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 the second major layer of Earth's atmosphere, situated above the troposphere and below the mesosphere. It extends approximately 10 to 50 kilometers (6 to 31 miles) above Earth’s surface. This layer is crucial due to its content of ozone gas, which forms the ozone layer.
The ozone layer within the stratosphere serves an essential function by absorbing a large portion of the Sun's harmful ultraviolet (UV) radiation. This absorption process helps to prevent excessive UV radiation from reaching the Earth's surface, which can cause skin cancer, cataracts, and other health issues in humans, as well as harming plant life and ecosystems.

The troposphere is the lowest layer of Earth's atmosphere, extending from Earth's surface up to around 10 kilometers (6 miles) high, depending on the location and weather. This layer contains about 75% of the atmosphere's mass and is where nearly all weather events occur, including clouds, rain, and storms.
Ozone present in the troposphere is quite different from that in the stratosphere. Here, ozone is considered a pollutant and is harmful to humans. It's formed through chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) under sunlight. This ozone contributes to smog and can cause respiratory problems and other health issues.

Ozone pollution occurs mainly in the troposphere, close to the Earth's surface. Unlike the beneficial ozone in the stratosphere, tropospheric ozone is a harmful pollutant. It forms from reactions between pollutants like nitrogen oxides (NOx) and volatile organic compounds (VOC), often emitted from vehicle exhausts, industrial facilities, and chemical solvents, in the presence of sunlight.
High levels of tropospheric ozone can lead to severe health and environmental effects. It can cause respiratory problems, aggravate asthma, reduce lung function, and harm plant life by reducing their growth and survival. It is a major component of urban smog and can significantly affect air quality.

Ultraviolet (UV) radiation protection is one of the critical roles of the stratospheric ozone layer. UV radiation from the sun includes UV-A, UV-B, and UV-C rays, with UV-B and UV-C being particularly harmful to life forms. The ozone layer absorbs approximately 97-99% of this harmful UV radiation.
By filtering out these dangerous rays, the ozone layer helps to prevent skin cancers, cataracts, and other health issues in humans, as well as protecting wildlife and plants. Without this protective barrier, life on Earth would be much more vulnerable to the harmful effects of UV radiation, significantly impacting ecosystems and human health.