Ozone Answers

Both ground-level ozone and depletion of the ozone layer cause environmental and health concerns. Ground-level ozone is a pollutant that is harmful to organisms when it is breathed in. Ozone in the troposphere can also cause an increase in surface temperatures. Depletion of ozone in the stratosphere causes health and environmental risks indirectly. Since ozone absorbs UV radiation, having less ozone in the stratosphere means more UV radiation will reach the troposphere. This causes greater risk of skin cancer and cataracts. Changes to global climate and harmful effects to plant life are also concerns.

The ozone layer helps regulate the Earth’s temperature by absorbing a large percentage of the UV radiation entering the atmosphere. This protects living organisms from exposure to large amounts of UV radiation, maintains livable climates, and regulates the amount of harmful ground-level ozone.

The ozone layer absorbs a large portion of incoming UV radiation, which keeps ground-level ozone from forming. A higher percentage of UV radiation entering the troposphere would allow a greater amount of ozone to form in the troposphere. Ozone is a pollutant in the troposphere. By regulating the amount of UV radiation that enters the troposphere, the ozone layer also regulates the amount of ozone formation in the troposphere.

Ultraviolet radiation breaks the bond between two oxygen atoms in an oxygen molecule, leaving two free oxygen atoms. When one of these free oxygen atoms combines with an existing oxygen molecule, it forms a molecule composed of three oxygen atoms, known as ozone.

The chlorine in chlorofluorocarbons is broken from the molecule by ultraviolet radiation. The free chlorine then combines with an oxygen atom from ozone, leaving an oxygen molecule and forming chlorine monoxide. Free molecules of oxygen can displace the chlorine in chlorine monoxide, leaving chlorine free to break up another molecule of ozone. One chlorine atom can destroy up to 100,000 ozone molecules.

CFCs can remain in the atmosphere long enough to reach the stratosphere. There, ultraviolet radiation breaks them apart and releases chlorine atoms. A chlorine atom reacts with ozone, converting it to oxygen, and is then regenerated in the reaction cycle. Because it can repeat this process many times, a small amount of CFCs can lead to the destruction of a large amount of ozone.

The ozone layer absorbs much of the Sun’s harmful ultraviolet radiation, especially UV-B, before it reaches Earth’s surface. This limits damage to cells and DNA, helping protect people, other animals, plants, and ocean ecosystems and allowing life to thrive.

Ultraviolet radiation from the Sun splits oxygen molecules (O₂) into individual oxygen atoms. An oxygen atom can then combine with an O₂ molecule to form ozone (O₃). Sunlight also breaks ozone apart, so ozone is continually formed and destroyed in the stratosphere.

The ozone layer absorbs much of the Sun’s ultraviolet radiation before it reaches the lower atmosphere. This limits UV-driven chemical reactions that can form ground-level ozone and other air pollutants, helping maintain air quality near Earth’s surface.

Ground-level ozone is an air pollutant that can irritate the lungs, worsen asthma, and damage crops and other vegetation. Ozone layer depletion is different: it allows more harmful ultraviolet radiation to reach Earth, increasing risks such as skin cancer and cataracts and harming plants, plankton, and ecosystems. Ground-level ozone directly degrades air quality, while ozone depletion increases exposure to UV radiation.