servicing of the then existing refrigeration and air conditioning equipment in the period 2020-2030. Such need will be reviewed by the parties concerned in 2015. A crucial aspect of that reduction will involve people like you replacing air-conditioning and refrigeration systems with those that use non-HCFCs refrigerants.
Ozone Layer Protection Ordinance
Hong Kong enacted the Ozone Layer Protection Ordinance (Cap. 403, Laws of Hong Kong) in 1989 to restrict the manufacture, export and import of ozone depleting chemicals. This is achieved through licensing and the registration of related commercial activities. The subsidiary regulations include the Ozone Layer Protection (Products Containing Scheduled Substances) (Import Banning) Regulation and the Ozone Layer Protection (Controlled Refrigerants) Regulation. These two regulations control the import of certain chemicals and their emission to the atmosphere, respectively.The Ozone Layer Protection Ordinance
The Ozone Layer Protection Ordinance applies quotas and licensing restrictions to the import and export of ozone depleting chemicals. Importers of the chemicals listed in the Schedule to the Ordinance must register with the Trade and Industry Department before applying for a licence to receive those chemicals.Scheduled substances under Ozone Layer Protection OrdinanceMore information on licensing control of ozone depleting substances
What You Can Do
Although most ozone depleting substances are used in industry and commerce, what you do at home can still make a difference. The most effective way of protecting the ozone layer is to reduce or even stop using ozone depleting chemicals. You can do this by:
- buying air-conditioners that do not use HCFCs or CFCs as refrigerants;
- regularly inspecting and maintaining your air-conditioners and refrigeration appliances to minimise refrigerant leaks;
- recovering and recycling HCFCs and CFCs in air-conditioners and refrigeration appliances when they are serviced; replacing and retrofitting such equipment to operate on non-HCFC and non-CFC refrigerant should also be considered.
Overall, the best way to help protect the ozone layer is to stop buying all products, big and small, that contain ozone depleting substances. Together we can make a difference.
The ozone layer is a belt of the naturally occurring gas "ozone." It sits 9.3 to 18.6 miles (15 to 30 kilometers) above Earth, and serves as a shield from the harmful ultraviolet B (UVB) radiation emitted by the sun.
Ozone is a highly reactive molecule that contains three oxygen atoms. It is constantly being formed and broken down in the high atmosphere, 6.2 to 31 miles (10 to 50 kilometers) above Earth, in the region called the stratosphere.
Today, there is widespread concern that the ozone layer is deteriorating due to the release of pollution containing the chemicals chlorine and bromine. Such deterioration allows large amounts of ultraviolet B rays to reach Earth, which can cause skin cancer and cataracts in humans and harm animals as well.
Extra ultraviolet B radiation reaching Earth also inhibits the reproductive cycle of phytoplankton, single-celled organisms such as algae that make up the bottom rung of the food chain. Biologists fear that reductions in phytoplankton populations will in turn lower the populations of other animals. Researchers also have documented changes in the reproductive rates of young fish, shrimp, and crabs as well as frogs and salamanders exposed to excess ultraviolet B.
Chlorofluorocarbons (CFCs), chemicals found mainly in spray aerosols heavily used by industrialized nations for much of the past 50 years, are the primary culprits in ozone layer breakdown. When CFCs reach the upper atmosphere, they are exposed to ultraviolet rays, which causes them to break down into substances that include chlorine. The chlorine reacts with the oxygen atoms in ozone and rips apart the ozone molecule.
One atom of chlorine can destroy more than a hundred thousand ozone molecules, according to the the U.S. Environmental Protection Agency.
The ozone layer above the Antarctic has been particularly impacted by pollution since the mid-1980s. This region’s low temperatures speed up the conversion of CFCs to chlorine. In the southern spring and summer, when the sun shines for long periods of the day, chlorine reacts with ultraviolet rays, destroying ozone on a massive scale, up to 65 percent. This is what some people erroneously refer to as the "ozone hole." In other regions, the ozone layer has deteriorated by about 20 percent.
About 90 percent of CFCs currently in the atmosphere were emitted by industrialized countries in the Northern Hemisphere, including the United States and Europe. These countries banned CFCs by 1996, and the amount of chlorine in the atmosphere is falling now. But scientists estimate it will take another 50 years for chlorine levels to return to their natural levels.