Glossary:Ozone

Ozone (or trioxygen) is an inorganic molecule with the chemical formula O3. It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O2, breaking down in the lower atmosphere to O2 (dioxygen). Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere. It is present in very low concentrations throughout the latter, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun's ultraviolet (UV) radiation.

Ozone is a powerful oxidant (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. This same high oxidizing potential, however, causes ozone to damage mucous and respiratory tissues in animals, and also tissues in plants, above concentrations of about 0.1 ppm. While this makes ozone a potent respiratory hazard and pollutant near ground level, a higher concentration in the ozone layer (from two to eight ppm) is beneficial, preventing damaging UV light from reaching the Earth's surface.

While the largest emissions from oil and gas development (methane and ethane) are not contributors to ozone formation according to the EPA, the other nine chemicals on the list are classified as volatile organic compounds (VOCs). When VOCs are combined with nitrogen oxides (NOx) and sunlight, they will demonstrate varying reactivity rates, and given enough time can lead to ozone formation. High levels of ozone can cause respiratory issues, particularly in sensitive populations and those with asthma. Due to these health impacts, Colorado has regulations in place to reduce VOC and NOx emissions from oil and natural gas industry, as well as emissions from other contributors, such as cars, boats, lawnmowers and even paints.