Understanding the Air Quality Index (AQI) Categories

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 the 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 air quality levels in their communities. (epa.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:

• Ground-level ozone
• Particulate matter (PM₂.₅ and PM₁₀)
• Carbon monoxide
• Sulfur dioxide
• Nitrogen dioxide

Each pollutant has its own AQI scale, and the highest AQI value among these pollutants determines the overall AQI for a location. This approach ensures that the AQI reflects the pollutant that is most likely to harm public health at a given time. (airnow.gov)

Why Is the AQI Important?

Understanding the AQI is crucial for protecting public health. It provides a clear and concise way to communicate air quality levels, helping individuals make informed decisions about outdoor activities. For instance, during periods when the AQI is categorized as "Unhealthy for Sensitive Groups" or higher, sensitive individuals—such as those with respiratory conditions—should consider limiting prolonged outdoor exertion. (epa.gov)

How Can You Monitor the AQI?

Monitoring the AQI is straightforward. The EPA provides real-time AQI data through platforms like AirNow.gov, where you can check current air quality levels for your area. Additionally, many local health departments and environmental agencies offer AQI information on their websites and through mobile applications. Regularly checking the AQI can help you plan outdoor activities and take necessary precautions when air quality is poor. (airnow.gov)

By staying informed about the AQI, you can take proactive steps to protect your health and the health of those around you.

Highlights:

• IQAir implements 2024 update to U.S. EPA Air Quality Index (AQI) | Knowledge Base | IQAir USA, Published on Sunday, May 05