Ozone (O3)

Background

Ozone is the only air pollutant monitored that is a secondary source pollutant, a product not directly emitted. Ozone is a resultant product of a series of chemical reactions in the atmosphere involving sunlight, oxides of nitrogen, and volatile organic compounds. High temperatures and stagnant wind patterns contribute greatly to the formation of ozone and thus smog. Ozone not only contributes to smog and an increased greenhouse effect but it also prevents harmful ultra-violet light rays from penetrating the earth's upper atmosphere.

The National Ambient Air Quality Standards (NAAQS) for ozone, as of June 2011, is 75 ppb (parts per billion) based on an average of the 4th highest eight hour average values over a three year period. The standard is currently being considered for revision (7/2011). The EPA only requires that ozone be monitored for the time period of April 1 to October 31 each year. The reason for this time frame is that certain meteorological criteria, typically not present in the winter months in Ohio, must be present for the formation of ozone to occur. 

ARAQMD monitors ozone at three sites: Patterson Park, Medina, and Lake Rockwell.

More in depth information about ozone is available through the EPA including basic information, health and environment, standards, designations, implementation, regulatory actions, trends, sources, early action compacts, and other resources.


Trends