DefinitionAnnual average (based on seasonal averages and daily measurement) ambient concentrations (microgram per cubic meter, g/m3) of PM2.5
NumeratorDays in which a county exceeded the national standard for ambient air concentrations of PM2.5.
Data Interpretation IssuesThis measure provides a general indication of the overall trend in annual PM2.5 concentrations. It may be affected by density and placement of monitors, and coverage will vary across the country and within states. It does not directly reflect exposure. Certain geographic areas, such as those near busy roads, are likely to have higher values.
It is important to understand that this indicator is not for use compliance determination with NAAQS or reasonable further progress toward attaining compliance.
The relationship between ambient concentrations and personal exposure is largely unknown and varies depending upon pollutant, activity patterns, and microenvironments.
Why Is This Important?Long-term exposure to fine particulate matter (PM2.5) is related to a variety of adverse health conditions. Each 10 ug/m3 elevation in PM2.5 is related to an 8% increase in lung cancer mortality, a 6% increase in cardiopulmonary mortality, and a 4% increase in death from general causes. (1)
Other ObjectivesCDC Environmental Public Health Tracking, Nationally Consistent Data and Measures (EPHT NCDM)