New Particulate Pollution Air Quality Index

Image:  Courtesy of the Virginia Department of Environmental Quality

You may soon notice some changes to the Air Quality Index (AQI). The AQI is a standardized color-coded scale used to describe health concerns associated with common pollutants such as ground-level ozone and PM2.5 (particulate pollution smaller than 2.5 microns in diameter). The AQI can range from 0 to 500. An AQI from 0-50 is green, for good air quality, whereas an AQI above 300 is maroon, meaning that air quality is hazardous. When the AQI is above 100 (orange or worse), air quality is unhealthy: first for sensitive groups of people, then for everyone as the values increase.

On May 6, the AQI changed for PM2.5 such that the breakpoint between green (good) and yellow (moderate) air quality has become more stringent. The Moderate category now begins when fine particle pollution concentrations reach 9 micrograms per cubic meter of air (the level of the updated annual air quality standard). Previously, the Moderate category began at 12 micrograms per cubic meter. EPA implemented this change to increase public health protection, consistent with evolving scientific understanding of the impacts of PM2.5 pollution. As a result of this, you may see air quality reach the yellow (moderate) AQI more frequently than in the past.

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