Air Contaminants Criteria

Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

Sometimes when we breathe in contaminated or dirty air it can wreak havoc on our body. Continue reading to learn what these contaminants are, why they are so bad for our health, and how they are regulated.

What Are Criteria Air Pollutants?

You rely on the air around you to breathe. Although you can't see it, the air that blankets the earth is made of many different chemicals. What happens when this air is not clean? What contributes to the production of an unclean air environment?

Polluted air due to an industrial factory

Air pollution can be described as dirty air made of unhealthy gases that are dangerous to human health. In 1970, the United States federal government created a law called the Clean Air Act. This act required the environmental protection agency (EPA) to enact a series of air quality standards to keep some very nasty air pollutants dangerous to human health, in check. Specifically, the EPA set in place the National Ambient Air Quality Standards (or NAAQS) for six air pollutants. Those pollutants were:

  1. Particulate matter
  2. Ozone
  3. Carbon monoxide
  4. Sulfur oxides
  5. Nitrogen oxides
  6. Lead

These six pollutants are commonly found in the air and are known as criteria air pollutants. Why did the EPA call them ''criteria?''

In order to determine what pollutant was worthy of making this list a number of studies, both human health and environmental science based, were conducted. From their degree of toxicity on human life to their damage to the environment we live in, these studies led to a series of criteria used to determine the most effective way to regulate them.

Creation of the Clean Air Act and development of these criteria pollutants proved to be a game-changer in the United States as it was now federally supported that states monitor how much of these pollutants were floating in the air.

Monitoring Criteria Air Pollutants

Each criteria air pollutant is regulated by a series of standards that are set by EPA. When you look at these standards you will see that they are often values recorded in ppm (parts per million) or mg/m3.

Let's say you are an environmental health expert. You decide to measure the concentration of criteria pollutants in the air. You set up your air sampling station and begin collecting air samples. If your air concentration of each pollutant exceeds the standard you know you have hit the danger zone.

Illustration of an air sampler for environmental monitoring

Exceeding the standard means there is a high potential of harm to human health and the environment. Thus, measures must be put in place to lower the exposure to a level that is below the standard. How would you know what the best measures would be to protect the environment and public from exposure to these criteria pollutants? Understanding criteria pollutants help public health and environmental scientists determine the best measures to minimize exposure to these pollutants. Let's take a look at each one in greater detail

Criteria Air Pollutants

Particulate matter

This pollutant comes from any different sources such as chemical reactions, the combustion of fuel (i.e. gasoline), industrial processes, and even farming practices such as field burning. Health effects of these tiny particles can range from short-term respiratory problems to long-term heart or lung ailments.

Particulate matter released from incomplete combustion


There is ''good'' and ''bad'' ozone. Natural, good ozone is in the sky above Earth's surface, whereas ground-level ozone is referred to as bad ozone. Ground-level ozone is created when reactive compounds called volatile organic compounds react with nitrogen oxides in the presence of sunlight. This pollutant can create smog and make it hard for a person to breathe and worsen lung diseases such as asthma.

Carbon Monoxide

Have you ever viewed a carbon monoxide monitor in a building or home? An odorless, colorless gas, carbon monoxide is known to be an asphyxiate. Asphyxiates are chemicals that displace oxygen in the lungs depriving vital organs such as the brain from oxygen. In the environment, carbon monoxide is released from the combustion of fuel.

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