The Ozone O3 is protecting us through the Ozone Shield from the harmful ultraviolet UV radiation when it is in the lower portion of the stratosphere at 20km to 30km above Earth. However it is a harmful gas for the respiratory system and it can cause serious health issues when it is inhaled in high consecration.
As a result we divide the Ozone in two categories, the Ozone Shield aka Good Ozone and the Ground Level Ozone aka Bad Ozone. Basically the Ground level Ozone is formatted by a combination of gases and the Sunlight.
VOCs + NOx + Heat + Sunlight = Ozone
Breathing ozone O3 can trigger a variety of health problems, particularly for children, the elderly, and people of all ages who have lung diseases such as asthma. Ground level Ozone can also have harmful effects on sensitive vegetation and ecosystems.
Read more about air pollutants inside my book See The Air