that is located in the stratosphere, approximately 6 to 10 miles (10-17 km) above the Earth’s surface, and is estimated to extend up approximately 30 miles (50 km). The ozone layer protects the Earth and all of its living creatures from the sun’s ultraviolet B (UVB) radiation. Under natural conditions, ozone (O3) is continually being broken down and reformed because it is a highly reactive molecule¹,².
Why is there concern for the ozone layer?
The ozone layer is being deteriorated due to a number of human-produced chemicals that contain chlorine and bromine. With a weaker ozone layer, an increased amount of UVB rays are able to reach the Earth. This increased global level of UVB radiation can lead to an increased risk of human health problems such as cellular DNA damage, skin cancer, and cataracts³,⁴.
The increased level of UVB radiation is also harmful to the plants and animals on our planet. Too much UVB radiation can negatively impact phytoplankton reproduction (a very important part of the global food chain), thereby sending negative impacts throughout the animal kingdom. The reproductive rates of fish, shrimp, crabs, frogs, and salamanders have been found to be negatively impacted by excessive UVB radiation⁵,⁶.
Some crops, such as rice and wheat, are dependent upon cyanobacteria. The cyanobacteria are sensitive to UVB radiation, and can be negatively affected by excessive levels of it. If many plants are killed due higher global levels of UVB radiation, it could dramatically impact our food supply around the world⁶.
Aquatic animals and plants are also being negatively impacted by the excess UVB radiation because UVB rays can penetrate through water and can kill small plants and animals.
What factors affect the ozone layer?
It has been found that both natural and human causes are having impacts on the ozone layer, and it is the human impacts that are having an overall negative impact.
Natural impacts on the ozone layer
Even without humans, solar flares being emitted from the sun would still destroy a certain amount of ozone. This happens when the sun flares protons (positively-charged hydrogen atoms) that reach the Earth’s atmosphere. After a solar flare, a number of chemical reactions occur that break up molecules of nitrogen, water vapor, and ozone in the atmosphere, and the ozone layer is diminished. However, the overall effect is that less than one percent of atmospheric ozone is diminished through these natural processes.
Because the ozone molecules that are broken up are so volatile, they can quickly reform themselves. Therefore, such solar events exert an overall neutral impact on the integrity of the ozone layer. You might say that there is natural resiliency that is built into the ozone layer².
Human impacts on the ozone layer
The primary human pollutants that are deteriorating the ozone layer are chlorofluorocarbons (CFCs), halons, and freons. All three of these classifications of chemicals contain chlorine, and when chlorine is exposed to ultraviolet radiation from the sun, the chlorine atoms are broken apart from the rest of the molecule. Once the chlorine atoms are free, they tear apart ozone molecules and bond with the oxygen atoms. A single atom of chlorine is so reactive that it can destroy more than one hundred thousand ozone molecules⁷.
These chlorine-based chemicals were commonly found in aerosol cans, and were also released by electronic appliances prior to their ban by the industrialized countries in the Northern Hemisphere, including Europe and the U.S.. Although such chemicals have been largely banned throughout much of the world since January 1996, their presence remains in the atmosphere where they continue to wreak their havoc on the ozone layer⁸.
While the amount of chlorine in the atmosphere is now falling, scientists estimate that the elevated levels will remain for at least 50 more years⁹.
Because most countries around the world have phased out ozone-destroying chemicals, the ozone layer isn’t as threatened as it once was. The collaborative process that has taken place to reduce harmful ozone-depleting emissions in the world provides an excellent framework that can also be applied in the reduction of other environmentally-harmful emissions, such as greenhouse gases.