Air Quality – Particulate Matter 2.5 (409)


Indicator data are acquired from the Centers for Disease Control and Prevention (CDC) and Environmental Protection Agency (EPA) National Environmental Public Health Tracking Network (NEPHTN) Air Quality Data program. Data elements include the number and percentage of days with maximum 8-hour average ozone or particulate matter concentration over the National Ambient Air Quality Standard (75 ppb and 35 µg/L, respectively).

EPA provides modeled estimates of air quality using the Downscaler (DS) model, which uses a statistical approach to fuse monitoring data in areas where monitors exist, and relies on Community Multiscale Air Quality (CMAQ) modeled output in areas without monitors. DS modeled estimates are available by census tract centroid (the geographic center of the census tract). The county level estimates displayed here are crude and/or population weighted (Census 2010) averages created by aggregating the modeled census-tract level estimates. These county-level estimates may differ from the estimates available through the NEPHTN, which use actual monitor data when available, or the maximum value of the census tract modeled estimates for days and locations without monitors.

For more information on the data reported here, please visit the CDC’s Environmental Public Health Tracking Network: Ozone – Days Above Regulatory Standard or PM2.5 – Days Above Regulatory Standard Indicator Details web pages.


The National Environmental Public Health Tracking Network (Tracking Network) is a system of integrated health, exposure, and hazard information and data from a variety of national, state, and city sources. The Tracking Network provides information about the following types of data:
Health effect data: Data about health conditions and diseases, such as asthma and birth defects.
Environmental hazard data: Data about chemicals or other substances such as carbon monoxide and air pollution in the environment. 
Exposure data: Data about the amount of a chemical in a person’s body, such as lead in blood.
Other data: Data that helps us learn about relationships between exposures and health effects. For example, information about age, sex, race, and behavior or lifestyle choices that may help us understand why a person has a particular health problem.

State and county level Tracking Network data is available to view or download through the Map Viewer or through the Indicators and Data web page.


Race and Ethnicity
Statistics by race and ethnicity are not provided for this indicator.