Understanding AQI Categories: A Comprehensive Guide

The Air Quality Index (AQI) is a standardized system used to communicate the quality of air in a specific area and its potential health impacts. Developed by the U.S. Environmental Protection Agency (EPA), the AQI focuses on health effects that may be experienced within hours or days after exposure to polluted air. (epa.gov)

What Are AQI Categories?

The AQI is divided into six color-coded categories, each representing a different level of health concern:

• Good (0–50): Air quality is satisfactory, and air pollution poses little or no risk.
• Moderate (51–100): Air quality is acceptable; however, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
• Unhealthy for Sensitive Groups (101–150): Members of sensitive groups may experience health effects. The general public is less likely to be affected.
• Unhealthy (151–200): Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
• Very Unhealthy (201–300): Health alert: The risk of health effects is increased for everyone.
• Hazardous (301 and higher): Health warning of emergency conditions: everyone is more likely to be affected.

Each category is associated with a specific color, making it easy for individuals to quickly assess the air quality in their area. (airnow.gov)

How Is the AQI Calculated?

The AQI is calculated based on the concentrations of five major air pollutants regulated by the Clean Air Act:

1. Ground-level ozone
2. Particulate matter (PM2.5 and PM10)
3. Carbon monoxide
4. Sulfur dioxide
5. Nitrogen dioxide

Each pollutant has its own AQI scale, and the highest AQI value among these pollutants determines the overall AQI for that location. This approach ensures that the most harmful pollutant at any given time is accurately represented. (aqs.epa.gov)

Health Implications of AQI Levels

Understanding the health implications associated with each AQI category is crucial:

• Good (0–50): Air quality is satisfactory, posing little or no risk.
• Moderate (51–100): Air quality is acceptable; however, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
• Unhealthy for Sensitive Groups (101–150): Members of sensitive groups may experience health effects. The general public is less likely to be affected.
• Unhealthy (151–200): Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
• Very Unhealthy (201–300): Health alert: The risk of health effects is increased for everyone.
• Hazardous (301 and higher): Health warning of emergency conditions: everyone is more likely to be affected.

It's important to note that individuals with respiratory conditions, such as asthma or COPD, may experience symptoms at lower AQI levels. Therefore, staying informed about local air quality is essential for managing health risks. (epa.gov)

Protective Measures During Unhealthy AQI Levels

When the AQI reaches levels categorized as "Unhealthy for Sensitive Groups" or higher, consider the following precautions:

• Limit Outdoor Activities: Reduce the duration and intensity of outdoor exercises, especially for sensitive individuals.
• Stay Indoors: Keep windows and doors closed to prevent outdoor air from entering your home.
• Use Air Purifiers: Utilize air purifiers with HEPA filters to reduce indoor pollutant levels.
• Monitor Local Air Quality: Regularly check local AQI readings to stay informed about air quality changes.

By understanding AQI categories and their associated health risks, individuals can make informed decisions to protect their health and well-being.

Highlights:

• Communicating Air Quality Conditions: The Air Quality Index | US EPA, Published on Monday, September 29
• AQI Basics | AirNow.gov
• AQI