Understanding Fine Particulate Matter (PM2.5)
PM2.5 (Particulate Matter 2.5) refers to microscopic particles in the air that are 2.5 micrometers or less in diameter. Because they are so small—about 30 times smaller than a human hair—they are considered the most hazardous pollutant, as they can penetrate deep into the lungs and affect overall health. PM2.5 levels are the primary factor used globally to assess air quality risk.
Units of Measurement: Micrograms per Cubic Meter (µg/m³)
Air pollution concentration is typically measured in micrograms per cubic meter (µg/m³). This unit describes the mass of pollutants (like PM2.5, PM10, or ozone) present within one cubic meter of air. A higher µg/m³ reading indicates a greater concentration of harmful particles, which translates directly to a higher health risk and a worse Air Quality Index (AQI) score.
The Air Quality Index (AQI) Scale: 0 to 500
The Air Quality Index (AQI) is a standardized scale used by government agencies to communicate current air quality levels to the public, ranging from 0 to 500. This index simplifies complex pollutant data into a single, easy-to-understand number, with corresponding color codes to indicate health risk.
| AQI Range | Category | Color Code | Health Implication |
|---|---|---|---|
| 0 - 50 | Good | Green | Air quality is considered satisfactory, and air pollution poses little or no risk. |
| 51 - 100 | Moderate | Yellow | Air quality is acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people. |
| 101 - 150 | Unhealthy for Sensitive Groups | Orange | Members of sensitive groups may experience health effects. The general public is less likely to be affected. |
| 151 - 200 | Unhealthy | Red | Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects. |
| 201 - 300 | Very Unhealthy | Purple | Health warnings of emergency conditions. The entire population is more likely to be affected. |
| 301 - 500 | Hazardous | Maroon | Health alert: everyone should avoid all outdoor exertion. |