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Jul 20

What is the Air Quality Index (AQI)?

Posted on July 20, 2023 at 3:54 PM by Riley Cole

Hazy view of trees with 'air quality index' text

At Linn County Public Health, our air quality branch is responsible for ambient air monitoring for various pollutants, including particulate matter, ozone, and sulfur dioxide. Due to risks associated with human health and the environment, the Clean Air Act requires the United States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for these types of pollutants. So, what does the Air Quality Index (AQI) tell us about air quality and health risks? 

About the AQI
The AQI is a measure of pollution in the air and contains various categories and associated health effects. Each criteria pollutant (i.e., particulate matter, ozone, and sulfur dioxide) has associated health effects based upon varying concentrations in the air. Linn County Public Health uses air monitoring equipment to track these types of pollutants - right here in Linn County. The AQI levels are useful in determining an overview of the current air quality, how concerning the air quality is, and actions individuals can take to protect themselves.

AQI table with different levels and descriptions

Graphic Source:

Individuals are able to monitor the AQI from anywhere at any time, as the air quality branch has a monitoring website that makes it easy for residents to know what the current AQI is. Additionally, is another website that provides real-time updates for individuals to know the AQI. On, individuals can put in their zip code and see the AQI right where they are.

About Health Risks

Both particulate matter and ozone can affect the lungs and be problematic for at-risk populations, such as those with preexisting respiratory conditions (i.e., asthma, emphysema, and chronic obstructive pulmonary disease (COPD)), children, older adults, pregnant women, outdoor workers, and people with heart disease. Health effects are varied depending upon which pollutant is impacting air quality:

  • Health effects of ozone pollution: cause coughing and sore or scratchy throat, make it more difficult to breathe deeply and vigorously, cause pain when taking a deep breath, inflame and damage airways, make the lungs more susceptible to infection, aggravate lung diseases like asthma, emphysema, and chronic bronchitis, and increase the frequency of asthma attacks.
  • Health effects of particulate matter: can affect your lungs and heart, cause premature death in people with heart or lung disease, cause nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function, and increase respiratory symptoms like irritation of the airways, coughing, or difficulty breathing.

In the event the AQI is high, Linn County Public Health and additional air-monitoring partners, such as the Iowa Department of Natural Resources (DNR) and National Weather Service, will issue an air quality alert. Anytime an air quality alert is issued, individuals should follow appropriate recommendations until the AQI levels improve to a normal range. Based on the AQI, there are certain recommendations for individuals to follow, depending on the concentration of pollutants detected in the air. The EPA has specific guides individuals can follow in the event there are high ranges of particulate matter or ozone in the air:

Individuals are encouraged to follow Linn County Public Health on Facebook and Twitter to receive updates about air quality. Additionally, individuals can sign up to receive email or phone notifications when an air quality alert is issued by Linn County Public Health.

By staying air aware, such as knowing the AQI and following recommendations, Linn County Public Health and local residents can work together to be safe and healthy, especially during air quality events.