Ozone depletion refers to the slow decline in the amount of ozone in the Earth’s stratosphere since the late 1970′s. This post will look at the causes of ozone depletion, and then talk about the consequences of ozone depletion.
Causes of Ozone Depletion
Humans are responsible for the decline in the amount of ozone in the atmosphere. Thomas Midgley invented chlorofluorocarbons (CFC’s) in the 1920′s. By the 1970′s they were used in many different products, including air-conditioners, insecticide, paint and deodorants. CFC’s take about 15 years to reach the stratosphere, and stay there for about 100 years. In this time they destroy up to 100,000 molecules of ozone! Other halons (chemicals that contain chlorine and/or bromine) have also contributed to ozone depletion, but CFC’s are the main cause. Polar stratospheric clouds over the Antarctic contribute to extremely low seasonal drops in ozone levels. This is called an ‘ozone hole’.
Consequences of Ozone Depletion
- The ozone layer stops harmful UV rays from reaching the Earth. The depletion of ozone means that more harmful UV rays get through. This has the potential to cause more skin cancers.
- Rice crops could be affected by ozone depletion. They depend on cyanobacteria for retention of nitrogen. Cyanobacteria are very sensitive to UV light, so the increase might kill them.
- Plankton are also sensitive to UV light and could become extinct if UV levels are too high.
- Increases the levels of ozone in the troposphere. While it is helpful in the stratosphere, it is harmful to human health in the troposphere, as it can cause asthma attacks. It also attacks rubber in car tyres.
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