Ozone, Good Up High, Bad Nearby. Ozone is the same whether it is high altitude or ground-level. However, it protects us high above the earth but can be bad for us to breathe near the ground. Though it acts as a protective layer high above the earth, ozone can be harmful to breathe, it is the prime ingredient of smog in our cities.
Many urban areas tend to have high ozone levels.
However, areas downwind of urban settings are also subject to high ozone exposure as winds carry VOCs and NOx from their original sources. When inhaled, ozone can damage the lungs. Relatively low amounts of ozone can cause chest pain, coughing, nausea, throat irritation, and congestion. It may also worsen bronchitis, heart disease, emphysema, and asthma. Healthy people as well as those with respiratory problems, experience breathing problems when exposed to ozone.