Ground Level Ozone
Ground Level* Ozone (O3) is harmful to health. Ozone is not directly emitted, but is formed by a complex set of reactions involving NOx and volatile organic compounds, usually some distance away from the source. Due to these reactions, ozone levels are actually lower next to busy roads, yet higher in rural locations than in cities. Once formed, ozone can remain in the atmosphere for many days and is often transported over long distances. (*As opposed to stratospheric ozone present in the “ozone layer” which is beneficial as it prevents dangerous radiation from the sun damaging life on Earth)
Ozone can irritate the respiratory system. This might come in the form of coughing or an uncomfortable feeling in the chest. Symptoms may last a few hours after exposure. Ozone can aggravate asthma. High ozone levels result in a greater number of asthma attacks; this is because asthmatics are more affected by the irritant. Ozone also makes people more sensitive to allergens that cause asthma attacks. There is a concern that the developing lungs of children repeatedly exposed to high levels of ozone may be damaged. Some studies in animals suggest that ozone may also harm the ability to fight off respiratory infections.