Skip directly to searchSkip directly to the site navigationSkip directly to this page's context menuSkip directly to the page's main content

Indicator Report - Air Quality: Ozone

Why Is This Important?

Ozone is a naturally occurring component of the earth's atmosphere at ground level and in the upper regions of the atmosphere. While upper atmospheric ozone protects the earth from the sun's harmful rays, ground-level ozone can be detrimental to the health of plants, animals, and human beings.

Molecules of ozone are made up of three oxygen atoms (O3) and are chemically identical in the upper atmosphere and at ground level. The lungs of animals and humans have a thin liquid lining that protects lung tissue from normal amounts of ozone. However, sunlight and heat can create new ground-level ozone molecules from nitrogen oxides and volatile organic chemicals that are found naturally at the earth's surface, as well as in emissions from industrial facilities, electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents in urbanized regions. Ozone is a principle component of urban smog and is measured in parts per million (ppm).

Ozone can cause several adverse health effects in anyone, but especially in sensitive populations such as children, older adults, people with preexisting lung diseases such as asthma, and people who are physically active outdoors. Some of these health problems include painful breathing, chest tightness, headache, coughing, increased asthma symptoms, lung inflammation, and temporary reduction in lung capacity. Over time, ozone is associated with chronic lung problems and respiratory infections. Adverse health effects from ozone are more likely to occur when ozone levels exceed the EPA's standard, but are possible when ozone levels are below the standard, especially in sensitive populations.

Ground-level ozone, not to be confused with the atmosphere's protective ozone layer, is created by reactions between environmental pollutants, light, and heat. Ozone is the main component of smog and is dangerous to health and the environment. The creation of ozone is facilitated by warm weather and sunshine; therefore, ozone levels are usually higher in the summer and in the mid-afternoon.

Climate change may play a part in the creation of more ground-level ozone pollution. As temperatures increase, it is expected that the number of high ozone days will increase, since heat accelerates the nitrogen oxide and volatile organic compound reaction [4]. Researchers have found that a combination of higher temperatures, sunlight, emissions, and air stagnation events (i.e., inversions) may result in an increase of ozone levels. However, more research is needed to accurately gauge what portion of ozone is actually increasing solely due to climate change.

Maximum 8-hour Average Ozone Concentrations Over the National Ambient Air Quality Standard, Number of Days by County, Utah, 2001-2011

::chart - missing::
data tableconfidence limits

Data Notes

These data include "exceptional events", such as high winds, fires, construction, fireworks, etc.

Data Sources

U.S. Environmental Protection Agency, Air Quality System (AQS).

Other Views


The United States' Environmental Protection Agency (EPA) ozone standard states that the 8-hour average ozone level should not exceed 0.075 ppm. These standard levels are often referred to as the National Ambient Air Quality Standards (NAAQS). This level is considered protective for most people and within the normal defensive capacities of the human respiratory system [1-3].

How We Calculated the Rates

Numerator: This Indicator Report contains the following variables: 1. Number of days with maximum 8-hour average ozone concentrations above the National Ambient Air Quality Standards (NAAQS) by county 2. Number of person-days with maximum 8-hour average ozone concentrations above the NAAQS by county
Denominator: When applicable, population was obtained from the IBIS query system for appropriate years by county.

Page Content Updated On 04/06/2015, Published on 04/10/2015
The information provided above is from the Utah Department of Health's Center for Health Data IBIS-PH web site ( The information published on this website may be reproduced without permission. Please use the following citation: "Retrieved Mon, 06 July 2015 5:39:52 from Utah Department of Health, Center for Health Data, Indicator-Based Information System for Public Health Web site:".

Content updated: Tue, 19 Nov 2013 23:09:26 MST