Understanding AQI Categories in Under 5 Minutes

The Air Quality Index (AQI) is a standardized system used to communicate daily air quality levels to the public. Developed by the U.S. Environmental Protection Agency (EPA), the AQI focuses on health effects that may be experienced within a few hours or days after breathing polluted air. (epa.gov)

What Does the AQI Measure?

The AQI evaluates 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, but they are all combined into a single, unified index to simplify public understanding. (airnow.gov)

AQI Categories and Their Health Implications

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

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

These categories help individuals understand the potential health risks associated with current air quality levels. (airnow.gov)

How to Use the AQI

Monitoring the AQI can help you make informed decisions about outdoor activities. For instance, on days when the AQI is in the "Unhealthy for Sensitive Groups" category, individuals with respiratory conditions might consider limiting prolonged outdoor exertion. Conversely, during "Good" days, outdoor activities are generally safe for everyone. (cdc.gov)

Staying Informed

To stay updated on local air quality, you can visit the AirNow website, which provides real-time AQI information for locations across the United States. Additionally, many local news outlets and weather services report AQI levels, especially during events that may impact air quality, such as wildfires or high pollen seasons.

Understanding AQI categories empowers you to take appropriate actions to protect your health and the health of those around you.

Highlights:

• Patient Exposure and the Air Quality Index | US EPA, Published on Wednesday, May 20
• How to use the HeatRisk Tool and Air Quality Index | Heat Health | CDC, Published on Wednesday, September 17
• AQI Basics | AirNow.gov