What is ozone

What is Ozone?

Ozone is a colorless gas with the chemical formula O₃, meaning it consists of three oxygen atoms bonded together. While oxygen (O₂) is the form we breathe, ozone is a highly reactive variant that plays a crucial role in Earth's atmosphere. The term "ozone" comes from the Greek word "ozein," meaning "to smell," reflecting the sharp odor that accompanies its presence.

Stratospheric Ozone

The ozone layer exists primarily in the stratosphere, approximately 10-50 kilometers above Earth's surface. This natural concentration of ozone creates a protective barrier that absorbs the sun's ultraviolet (UV-B) radiation before it reaches the planet's surface. This protection is vital for life on Earth, as excessive UV-B exposure can cause skin cancer, cataracts, immune system suppression, and damage to marine ecosystems. The ozone layer absorbs about 97% of the sun's medium-frequency ultraviolet radiation.

How Ozone Forms

In the upper atmosphere, oxygen molecules (O₂) are split apart by ultraviolet radiation from the sun. These freed oxygen atoms then recombine with other oxygen molecules to form ozone (O₃). This process is continuous and creates a natural balance in the stratosphere. Lightning strikes can also produce ozone in the lower atmosphere, which is why people often notice the distinctive smell after thunderstorms.

Ground-Level Ozone Pollution

Unlike stratospheric ozone, ground-level ozone is a harmful air pollutant. It forms through chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Sources include vehicle emissions, industrial facilities, and power plants. Ground-level ozone contributes to smog and respiratory problems in humans, particularly affecting children, elderly people, and those with asthma or other lung conditions.

The Ozone Layer Crisis and Recovery

Starting in the 1970s, scientists discovered that chlorofluorocarbons (CFCs) and other chemicals used in refrigerators and aerosol sprays were damaging the ozone layer. These substances released chlorine atoms in the stratosphere, which destroyed ozone molecules. This discovery led to the Montreal Protocol in 1987, an international treaty banning ozone-depleting substances. Thanks to this global effort, the ozone layer has been gradually recovering, though it is still expected to take decades to fully restore to pre-1980 levels.