St. Louis Air Quality by St. Louis Regional Clean Air Partnership

Sources of Ozone

Unlike most other pollutants, ozone is not significantly emitted directly into the air by specific sources. Ozone is generated when heat and sunlight "cook up" Nitrogen Oxides and Volatile Organic Compounds (VOC) to create ozone.

Ozone and its precursors can travel with the wind. Because of this, ozone cannot be viewed as a strictly local problem, but more as a regional issue that must be dealt with not only by the people in the highly urbanized St. Louis area, but also by people throughout the Bi-State region.

The sources of VOCs can be split into four main categories:

Point sources are large stationary sources (e.g., power plants, chemical plants, major manufacturing sites).

Area sources are sources which, when viewed individually, do not have large enough emissions to warrant individual tracking, but in the aggregate may significantly contribute to emissions (e.g., small businesses such as dry cleaners or printers, vehicle refueling operations, open burning, lighter fluid, painting).

Mobile sources are vehicles traveling on public roads.

Off-road or non-road mobile sources are aircraft, rail, marine vessels, farm and construction equipment, lawn and garden equipment and other such machinery.

St. Louis Sources of VOCs 1990
St. Louis sources of VOCs in 1990 pie graph

source: MDNR and IEPA

Typically, ozone pollution is a problem in the St. Louis area in the hot summer months (from late May to early September) when the sun is strong and can cause the chemical reaction to take place. Ozone levels tend to rise in mid-morning, several hours after the rush-hour and onset of emissions-generating business operations (as many businesses only operate one shift per day) and peak in the late afternoon.

Missouri State plans to reduce emissions from a range of sources are required under the Clean Air Act Amendments of 1990.

Air Pollution Basics

Sources of Ozone

About Air Pollution Subcategories