What is the difference between ozone in the stratosphere and ozone in the troposphere? Which is a pollutant, and which protects terrestrial life?

The stratosphere is one of the primary layers of Earth's atmosphere, located above the troposphere and below the mesosphere. This layer extends from about 10 km (6 miles) to 50 km (31 miles) above Earth's surface.
One of the key features of the stratosphere is the presence of the ozone layer, which absorbs and scatters ultraviolet (UV) radiation from the sun. The temperature in the stratosphere also increases with altitude due to the absorption of UV radiation by ozone, resulting in a relatively stable and stratified layer.
This stable atmospheric layer is less turbulent than the troposphere and plays a crucial role in protecting life on Earth from harmful solar radiation. Without the ozone in the stratosphere, life as we know it would be impossible due to the high levels of UV radiation reaching the surface.

The troposphere is the lowest layer of Earth's atmosphere, stretching from the planet's surface up to about 8-15 km (5-9 miles) depending on the latitude.
This layer is where all weather phenomena occur, including clouds, rain, and storms. The temperature in the troposphere generally decreases with altitude, leading to a dynamic and turbulent environment.
Due to its proximity to Earth's surface, the troposphere contains approximately 75% of the atmosphere's mass and most of its water vapor. Human activities, such as burning fossil fuels and industrial processes, often release pollutants into the troposphere. This can lead to the formation of ground-level ozone, which is harmful to human health and ecosystems.

The ozone layer is a vital component of the stratosphere, situated between 15 km (9 miles) and 35 km (22 miles) above Earth's surface. This layer contains a high concentration of ozone (O₃) molecules.
The primary function of the ozone layer is to absorb and scatter the sun's ultraviolet (UV) radiation, particularly UV-B and UV-C rays. These forms of radiation can cause significant harm to living organisms, including skin cancer, cataracts, and immune system suppression in humans, as well as DNA damage in plants and animals.
By blocking the majority of these harmful rays, the ozone layer serves as Earth's natural sunblock. However, human activities have led to the depletion of this layer, notably through the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances.

Air pollution refers to the presence of harmful substances in the atmosphere, which can be natural or human-made. Common pollutants include particulate matter, carbon monoxide, sulfur dioxide, nitrogen oxides, and volatile organic compounds.
One of the consequences of air pollution is the formation of ground-level ozone in the troposphere. When pollutants from vehicle emissions and industrial activities react with sunlight, they produce ozone, a major component of smog.
This type of ozone is not beneficial and poses health risks, such as respiratory issues, cardiovascular diseases, and environmental damage. Reducing air pollution is essential to improve air quality, mitigate climate change, and protect human health and ecosystems.

Ultraviolet (UV) radiation is a type of electromagnetic radiation emitted by the sun. It is classified into three types based on wavelength: UV-A, UV-B, and UV-C.
UV-A has the longest wavelength and primarily causes skin aging and indirect DNA damage. UV-B has a shorter wavelength and is responsible for direct DNA damage, leading to skin cancer and sunburns. UV-C has the shortest wavelength and is the most harmful, but it is mostly absorbed by the ozone layer and does not reach Earth's surface.
The ozone layer plays a critical role in protecting life by absorbing most of the sun's harmful UV-B and UV-C radiation. Prolonged exposure to UV radiation can have serious health effects on humans and negative impacts on other organisms and materials, making it vital to maintain the integrity of the ozone layer.