Ozone (O3) is the only air pollutant monitored that is a secondary source pollutant, a product not directly emitted. Ground level ozone is a product of a series of chemical reactions in the atmosphere involving sunlight, oxides of nitrogen, and volatile organic compounds. High temperatures, stagnant wind patterns, and plenty of sunlight contribute greatly to the formation of ozone and thus smog.

Good Up High, Not Nearby

Ozone in the stratosphere ("up high") prevents harmful ultra-violet light rays from penetrating the earth’s upper atmosphere. Ground level ozone ("nearby"), aka smog, produces several health concerns and an increased greenhouse effect.

The National Ambient Air Quality Standards (NAAQS) for ozone, as of October 1, 2015, is 70 ppb (parts per billion) based on an average of the 4th highest eight hour average values over a three year period. 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 — Akron
Chippewa Lake area — Medina
Lake Rockwell — Streetsboro

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.