Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Environmental - Media - Air - Outdoor air pollution - Particulate matter Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource National and Local Trends in Particulate Matter Levels Subject The topic of the resource Using a nationwide network of monitoring sites, EPA has developed ambient air quality trends for particle pollution, also called Particulate Matter (PM). Trends from 1990-2008 appear on this website for PM2.5 and PM10. Under the Clean Air Act, EPA sets and reviews national air quality standards for PM. Air quality monitors measure concentrations of PM throughout the country. EPA, state, tribal and local agencies use that data to ensure that PM in the air is at levels that protect public health and the environment. Nationally, average PM concentrations have decreased over the years. Description An account of the resource <a target="_blank" href="http://www.epa.gov/airtrends/pm.html#pmnat" rel="noreferrer noopener">http://www.epa.gov/airtrends/pm.html#pmnat</a>