Environment and Sustainability / Air Quality


Air Quality


The Air Quality Index (AQI) is a measurement used to communicate the level of air pollution to the public and what associated health risks may be a concern. With increasing levels of pollution, the index number will increase. These numbers are determined by calculating the average of readings over a period of time. For Forsyth County, the air quality is calculated hourly at multiple monitoring stations. Each pollutant is measured and considered in the final index.

The AQI is calculated using standards set by the Clean Air Act (CAA). The standards relating to the CCA are focused on five common pollutants: particulate matter (PM), ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO). The EPA has established national air quality standards for each of these pollutants to protect public health.

Air Quality Index Levels

LevelIndex RangeExplanation
Good0 - 50Air pollution poses little or no risk.
Moderate51 - 100For some pollutants there may be a moderate health concern for a very small number of people.
Unhealthy for Sensitive Groups101 - 150The general public is not likely to be affected at this AQI range, but people with lung disease, older adults, and children are at a greater risk from exposure to ozone and from the presence of particles in the air.
Unhealthy151 - 200Everyone may begin to experience some adverse health effects, and members of the sensitive groups may experience more serious effects.
Very Unhealthy201 - 300This triggers a health alert signifying that everyone may experience more serious health effects. Everyone should avoid prolonged or heavy exertion.
The chart describes the AQI levels and associated index range. If an area reports an AQI of 25, then that day falls within the ‘Good’ range. However, if they report an AQI of 115, this falls within the orange category: ‘Unhealthy for Sensitive Groups' and so forth. Each level has suggested level of outdoor activity for certain groups of people.

Percentage of Days Where Air Quality is Above 100

  • There were zero days with AQI over 100 in 2017 in Forsyth County.
  • AQI values below 100 are generally thought of as satisfactory; it corresponds to the national air quality standard that the EPA has set to protect public health. When AQI values are above this threshold, the air quality is considered unhealthy.

Key Point: Air Quality Index Generally Good

  • In 2017, Forsyth county had 290 good days, 75 moderate days, and no unhealthy for sensitive groups, unhealthy, or very unhealthy days.
Notes on Data

This report has been produced to support grant writing efforts. As such, the validity and reliability of the data in this report has not been rigorously statistically tested. Forsyth Futures does not support the use of this data for specific programmatic planning. If you are interested in using data from this report for more rigorous purposes, please contact info@forsythfutures.org for a consultation on how best to proceed.

Data Sources