The good, the bad and the ugly about ozone

When the sun comes out, temperatures go up and there is air pollution, ozone formation occurs.

The atmospheric layers around the Earth and where ozone is located. Photo: Environmental Protection Agency l MSU Extension

The atmospheric layers around the Earth and where ozone is located. Photo: Environmental Protection Agency l MSU Extension

Summer is sunshine and warm temperatures for enjoying outdoor activities. But, while everyone loves these hot, sunny, summer days (especially after the winter we experienced!), it also can mean an increase in the formation of ozone.

Ozone (O3), the primary ingredient in smog, is a gas that is formed through the chemical reaction between oxides of Nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight.

There is both “good” and “bad” ozone, depending on its location in the atmosphere. Ozone occurs in two regions of the atmosphere; the tropospheric layer or ground level ozone is where the bad ozone forms. Both types of ozone have the same chemical composition.

The ground level or bad ozone is an air pollutant that is harmful to breathe, especially if a person has respiratory issues. While the average adult breathes in over 3000 gallons of air daily, children are even more at risk because their lungs are still forming, they breathe in more air daily, are more susceptible to air pollution and tend to be more active outdoors during hot, sunny days. It can also damage trees, crops and other forms of vegetation and ecosystems. Emissions from motor vehicles, gas vapors, chemical solvents and industrial facilities and electric utilities are the main sources of NOx and VOCs.

While ozone pollution is a major concern during the summer, it can occur during winter months in some southern or mountain regions if conditions are right. Wind also transports ozone long distances to non-traditional ozone areas, such as rural or less densely-populated locations.

The tropospheric layer, where “bad” ozone is created, extends approximately six miles up from the Earth’s surface where it meets the stratospheric layer.

The good ozone is found in the stratospheric layer of the atmosphere. Ozone in this layer is produced naturally. This ozone layer protects the Earth from the sun’s damaging ultraviolet (UV) radiation. This UV radiation can lead to increases in skin cancer, cataracts and immune system impairment.

This protective shield, however, is being destroyed by the man-made chemicals from the tropospheric layer referred to as ozone depleting substances (ODS). These substances, once released, degrade very slowly and can remain viable for years as they move up through the troposphere to the stratosphere where the ODS break down forming chlorine and bromine molecules. These molecules are what destroy the protective stratospheric ozone layer.

Because ODS can remain intact for many years, citizens need to take steps to reduce ODS to reduce the bad ozone and protect the good ozone. For suggestions on ways to reduce air pollution, see the Michigan State University Extension article, What are Ozone Action Days?

For more information about air quality and ozone or to join the Michigan EnviroFlash Program, visit the Department of Environmental Quality website.

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