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Air Quality in Indiana

Air Quality in Indiana > Air Quality 101 > March 2013: Introduction March 2013: Introduction

If a lie is told often enough, it becomes the truth. I’m not sure who originally said this, but they were right. A story is currently circulating that Indiana has some of the worst air quality in the nation. It is not true, but people are beginning to believe it, and they should not.

Every other week I intend to publish information about air quality in general and how it applies to Indiana. This is the first article.

Some of the topics I plan to cover are: what air pollution is, what air quality standards are, how we know what air quality levels are, and how we compare to levels in other states. Each issue I will cover a single topic and hopefully over time build up information that covers most areas within the air pollution field. I will include links to help the reader find additional information or to provide sources to verify some of the data included in the column.

As this develops I would like to hear from you. It will take time, but I hope to explain how things work in the air pollution field as they relate to Indiana. When I miss the mark I need to know, but when I hit the target I also need to know. I can be reached at

So let us start by defining what air pollution is. Indiana Code 13-11-2-5 provides this definition: “Air pollution, for purposes of air pollution control laws and environmental management laws, means the presence in or the threatened discharge into the atmosphere of one (1) or more contaminants in sufficient quantities and of the characteristics and duration that:

  1. is injurious to or threatens to be injurious to human health, plant or animal life, or property; or
  2. interferes unreasonably with the enjoyment of life or property.”

Legal definitions often raise more questions than they answer, and I think this is the case with the definition of air pollution. Essentially there are four groups of air pollutants:

  1. criteria pollutants
  2. hazardous air pollutants
  3. gases that destroy the stratospheric ozone layer
  4. greenhouse gases

Criteria pollutants are pollutants that the United States Environmental Protection Agency (U.S. EPA) has determined have health impacts and has established national ambient air quality standards specific to these compounds. These include: particles in the air with a diameter less than 10 microns (PM-10), particles in the air with a diameter less than 2.5 microns, sulfur dioxide, nitrogen dioxide, ozone, carbon monoxide and lead. For reference purposes, the diameter of a human hair is 50 to 75 microns. Thus U.S. EPA is aiming to limit small particles that can be taken deeply into the lungs and cause damage.

U.S. EPA defined hazardous air pollutants and published a list of 189 specific compounds or categories of compounds that are of concern. This list has changed slightly over time. A later issue will discuss this topic in more detail, but hazardous air pollutants (HAPs) can cause cancer or other health effects. U.S. EPA does not set ambient standards for HAPs, but evaluates the impacts of these pollutants based upon risk assessments.

A group of chemicals destroys the ozone layer high above the earth that protects us from ultraviolet radiation. U.S. EPA has identified these chemicals and banned or limited their use.

Greenhouse gases are a select group of gases that cause the atmosphere to warm due to their presence. The most common one is carbon dioxide. A later issue will discuss these pollutants and their impacts.

Air pollution is not a new topic. Smokey air was a chronic public health problem in centuries past. As wood became scarce and expensive in the growing city of London, people began burning sea-coal, which was soft and created more smoke than fire or heat. As far back as 1300, King Edward I stated, “Be it known to all within the sound of my voice, whosoever shall be found guilty of burning coal shall suffer the loss of his head.” In 1948, there was a serious air pollution episode in Donora, Pennsylvania, and in 1952, in London. Soon after that, real progress in air pollution control began to take shape. In 1963, the U.S. passed the first Clean Air Act. In 1970, the Clean Air Act was amended and the U.S. EPA was created.

More information on air pollution can be found on the U.S. EPA website. Origins of modern air pollution are covered in the U.S. EPA online air pollution control course and historical topics are provided.

A glossary of air pollution terms can be found on the IDEM Air Toxics Program website.

We will focus next issue on criteria pollutants, including how U.S. EPA establishes national ambient air quality levels. Until next time.

Keith Baugues